Author: spqr

Smartphone cameras, pixel-binning, and the art of megapixel hype

/ spqr / 1 Comment

Many smartphones are now marketed as having at least one camera with a ridiculous amount of megapixels. The iPhone 14 Pro has 48MP, the Samsung Galaxy S23 has 200MP. Is it just too much? The answers is yes, and some would argue it’s more of a marketing hype than anything else. I mean who doesn’t want to take a 48MP or 200MP image? Well, most people may try it once, but many won’t routinely use it, and the reasons why are varied. First, let’s look at the technology.

Smartphone sensors are no different to any other sensors, they are just usually smaller than many conventional digital camera sensors. The sensors contain a bunch of photosites, so no different there. But there are limits to the size of sensor that can be used inside a smartphone, made more restrictive by the fact that many smartphones now have 2-3 rear-facing cameras. Higher resolution means that more photosites need to be crammed into the sensor’s surface area. The iPhone 14 Pro has a wide angle camera with a 48MP resolution. It uses a 1/1.28” sensor, which is 10×7.5mm in size with a photosite pitch of 1.22µm, which is extremely small. Typically smaller pixels have a harder time getting light than larger ones, leading to some issues in low-light situations. So smartphones typically get around this by creating reduced resolution images with “bigger” pixels that are created by means of photosite binning (or pixel binning if you like).

Fig.1: Pixel binning (2×2) with the iPhone 14 Pro – converting 48MP to 12MP by merging

Photosite binning artificially groups smaller pixels into larger ones, potentially boosting the amount of light that can be gathered. The example in Figure 1 shows part of the quad-Bayer sensor of the iPhone 14 Pro. It illustrates how a 12MP is generated from a 48MP sensor. Here four photosites (2×2) are binned from the sensor, producing a 12 megapixel image, i.e. 48÷4=12. The Samsung Galaxy S22 Ultra takes 108MP images, and also defaults to 12MP, but instead of using a 2×2 binning, it uses what Samsung calls “Nonacell” technology”, merging 3×3 photosites into a super pixel. So the photosites, which have a pitch of 0.8µm, are merged to form a 2.4µm super-pixel. Figure 2 shows how a true 48MP images is create via some sort of remosaicing algorithm (pixel rearrangement algorithm).

Fig.2: The iPhone 14 Pro Quad—48MP bayer sensor to 48MP image via a simple remosaicing algorithm

The 200MP Samsung ISOCELL HP-3 1/1.14” sensor takes it a step further. It uses a new “Tetra2” binning mechanism, with 0.56µm photosites. It can produce 200MP, 50MP, and 12.5MP images (shown in Figure 3). In the first stage 2×2 binning is used on the sensors 0.56µm photosites, producing a 1.12µm “super-photosite”, and a 50MP image. Then another round of 2×2 binning is performed, creating a 2.24µm “super-super-photosite”, and a 12.5MP image.

These high resolution sensors are typically only used at full-resolution in bright scenes, reducing to a lower resolution in dark conditions. The idea of binning is to allow smartphone cameras to become more intelligent, choosing the optimal resolution based on the photographic conditions. Of course the question is, does anyone need 50 or 200MP images? As with all technology, there are drawbacks.

Fig.3: Conversion between the ISOCELL HP-3 sensor and 200MP, 50MP, 12MP

Firstly, in the world of digital cameras, 100MP or thereabouts is usually found on a medium format camera with a sensor size of about 44×33mm, e.g. Fujifilm GFX 100S. These cameras are designed to take high resolution images, with sensors containing photosites of a reasonable light-gathering size (e.g. 3.76µm). Now compare the photosite area of this medium format camera, at 14µm2, with that of the Samsung Galaxy S22 at 0.64µm2 – 22 times more light gathering surface area. There is no comparison. Digital cameras also generally use high-quality lenses, with a lot more light gathering potential than those found on smartphones – when it comes to optics, smaller is always marred in compromises.

The process of binning pixels may also introduce artifacts, whether it be a small change in the overall colour of the image, or perhaps blurring artifacts – it really depends on the technology, algorithms, etc. Even remosaicing is a little more challenging, primarily because the different colours are further apart. So there isn’t really 4× more detail in 48MP mode than there is in 12MP mode. Then there is storage. 200MP image files should be large, but due to some sort of compression wizardry, the 12240×16320 images are reduced to files about 30MB in size, which is quite reasonable. Supposedly RAW (DNG) images can take up to 120MB. So storage is an issue. Also, what do you really need a 200MP camera for?

So if the mainstay is a quasi-12 megapixels why do manufacturers waste effort in creating hyper-megapixel smartphones? Perhaps for that one ideal 200MP shot? That perfect sunset while on vacation in Iceland. But what would you do with a 200MP image? Make a print to hang up on the wall? More megapixels does allow for better digital zooming, but the more likely case is that manufacturers know that megapixels matter to consumers, a situation they themselves have hyped up over the past two decades.

Further reading:

Quad Bayer sensors: what they are and what they are not (2019)

Feininger on black-and-white photographs

/ spqr / Leave a comment

“Through absence of color, three-dimensionality and motion, the black-and-white photography is ipso facto ‘unnatural’. It expresses reality symbolically: gray tone values instead of color, two-dimensional projection (perspective) instead of space, blurredness or single-phase instead of constant motion. It is ‘symbolic’ in the same sense that speech and writing are, where sounds (words) are symbols for objects and conceptions, and signs (letters) are symbols for sounds (words). Photography means ‘reproduction’ only in the rare cases where the rendering of a two-dimensional, black-and-white object is the aim; otherwise it must be called a translation.”

Andreas Feininger, Feininger on Photography (1949, pp.195-196)

Vintage camera makers – The origins of Zeiss Ikon

/ spqr / Leave a comment

Zeiss Ikon was a part of the Zeiss empire emerging in Dresden in the 1920s as the conglomeration of six German optical companies. But its origins were likely in 1909 with the creation of the Internationale Camera A.-G. (ICA) in Dresden. It was initiated by Carl Zeiss and resulted in the merging of four companies: Hüttig, Krügener, Carl Zeiss Palmos, and Wünsche. This was likely precipitated by overproduction in the photographic industry in 1908.

  • Hüttig AG (1862) − One of the larger camera makers of the period. Produced the first single-lens-reflex camera, the Zeus-Spiegel-Kamera.
  • Krügener − Maker of cameras with magazines.
  • Wünsche AG (1887) − Camera maker: roll film, sheet film, plate film. Notable cameras included the “Bosco” and “Ada” mirror cameras, and the Mars detective camera
  • Carl Zeiss Palmos (1902) − Founded in 1900 as an independent camera company, then absorbed by CZJ.

In 1912 the small Swiss camera maker Zulauf joined the group. After rationalization, ICA produced a number of cameras continuing some of the lines of the founding companies. New products were also added. In 1926 Zeiss Ikon was formed. It was comprised of four companies:

  • ICA – Internationale Camera A.-G. (Dresden, 1909)
  • Optical Institute CP Goerz A.-G. (Berlin, 1888) − Camera and lens manufacturer
  • Contessa-Nettel A.-G. (Stuttgart, 1919) − Camera manufacturer created from the merger of Contessa Camerawerke Drexler & Nagel and Nettel Camerawerk.
  • Ernemann-Werke A.-G. (Dresden, 1889) − Camera maker
The evolution of Zeiss Ikon

To emphasize the focus on photography, the word Ikon was used, the German word for the Greek εἰκών meaning image. The use of Zeiss indicated an affiliation with the parent company in Jena. In 1927/28 two others companies joined the fold:

  • AG Hahn für Optik und Mechanik (Ihringshausen)
  • Goerz Photochemisches Werk GmbH (Berlin)

Over the years, a lot of streamlining was done, slimming down the company from 100 basic camera models in 1927 to 14 basic models in 1938. One of the most important products to come out of Zeiss Ikon was the Contax system, which appeared in 1932. This was followed by the Contax II in 1936. There were many cameras in the 1930s – Ikonta folding cameras, Baldur (a box camera), Contaflex (twin-lens reflex). From 1940 the German economy pivoted to a war economy. The end of the war brought damage to many of the factories, and in 1948 the company was expropriated and converted into a state company (using the designation VEB, meaning Volkseigener Betrieb or publicly owned enterprise). In the same year, the new western headquarters of Zeiss Ikon was established in Stuttgart.

Over the next few years Zeiss Ikon in East Germany changed its name quite a lot:

  • 1945 − VEB Zeiss Ikon Dresden
  • 1948 − VEB Mechanik Zeiss Ikon
  • 1951 − VEB Optik Zeiss Ikon
  • 1955 − VEB Zeiss Ikon
  • 1958 − VEB Kinowerke

In 1959 of course, VEB Kinowerke was folded into VEB Kamera-und Kinowerk Dresden, the precursor to VEB Pentacon Dresden.

In West Germany, the company continued to be known as Zeiss Ikon. In 1956 the Carl Zeiss Stifung, (the parent company of Zeiss Ikon), bought Voigtlander. It continued to be operated as a separate company until 1965, when it was merged with Zeiss Ikon to form Zeiss Ikon-Voigtlander. It produced mostly different products to its eastern brethren, although there were similarities. For example both companies made renditions of the Contax camera. In 1972, Zeiss Ikon-Voigtlander ceased production of cameras.

❖ Zeiss Ikon in West Germany was established at the Contessa-Nettel factory in Stuttgart, the only one of Zeiss’s major facilities not under Soviet control.

Vintage digital cameras – What is the biggest problem?

/ spqr / Leave a comment

Vintage 35mm film cameras can survive for decades. You can pick up a camera from the 1960s and if its fully mechanical, there is a good chance it will still be fully functional. Vintage cameras that require batteries, e.g. for the exposure meter, or contain electronics are more of a hit and miss situation. The problem is that no one really can ascertain how well electronics age. Some age well, others don’t. Digital cameras are another thing altogether.

Anyone who has used digital cameras for the past 20 years likely has a few of these “zombie” cameras sitting in a cupboard somewhere. Cameras are upgraded, with their predecessors effectively “shelved”. The reality is that for the most part, digital cameras beyond a certain age just don’t hold much value (unless they are from Leica). One problem with vintage digital cameras is that things can just stop working. I have an old Olympus E-PL1 MFT camera. I haven’t used it in a while, and when I tried it today, it displayed a blinking red “IS-1” indicator. This basically means that the image stabilizer has failed (noticeable when the camera is first turned on because the anti-dust mechanism makes a rattling noise). That’s inherently an issue with electronics, things can just stop working, and fixing them on an old camera is often just not financially viable. It’s basically digital junk.

It’s dead Jim!

But the bigger problem is actually the battery. Some manufacturers have decided over the years to change the type of batteries used in their cameras (for many reasons). When a camera becomes legacy, i.e. is no longer supported, there is a good chance that the manufacturer will stop making the associated batteries. The E-PL1 was introduced in 2010, and although the battery in my camera still works, it is not possible to buy Olympus BLS-1 batteries for it anymore. It is also not really possible to determine what the status of existing batteries is – measuring the number of battery cycles is not easy or even possible (unlike laptop batteries). One way is to charge the battery, and take photographs until it drains, but tedious is an understatement. A battery will typically last between 300-500 recharge cycles.

The result is a vintage digital camera that may still work well, but ultimately needs a new battery. You could try the gambit of 3rd party batteries, but there really isn’t any way of knowing what battery will actually work, because they don’t usually come from verifiable battery makers (often resulting in slight fluctuations in the voltage provided to the camera). Yes, you can get replacement batteries from companies like Duracell (via DuracellDirect.com), however this company is not owned by Duracell, but rather PSA Parts Ltd. And these batteries are not exact replacements. For a real analysis, check out this article by Reinhard Wagner who dissects some off-brand Olympus BLN-1 batteries (it’s in German, but is easy to translate).

So what does this mean? Essentially if you want to use a camera long-term, make sure you have a good amount of spare batteries, i.e. anyways purchase at least one spare battery when purchasing a new camera. Also check the date on the batteries, as they made need replacing as they age. In all likelihood, nobody is going to be using vintage digital cameras in 50 years time, but they still might be using film ones.

P.S. The digital “age” of a camera is sometimes counted using the idea of “shutter actuation’s“. This is basically a count of how many photos have been taken. A modern mirrorless camera will have shutters rated at around 100-150K. Most cameras likely won’t come anywhere near that count, so they aren’t really a valid notion, except perhaps to indicate how much a camera has been used.

Should you fix your own film camera?

/ spqr / Leave a comment

Certain vintage cameras can be expensive, but there are sometimes opportunities to buy these cameras in a malfunctioning or “non-working” form for a reasonable price. A good store will tell you what is wrong with the camera, but the problem is that there aren’t exactly a lot of places where you can get film cameras fixed, and of those, they are often focused on a particular brand of camera. Fixes that involve digging into the guts of a camera are inherently marred with problems. A while back I bought an Exakta TL VX1000 camera, because it was cheap, but mostly for the lens. When it arrived it seemed to work, except the film-transport lever had been snapped in half. So I bought a replacement lever, and thought it would be a simple process to fix it. It wasn’t and although I replaced the lever, something else broke (a spring). I should have had a better understanding of the inner workings of Exakta cameras.

The Nikon F, a fully mechanical camera (and Nikon’s first SLR) has 918 mechanical pieces.

In reality, very few cameras are easy to fix. Fully mechanical cameras are filled with parts, and cameras with electronics are even trickier – i.e. it may be possible to source a donor part, or even 3D print a part, but recreating 50 year-old electronics is another thing altogether. You need the appropriate tools, and access to parts and assembly diagrams, e.g. the Nikon F3-P parts diagram posted on Japan Camera Hunter. The easiest repairs are obviously cosmetic issues – replacement of leatherette, battery covers, etc. or replacing light seals. There is also the issue of cost – fixing a vintage camera can often become expensive, especially as parts often have to be salvaged from a “donor” camera. Even the simplest parts, like springs, can be challenging to find, considering they may be decades old (springs have to be the right size and have the right tension).

The Nikon F3, with semi-automatic exposure control, was not any less complex than film cameras.

If you are really interested in doing your own internal camera repairs, I suggest reading though the information below. For cameras that are rare, I would recommend having them fixed at an experienced repair facility. In Canada, probably one of the best known camera repair spots is Paramount Camera Repair, in Saskatoon. There is also Factory Cameras in Vancouver.

DIY Camera/Lens Fixing Resources:

Do the aesthetics of a camera impact its usability?

/ spqr / Leave a comment

The useful and the beautiful are never far apart.

Periander

There is a condition known as the aesthetic-usability effect, whereby users perceive objects with more aesthetically pleasing designs to be easier to use than less aesthetically pleasing designs. Humans tend to be drawn towards nicer looking things. Take for example the aesthetic appealing atomic coffee maker. The design is attributed to Italian Giordano Robbiati, and was born in the 1940s. It ozzed aesthetic appeal, and was very popular (and still is). People likely presumed that something that looks nice probably works well. Its curved form likely melded well with the fluidity of coffee.

The atomic espresso maker.

People of course use aesthetics to judge appeal and perceived usability. Something that looks will likely work well. It is no different with cameras. There are cameras that are very aesthetically pleasing, and work extremely well, from the perspective of the layout of controls, or even how easy it is to add/remove a lens.

One of the ugliest cameras around appears to be the Konica Aiborg, more often referred to as Darth Vader camera. A 35mm camera which appeared in 1991, its name a blend of AI and cyBORG. It was bulky, had poor ergonomics, and just seemed an odd design from an aesthetic point-of-view. It’s quite possible that curved surfaces just don’t translate well to cameras, the same as they do to espresso makers. In fact all the curved surfaces do is detract from the aesthetic appeal of the camera, and may ultimately affect its usability.

Luke, I am you father (Konica Aiborg)

What is the most aesthetically pleasing 35mm camera? Well that likely is in the eye of the beholder… and whereas many people might agree about an ugly camera, beautiful cameras are harder to pin down. With film cameras, I am certainly partial to cameras that have clean lines, but that may result from the fact that the pictures themselves are rectangular in form. I do like the Canon 7s, the Olympus Pen F and just about any Ihagee Exakta Varex camera. With digital cameras I inherently lean towards those that mimic the lines of previous film cameras.

The Olympus Pen-F

In my opinion, one of the nicest 35mm cameras is the Olympus Pen-F half-frame camera. It has beautifully clean lines, lacking the “triangular hat” of a regular 35mm SLR (because it uses a Porro prism), and placing the shutter speed dial on the front of the camera. The camera is small, and compact, ergonomic to use, and almost minimalist.

Should you buy a superfast lens?

/ spqr / 1 Comment

A superfast lens, is one with a very large aperture, say f/1.2 to f/1.0 (whereas an ultrafast is typically sub-f/1.0). The craze for super-fast lenses began in Japan in the 1950s, with the Zunow 50mm f/1.1 appearing in 1953. There was a lull in the latter decades of the 20th century, but the last ten years has seen a resurgence of these uber-fast f/1.2 and larger aperture lenses. There is always a lot of hype about these lenses – they are expensive, and supposedly offer some sort of nirvanic photographic experience. The question is, should you spend the money to indulge in super-fastness? First let’s look at some aspects of super-fast lenses that make them attractive.

“Do you need a superfast lens” ?

The faster the lens is, the more light it lets in

The larger the aperture, the more light that is let into the lens, and in photography, light is good. Moving from a f/1.8 to a f/1.2 lens provides 1.17 stops more light (where one stop doubles the light). For example a 50mm lens with a speed of f/1.8 has an effective aperture of 606mm2. Another 50mm lens with a speed of f/1.2 has an effective aperture of 1363mm2.

If we consider shooting at f/1.8 versus f/1.2, the larger aperture will mean the ability to shoot at faster shutter speeds – if we assume a constant ISO, then increasing the aperture by 1.17 stops means the difference between shooting at 1/500 at f/1.8 and 1/1250 at f/1.2. The second thing is that assuming the shutter speed is fixed, you can shoot at a lower ISO setting – e.g. at a shutter speed of 1/500 it means it means an ISO difference between 400 and 160. However modern sensors work really well at high ISO settings, so perhaps the advantage of a fast lens isn’t as critical?

Faster lenses produce better aesthetics

If it’s one thing that large aperture lenses are good at, it’s aesthetics. This is because the lower the f-number, the shallower the depth of field (DOF). Shallow DOF means a blurrier background, and theoretically better bokeh. However bokeh is a natural phenomena, and relies on the optical nature of the lens, the scene, the type of light, and distance to subject. In addition, a shallow DOF also means less of the image is in focus. It’s a double-edged sword.

Not all that glitters is gold

Of course super-fast lenses are not perfect. They have three things going against them – they are large, heavy, and expensive. They are large and heavy because of the increased amount of glass, and in auto-focus lenses, a larger focusing mechanism is required to deal with the extra glass. I have talked previously about why vintage super-fast lenses were so expensive, and in reality the same basic reasons can be attributed to super-fast digital lenses. For example the Fujifilm XF 50mm f/1.0 R WR lens sells for C$2,000, and is a whopping 845g in weight, almost dwarfing any Fuji camera it is attached to. The other issue with super-fast lenses has always been that they aren’t really that sharp until they are stopped down somewhat. The Fuji 50mm f/1.0 reviews well, but even then some reviewers note that it isn’t that sharp until stopped down to f/2.8 or smaller. But reviews are subjective, and so you really have to test the lens to see if it fits your needs.

Brand or third-party lens?

There is also the dilemma of which super/ultra fast lens to buy. There are a lot of 3rd-party lens manufacturers that produce these lenses at a reasonable cost. I mean you can buy the Meike 50mm f/0.95 for about C$400, or the TTArtisan 50mm f/1.2 for about C$140. The Meike actually gets really good reviews. The reality is that 3rd-party lenses offer a good quality for the price, even better than could be found on the vintage market. Of course the Fuji 50mm f/1.0 is in a class of its own, offering autofocus for a f/1.0 (most lenses of this speed are manual focus), and exceptional bokeh.

So should you buy a super-fast lens? Well, perhaps it boils down to whether you really need more light? This may mean you shoot a lot in low-light conditions, or in a case of the Fuji 50mm f/1.0, a superlative lens for portraiture. For a further foray into these lenses, check out “Are modern ultrafast lenses useful?“.

✿ The number of stops difference between two apertures A and B can be calculated by first finding C=A/B. The number of stops difference is then log(C)/log(sqrt(2)). So the difference between f/1.8 and f/1.2 is 1.17 stops.

What is a pentaprism?

/ spqr / Leave a comment

The first 35mm SLR camera, the Ihagee Kine Exakta, used a horizontal waist-level viewfinder. This was not unusual for the period, as there was no other means to view a picture through the camera at an eye-level (that wasn’t a rangefinder camera). The problem is that the image viewed would be flipped left-to-right. This would be rectified by the introduction of the first production pentaprism camera in 1947, in the guise of the Italian Rectaflex. The technology became more mainstream with the introduction of the Zeiss Ikon Contax S in 1949 (although waist-level viewfinders would still be dominant until the mid-1950s).

Fig.1: Early SLRs did not have a pentaprism, but instead required the photographer to look through a waist-level viewfinder

A pentaprism or pentagonal prism is a five-sided glass prism (although technically while the cross-section of a pentaprism is bound by five sides, it actually has seven or eight). Prisms were already being using in the Victorian era to design telescopes and binoculars. The use of a pentaprism in optics stems from an invention by a Captain Charles-Moÿse Goulier (1818–1891) of the French engineer corps in 1864, a “triangulation prism telemeter” [1]. It was a device with twin sighting paddles, connected by wire 40 meters long to establish a fixed baseline. Each paddle contains a five sided prism to give simultaneous orthogonal views. It may have been the first use of pentagonal prism in optics.

Fig.2: The pentaprisms used in Goulier’s 1964 invention (adapted from [1]).

This form of conventional pentaprism, sometimes referred to as a flat-roof or Goulier prism, is characterized by a 90° deviation angle (Fig.3(1)), i.e. it deviates a beam of light by 90°, reflecting the beam inside the prism twice. It is comprised of two reflective faces (Fig.3(1)b,c), arranged at 45° between them and two faces orthogonal to each other (Fig.3(1)a,d). The two surfaces performing the reflections are coated to provide mirror surfaces (e.g. silvered). The two opposite transmitting faces are often coated with an anti-reflective coating. In imaging applications this pentaprism will neither invert nor reverse an image, e.g. Fig.3(1). In the context of an SLR this still holds true, because the image is flipped as it passes through the lens and it is this flipped image that passes through the prism. So in the context of the ‘flippedi image, it is neither inverted or reversed. However, compared to the original object in front of the lens, the image viewed at the eyepiece is reversed left-to-right. Prior to the end of WW2, conventional pentaprisms were commonly used in telescopes, binoculars, and military equipment such as rangefinders.

This is illustrated in Fig.3(3) where the object F passes through the optical system of an SLR. The F is flipped by the lens and this flipped version of the F passes through the prism. The image viewed at the eyepiece is neither inverted nor reversed from that projected on the mirror. However compared to the original F, the image is reversed left to right.

Fig.3: The flat-roofed (conventional) pentaprism: (1) a simple optical path, (2) a breakdown of the angles, and (3) used in the context of an SLR optical system.

The more complex pentaprism found in the majority of SLR cameras is the roof pentaprism which reverses an image from left-to-right. It is similar to a conventional prism, but with the addition of two silvered “roof” surfaces. The concept of a roof prism was created by Italian astronomer Giovanni Battista Amici (1786-1863) in the mid-1800s. His Amici-roof prism, also known as a right-angle roof prism, was capable of reverting and inverting the image of an object while bending the line of sight through a 90° angle (Figure 4). It was used in various types of telescopes.

Fig.4: The Amici-roof prism.

A roof prism is a prism containing a section where two faces meet at a 90° angle, resembling the roof of a building. Reflection from the two 90° faces returns an image that is flipped laterally across the axis where the faces meet. The first large scale use of a roof pentaprism may have been in binoculars, like the Pentaprisma Binocle 7×24 made by Hensoldt & Söhne (Wetzlar) introduced in 1900. An earlier version of the binoculars (1897) used a flat pentaprism attached to a right-angle prism with a roof (like an Amici-roof prism). This arrangement was denied a patent in Germany, due to a conflict with a Zeiss patent (DE77086, which used a Porro-prism), however was granted a patent in Great Britain (GB15806, 1898). The newer version of 1900 had a dialytic (split) optical system where the pentaprism had a roof edge (Figure 5).

Fig.5: Hensoldt & Söhne’s ‘Pentaprism binoculars’ (1900)

In an eye-level SLR, the roof pentaprism is inserted between the focusing screen and the viewing eyepiece. The roof pentaprism, by introducing extra reflecting surfaces, shows the object both upright and with the right and left sides in their proper place. The bottom surface of the pentaprism may form the focusing screen, or the latter may be positioned directly below the prism. The focusing screen may be of several different kinds, including plain ground glass, to various combinations of clear glass, ground glass, or micro-prism focus finder.

Fig.6: An example of light passing through a roof-pentaprism

The light passing through a roof-pentaprism undergoes three separate reflections in order that the image is seen both right way up and right way round. The image enters the prism right way up, but laterally reversed, so that as the image must be turned again through 90° to allow it to be viewed at eye level, it must be reflected twice to keep it right way up. The third reflection has no effect on the vertical aspect of the image but it merely used to reverse the image laterally so that it is seen right way round.

Fig.7: Image passage through an SLR camera using a roof-pentaprism

The basic history of the pentaprism as it relates to the SLR can be found in a separate post. But a summary is provided below. A timeline of early SLR pentaprisms:

  • 1933 − Kurt Staudinger issued a patent for a reflex device, i.e. a penta-mirror
  • 1937 − Zeiss Ikon (Germany) begins work on the Syntax, a camera with a pentaprism. Patents exist for the concept, but the prototypes, ca. 1944 were destroyed during the war.
  • 1948 (Sept) − First commercially produced SLR with a roofed pentaprism, the Rectaflex (Italy). An earlier 1947 prototype used a flat pentaprism.
  • 1949 (Sept) − Zeiss Ikon (GDR) introduces the Contax S, the second SLR with a pentaprism, essentially recycling the Syntax.
  • 1949 − ALPA introduces the ALPA Prisma Reflex, a pentaprism with a 45° view. ALPA would not introduce a normal perpendicular view until the Model 6c (1960).
  • 1952 (Sept) − Wrayflex receive a patent for an SLR with a “pentagonal prism” which was never produced. The first Wrayflex with a pentaprism was the Wrayflex II (1959).
  • 1955 − The first Japanese SLR with a pentaprism, the Miranda T.

Note that a pentaprism is different to a penta-mirror, which instead of a glass prism uses three mirrors to perform the same task. Using a glass prism has definite benefits over mirrors. Changes in light direction in a prism is based on the notion of total reflection, which means reflectances of close to 100% can be achieved, while silver mirrors lose at least 10% to absorption losses. A glass prism is also better because the refractive index of glass causes a shortening of the light path.

Notes:

  • Goulier’s prism is sometimes known as the Prandl prism (or even the Goulier-Prandl prism), and is often cited as such, particularly in German literature. Now a cursory search will find very little, but digging a little deeper finds a paper published in the German journal Zeitschrift für Vermessungswesen (Journal of Surveying) in 1890, by an Alexander Prandtl [2]. Prandtl (1840-1896) was a professor at the Royal Bavarian Central Agricultural School in Weihenstephan specializing in dairy farming. But the paper describes a 4-sided prism, similar to Goulier’s prism except the extra side between the two surfaces meeting at 45° is missing. The other issue is the fact that Goulier’s prism was described 26 years previously. Prandtl’s real claim to fame was developing the first continuously operating milk centrifuge.
  • Hensoldt & Söhne created their first product, a rangefinder using a roof prism in 1892. The company would go on to develop the Hensoldt roof prism (DE180644, 1905) which required no mirroring, and had no axis offset, allowing for straight binoculars. In 1938 the Carl Zeiss Foundation would take a majority share in Hensoldt. It is entirely possible that this mechanism formed the basis of the work done on the Zeiss Syntax SLR in the late 1930s and early 1940s.
Fig.8: A depiction of the Prandtl prism (adapted from [2]).

Further reading:

  1. Barnard, F.A.P/, “Prism Telemeter”, Report on Machinery and Processes of The Industrial Arts and Apparatus of the Exact Science, p.589-592 (1869)
  2. Prandtl, A., “Ein neues Instrument zum Abstecken von rechten Winkeln” (A new instrument for marking out right angles), Zeitschrift für Vermessungswesen, 19, pp.462-467 (1890)

Updated: November 27, 2025.

Smartphones and digital cameras are like chalk and cheese

/ spqr / Leave a comment

The internet is full of articles suggesting smartphone cameras are better than actual digital cameras. Sure the smartphone market is booming, and they do take good pictures, but it’s really not possible to accurately compare them to digital cameras. It’s like saying to an astronomer that they could get the same quality astronomical image using a full-frame or medium format camera?

In late 2022 the worlds largest digital camera was unveiled at SLAC National Accelerator Laboratory in California. By the end of 2024 it will be installed at the Vera C. Rubin Observatory in Chile, and will be used in a 10-year project called the Legacy Survey of Space and Time to help unlock the mysteries of the universe. The composite sensor is comprised of 189 individual 16MP sensors, each 42mm2 in size, for a total resolution of 3.2 gigapixels. It’s largest lens has a diameter of 1.57m. Overall the focal length is 10.31m, with a speed of f/1.23. The camera will take 200,000 pictures per year.

This camera is massive. The individual photosites are 10×10μm in size – and large photosites mean that an abundance of light can be captured in such a ultra-low light environment (the sensors will be able to spot objects 100 million times dimmer than those visible to the naked eye). You could never achieve this with any sort of medium format 100MP 44×33mm camera… it’s just not possible. So why then do people still harp on about 12MP smartphone cameras being able to produce the same quality image as a 46MP DSLR?

Researchers at SLAC National Accelerator Laboratory are nearly done with the LSST Camera, the world’s largest digital camera ever built for astronomy. Roughly the size of a small car and weighing in at three tons, the camera features a five foot wide front lens and a 3,200 megapixel sensor that will be cooled to 100°C to reduce noise. Once complete and in place atop the Vera C. Rubin Observatory’s Simonyi Survey Telescope in Chile, the camera will survey the southern night sky for a decade, creating a trove of data that scientists will pore over to better understand some of the universe’s biggest mysteries, including the nature of dark energy and dark matter. (Jacqueline Ramseyer Orrell/SLAC National Accelerator Laboratory)

✽ Note that the size of the effective aperture on a smartphone lens such as the wide-angle 6.86mm (f/1.78) on the iPhone 14 Pro Max is 3.85mm. From a full-frame equivalency point-of-view, this is a 24mm lens with a speed of f/6.3. No one produces 24mm FF lenses with such a slow speed, but as an example, a Sony 24mm f/2.8 has an effective aperture of 8.57mm. Small lenses just aren’t as effective at capturing light – it’s basic physics. Of course the other big issue with smartphone cameras is that the lens elements are mostly constructed of moulded plastic (as opposed to glass).

So you want to upgrade from a smartphone camera?

/ spqr / Leave a comment

Most people who use smartphones have little, if any, idea about things like aperture and shutter speed. They just use their smartphone camera to take pictures, and tend to ignore functional specifics. Settings are whatever the smartphone deems appropriate for the situation. For example clicking on ×0.5 in the Camera app on a modern iPhone will get you an image automatically taken with the ultra-wide camera. Yes you have some control over things, or more control when using a 3rd-party app, but generally these things don’t matter to most people. The future will bring more AI to smartphone cameras to produce so-called “perfect” photos – and if you like point-and-click photography, that’s fine. But sometimes that’s just not enough.

So what happens when you are intrigued enough to upgrade from a smartphone to a “real” digital camera? Should you run out and buy a full-frame (FF), or should you opt instead for a compact camera? To figure out what you really need, you have to first determine why you want to upgrade. Is it because you want to learn more about photography, or perhaps you want better control of the pictures you take? Or because you feel hamstrung using smartphone a camera and want more megapixels, better optics, or just a better way of taking pictures. Regardless of what people say, a smartphone camera will never provide the same sort of control, or image quality of a dedicated camera. There are many reasons for this, but the big ones are optics, storage space, and battery life. But this isn’t a post about that, here I want to consider options for “upgrading” from a smartphone camera (I’ll cover those in a separate post).

Upgrading from a smartphone to a compact – some specs.

Once you have figured out why, then we move onto what sort of photography you will be focusing on. Do you just want a camera for better travel photographs, or are you interested in landscapes? Or perhaps macro-photography? At this stage it is best to make a list of things you would like to achieve with a digital camera. Some of these things will help you narrow down the type of camera is best for you. For instance if you like street photography, then the best camera might be a compact camera like the Ricoh GRIII/IIIx, or the Fujifilm X100V. Compact cameras offer several advantages over smartphones – a larger sensor is the most obvious benefit, while physical controls and ergonomics offer a more tactile shooting experience. Most compact cameras now also use touchscreen interfaces, making them very accessible. These cameras generally have a fixed focal length lens, and a sensor somewhere between 20-24MP (which is more than adequate). Compact and inconspicuous cameras are perfect for street photography – the last thing you want as a street photographer is lugging around a huge hunk of a camera – it makes you stick out like a sore thumb.

Some of the benefits of digital cameras

If you want a better camera for travel, then a compact is good as well, as are crop-sensor cameras. Here cameras with mirrorless APS-C sensors have become popular, like the Fuji-series of cameras. Cameras for travel have to be versatile, compact and light – the new Fujifilm X-S20 weighs only 491g (without lens) – add a general purpose Fujifilm XF 23mm lens at 180g, and you get a total of 671g (and frankly you don’t need to travel with a cornucopia of lenses). You could also go for a smaller Micro-Four-Thirds sized sensor, which provides a camera with an even smaller form-factor. Now you could even go for a full-frame (FF) sensor, but I would not really recommend it for people upgrading from a smartphone. They are generally heavy, ostentatious (for travel anyway), and are not a good fit for novice photographers. Learn on something smaller before deciding on whether you really need a FF (or buy an inexpensive, older FF camera). Then there are those that want a more specialized set-up for landscapes, macro, sport or wildlife. As these types of photography are much more specialized, requiring specialized lenses, I would not jump straight into them. They can be expensive, and often need a good amount of experience to be used in an effective manner.

Choosing a camera is about what you are interested in photographing, budget, future expandability (if that is important), camera ergonomics (it has to feel right to use, or you will hate using it), diversity of lenses, and a myriad of other things. Decisions on choosing a camera are often made based on sensor size, or ultimately megapixels, but upgrading should not be purely about megapixels. Most good cameras have around 24-26 megapixels, which is more than adequate. You don’t need 40 megapixels – really, you don’t. Choice of sensor size, Micro-Four-Thirds (MFT)/APS-C/FF, is often a factor of the type of photography a person is interested in. Every different camera sensor has its own advantages and disadvantages.

If you want to delve into the world of real cameras, it doesn’t have to be expensive. Start with a used camera, with a single, versatile lens. You can add other lenses as required, and even add vintage lenses from 35mm film cameras. For instance you can readily purchase vintage telephoto lenses for very little $. There are an abundance of them out there. They require manual focusing (that’s a good skill to learn), but it’s a good way to find out if you like wildlife photography before going out and spending thousands of $. There is no need to run out and buy the latest and greatest. When everything is taken into consideration, upgrading from a smartphone camera to an actual digital camera allows for increased flexibility and enhanced artistic opportunities.