You should know that in photography, 6x6 doesnt equal 6x6cm image area, neither is 645 the same as 6x4,5cm nor is 4x5" 4x5", it would just have been too easy. Except for 135 film (small frame) the sizes include the borders of the roll film, making a 6x6 lens have to produce a circle of good quality that can fit a square of around 55x55mm. It varies a lot though. For example, im pretty sure my 6x6 P6 produces a smaller picture area than my 645 fujis do and my 6x12 produces only around 10cm wide a picture.
For large format it gets even more complicated. First we have to take into account that the nominal sizes are those of the film holders rather than the film itself. The film sheet has to be i bit smaller to fit the holder. By chance, this makes the slightly larger 13x18cm format have exactly 5" wide sheets, while film called 5x7" is slightly narrower than 5". In addition to this, there are the borders. For 4x5" format in total that means the image area is about 95x120mm which is between 0.5 to 1 cm smaller in each direction than the name suggests.
Does this affect digital as well? In a way, it does. Making a 60x45mm or a 60x60mm mf back wouldnt make anyone happy except the lens manufacturers. A lot of lenses for regular 6x6 or 645 systems would be quite useless with such a back since the corner would lose light, image qualitey or both. However, on digital backs and cameras, if you look carefully you will find the actual size mentioned. Just remember that while 44x33 is a 645 crop, around 55x55 is a perfectly sized 6x6 sensor.
Does this affect digital as well? In a way, it does. Making a 60x45mm or a 60x60mm mf back wouldnt make anyone happy except the lens manufacturers. A lot of lenses for regular 6x6 or 645 systems would be quite useless with such a back since the corner would lose light, image qualitey or both. However, on digital backs and cameras, if you look carefully you will find the actual size mentioned. Just remember that while 44x33 is a 645 crop, around 55x55 is a perfectly sized 6x6 sensor.
On top of that, there are so many misconceptions on how film/sensor size affects the photos floating around the internet. I tried to straighten them out during a rainy day this winter.
I should try to make a shorter and better version of this, i know. But it at least tells how it sorts the myths out from the facts if you can get yourself through it.
Thats all for today, or tonights darkroom class will be a teacher short.
Thats all for today, or tonights darkroom class will be a teacher short.
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