Would Lumix FF 4:3 aspect do better?

Started 9 months ago | Questions thread
Joseph S Wisniewski Forum Pro • Posts: 34,157
Re: More like a particular diagonal

raminm wrote:

Joseph S Wisniewski wrote:

You're confusing cause and effect.

It just happens that the only currently manufactured 43.3mm diagonal sensors are in the 3:2 aspect.

You don't want a 4:3 aspect in a full DSLR, because a 4:3 43.3mm camera has a 26x34.6mm sensor, and that extra 2mm vertical adds another 3mm to the mirror and therefore to the backfocus (distance from rear lens element to sensor) so you end up with more complicated wide angle and normal lens designs, and louder, more vibration prone SLR mechanisms.

But on a mirrorless, those aren't factors any more, it's just as easy to make a 26x34.6 as a 24x36.

Not sure why you think there isn'y enough space within the current flange distance to implement the extra 2mm in the length of the mirror.

As BobNL already said, there are two entirely different things going on, the "registration distance" from the lens mount to the sensor, and the "back focus" from the rear lens element to the sensor. The registration distance can be practically anything from about 46mm to 39mm across Alpa, Canon, Minolta, Nikon, Pentax, all the SLR and DSLR makers of the last century.

The "back focus" converged to around 39mm for all camera makers, because of physics. To calculate back focus, just take the height of the image format (that's 24mm for 35mm "full frame", multiply by sqrt(2) because the mirror box is 24mm high and 24mm deep, because the focus screen at the top is horizontal, giving you 33.9mm. Then add 4mm for the thickness of a shutter mechanism, and depending on how much risk you were taking, 0.5mm to 1mm for how close you wanted the mirror to shave by the rear element, and viola! 39mm.

Now, if you kept the 43.3mm diagonal of full frame, and went to 4:3, your image would be 26x34.6mm, and the mirror would grown 2.8mm longer. Which doesn't sound like that much, until you realize...

  • energy increases with the 4th power of mirror height, so that little 8.26% increase in mirror length translates into a 37% increase in vibration and noise. Did you notice that the whole medium format SLR business has collapsed, and Blad and Fuji are only offering medium format mirrorless?
  • that you now have to make your normal lenses even more asymmetric. The shortest f1.4 fully symmetric lens you can make for an SLR with a 39mm back focus is 58mm. Nikon, Pentax, etc. tried this back in the late 50s, early 60s, and photographers said "that focal length sucks. It's 35% longer than our diagonal, all our images look flat and boring. Give us something shorter, more like what we had on rangefinders".  So, they computed asymmetrical 50mm lenses (which are typically 52mm when you actually measure them). 50mm is the half-way point, a compromise between the 43mm that photographers really want to shoot and the 58mm that lens makers really want to make. So, that extra 2.8mm means that the "optically good" lens jumps from 58mm to 62mm, while the "artistically good" lens stays at 43mm. So, you either move the compromise point out 2mm to 52mm, or make more difficult 50mm lenses with 41mm back focus.

Maybe you are right and I don't have a DSLR right now with me to verify this but  checking online, I see the Canon flange distance is 44mm for example. I think lack of flange distance is probably not a problem here and one must be able to redesign the mirror box to accommodate the extra 2mm in the mirror length without having to alter the optical system.

You are wrong. If you lengthen the mirror 2.8mm and your exiting lenses are already at the shortest backfocus that the camera maker thinks is safe to allow a mirror to approach, you have to redesign pretty much everything under 150mm. (even my Nikon 135mm has a rear element that's about at 39mm).

The biggest problem is the inherent ugliness of the 4:3 sensor for most general photography. TVs aren't running aspects of 1.72 (16:9) by coincidence, you know. The 4:3 aspect ratio is a throwback to the days when TVs used round CRTs to show an image, and programming was geared around a "two head dialogue".

Wrong, there is no inherent ugliness in the 4:3 aspect ratio.

I take it you've never had art history. Google "the golden ratio".

4:3 works well for a small, but profitable segment of the art world: head and torso portraits and face portraits. In painting, the painting time and paints required are proportional to the area of canvas. The amount of expensive picture frame required is proportional to the perimeter of the canvas. Profit is maximized when the image is square, but that's so visually objectionable that it is nearly unsellable. 4:3 is a nice compromise between ugliness and profit.

Aspect ratio is relative to the theme of the photo and composition but it is equally an artistic choice. One can take a head shot, or a landscape or else in a 4:3 aspect ratio or in a 16:9 aspect ratio or even in a panoramic aspect ratio, all personal artistic choices depending on what the artist wants to express or emphasize within the scene. None of the aspects ratios are inherently uglier or prettier than the other.

I could recommend a good book on art history.

As to regards to what made the TV manufacturers make the switch from the TV 4:3 standard to 16:9, this has little to do with photography.

True. It's the picture framing rationale, all over again. The round picture tube (and camera tube) is the most mechanically stable shape for a given weight of glass. The "flask" is an easy shape for glassblowers (I lead many lives).  Once you start trying to mask off edges, you find that wider aspects eat up your precious glass area too quickly.

Plus, 4:3 is a small integer Pythagorean triple, 3:4:5. That makes stage and camera relationships easy to calculate. Height =  60% of diagonal, width = 80%. The cameramen of the day learned to calculate that stuff in their heads.

One may speculate that in the contemporary cinema when the audience have very little interest in profound human interactions and in the complexity of human mind and in any attempt to decode or depict the deep aspects of human personality but instead, they mostly want to see scenes composed of super exciting actions, wide aspect ratios may inherently suit better this genre of cinema than aspect ratios closer to the square.

One may, but one would be wrong. The only "profound human interactions" that fit the 4:3 are the close 2 person head and torso dialogue. That's why so much early television serials, movies, and comedy looks like a bunch of interviews.

I still think there is more into this than I wrote above as I studied cinema for about 2 years or so.

Did you leave a zero off that?

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Rahon Klavanian 1912-2008.
Armenian genocide survivor, amazing cook, scrabble master, and loving grandmother. You will be missed.
Ciao! Joseph

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