Every movie made publicity stills, and Rear Window was no different. The interesting thing about some of these shots, is the camera used. The two shots in question include Grace Kelly shooting Jimmy Stewart with a Korelle Master Reflex. What I don’t quite understand is why this particular camera was chosen, as opposed to the actual camera used in the movie, the Exakta VX.

This camera was the US version of the Meister-Korelle, a 6×6 SLR which used 120 film. It was the last version of the Reflex-Korelle, a camera made by VEB WEFO (Werkstätte für Feinmechanik und Optik), a short-lived, state-owned company in East Germany. The original Reflex-Korelle was designed by Franz Kochmann released in 1935. Production of the camera lasted from 1950 to 1952. The camera’s basic design and configuration was carried forth in the cameras such as the Exakta 66, Praktisix, and Pentacon 6.

As to why this camera? Likely because it seems to have been a camera commonly used by cinematographers. The lens? Hard to completely decipher, and by no means one of the “standard” lenses listed with the camera. Companies like Astro-Berlin did provide lenses for the Master Reflex, as cited in publications like American Cinematographer. Or perhaps a Kilfitt?

Further reading:

• Meister-Korelle – zeissikonveb.de

“For me, capturing what I feel with my body is more important than the technicalities of photography. If the image is shaking, it’s OK, if it’s out of focus, it’s OK. Clarity isn’t what photography is about.”

Daido Moriyama

What is sensor resolution? It is not the number of photosites on the sensor, that is just photosite count. In reality sensor resolution is a measure of density, usually the number of photosites per some area, e.g. MP/cm². For example a full-frame sensor with 24MP has an area of 36×24mm = 864mm², or 8.64cm². Dividing 24MP by this gives us 2.77 MP/cm². It could also mean the actual area of a photosite, usually expressed in terms of μm².

Such measures are useful in comparing different sensors from the perspective of density, and characteristics such as the amount of light which is absorbed by the photosites. A series of differing sized sensors with the same pixel count (image resolution) will have differing sized photosites and sensor resolutions. For 16 megapixels, a MFT sensor will have 7.1 MP/cm², APS-C 4.4 MP/cm², full-frame 1.85 MP/cm², and medium format 1.1 MP/cm². For the same pixel count, the larger the sensor, the larger the photosite.

It can also be used in comparing the same sized sensor. Consider the following three Fujifilm cameras and their associated APS-C sensors (with an area of 366.6mm²):

• The X-T30 has 26MP, 6240×4160 photosites on its sensor. The photosite pitch is 3.74µm (dimensions), and the pixel density is 7.08 MP/cm².
• The X-T20 has a pixel count of 24.3MP, or 6058×4012 photosites with a photosite pitch is 3.9µm (dimensions), and a pixel density is 6.63 MP/cm².
• The X-T10 has a pixel count of 16.3MP, or 4962×3286 photosites with a photosite pitch is 4.76µm (dimensions), and a pixel density is 4.45 MP/cm².

The X-T30 has a higher sensor resolution than both the X-T20 and X-T10. The X-T20 has a higher sensor resolution than the X-T10. The sensor resolution of the X-T30 is 1.61 times as dense as that of the X-T10.

Sometimes different sensors have similar photosite sizes, and similar photosite densities. For example the Leica SL2 (2019), is full-frame 47.3MP sensor with a photosite area of 18.23 µm² and a density of 5.47 MP/cm². The antiquated Olympus PEN E-P1 (2009) is MFT 12MP sensor with a photosite area of 18.32 µm² and a density of 5.47 MP/cm².

“No matter what lens you use, no matter what the speed of the film is, no matter how you develop it, no matter how you print it, you cannot say more than you see”.

Thoreau quoted by Paul Strand, The Snapshot Aperture, 19(1), p.49 (1974)

Now that we have looked at the origin of 35mm film cameras, let’s turn our attention to full-frame sensors. A full-frame sensor is so named because the sensor is 24mm×36mm in size, equivalent in size to a film frame in a film camera. Why are we basing new technology on old concepts? Mostly for posterity’s sake, because why fix something that isn’t broken? The 24mm×36mm size first appeared in the early 20th century, and eventually became the standard film “frame size”. When the transition to digital occurred, keeping the image size the same meant that photographers could easily transition the use of legacy lenses onto digital bodies. The 35mm format became the reference format. Full frame is now the largest consumer sensor format before medium format (like the Fujifilm GFX100).

The size of a full-frame sensor has a significant impact on image quality. The large surface area means that more light can be gathered by the sensor, which is particularly beneficial in low-light conditions. The photosites often have a large pitch (more commonly referred to by manufacturers as the pixel pitch), it provides a broad dynamic range, and good low-light/high ISO performance. For example, the Leica SL2 (47.3MP) has a pixel pitch of 4.3μm, whereas the Olympus E-M1 (MII) with a MFT sensor has a pixel pitch of 3.32μm. When the area of a photosite is calculated, a photosite on the SL2 is 68% larger than one on the E-M1.

The downside of a full-frame sensor is that camera’s must be larger to accommodate the large sensor.Larger cameras mean heavier cameras.

Pixels actually help define image resolution. Image resolution is the level of visual detail in an image, and is usually represented as the number of pixels in an image. An image with a high density of pixels will have a higher resolution, providing both better definition, and more details. An image with low resolution will have less pixels and consequently less details and definition. Resolution is the difference between a 24MP image, and a 4MP image. Consider the example below which shows four different resolutions of the same image, shown as they would appear on a screen.

Each image is ¼ the size of the previous image, meaning it has 75% less detail. However it is hard to determine how much detail has been lost. In some cases the human visual system will compensate for details lost by filling in information. To understand how resolution impacts the quality of an image, it is best to look the images using the same image dimensions. This means zooming in the images with less resolution so they appear the same size as the 100% image.

You can clearly see that when the resolution of an image decreases, the finer details tend to get washed out. This is especially prevalent in regions of this image which have text. Low resolution essentially means details become pixelated or blobby. These examples are quite extreme of course. With the size of modern camera sensors, taking a 24MP (6000×4000) image, and reducing it 25% would still result in an image 1500×1000 pixels in size. The quality of these lower resolution images is actually perceived to be quite good, because of the limited resolution of screens. Below is an example of a high resolution image and the same image in low resolution at 1/8th the size.

They are perceptually quite similar. It is not until one enlarges a region that the degradation becomes clear. These artifacts are particularly prevalent in fine details, such as text.