Re: Pre-order: Fujifilm GFX 50S Medium Format body ($6,499)
Steve Spencer wrote:
I guess my point is that I don't think any one way of comparing across formats makes senses in a general way. I think you have to think of a particular use and then think about the most sensible way to compare for that use and what would be needed in it.
I'm not suggesting people should think a certain way - of course not, I'm suggesting websites present the comparison a certain way by default (I mean, they already do this, I just think they made the wrong choice for the default).
Steve Spencer wrote:
What is one person's "edge" use might be another person's primary use.
Of course there is no single right answer between f-number and entrance pupil invariance, but there is one answer which applies to more people than the other* - yet the more niche one is presented, often with no indication that this could be misleading.
*unless you want to argue that using the camera as a digital back on a view camera, or adapting lenses designed for a smaller format is going to apply to more people than using native lenses.
If you're using native lenses that at any given moment you are either DOF limited or you are not. If you are, then you can open the aperture more on the 35mm system and you end up capturing the same total light. If you are not DOF limited then you can also open the aperture more on the 35mm system because the native lenses go wider. This is a simplification but it applies to the vast majority of shooting scenarios.
alundeb wrote:
Actually DPR try to use about the same entrance pupil to get the same DOF and diffraction, that is the reason they use f/5.6 for FF36x24 and f/8 for 44x33 and get different shutter speeds
Yeah they almost do it right, but then change the shutter speed for no reason (yes I know the reason they do it - Richard Butler has claimed doing the comparison at the same total light is too hard to explain to people :doh.
alundeb wrote:
It is not easy to make one entrance pupil diameter work optimally for such a broad range of formats. f/2.8 on 1" and f/11 on MF would cause problems in both ends. f/2.8 on 1" would make it difficult to get sharp corners. f/11 on the XF 100 could be seen as limiting the full resolution.
Corners are already a major problem, case in point there is a lot more contrast in the 5DsR corners than the GFX. The solution is to only show the centre of the frame, that's more than enough to compare detail and noise, and centre performance is much more stable between lenses. The solution to the entrance pupil is to choose the best setting for the larger format and work your way down, when you reach the limit keep the shutter speed but increase the ISO setting after all the lack of an equivalent aperture setting is a deficiency of the smaller format. It's imperfect but it's in the spirit of making meaningful comparisons (again people generally choose settings according to the needs of the scene not according to the size of the sensor they are using).
Anyway I think I've made my point I'm not going to labour it any more, it's a criticism of gear websites rather than anyone here (all of whom are intelligent enough to make their own comparisons).
Mar 14, 2017 at 09:55 AM
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