DX and FX Sensor Aspect Ratio Rut - thinking outside the rectangle.

[eajames]

I've been thinking about how great it would be for Nikon to offer a DX body designed to capture an image with a different aspect ratio.

Using the limits of the DX lens line's image circle, the camera's sensor would be larger and more square. Personally, I favor a less

rectangular aspect ratio, like 5X7 or 3X4. Nikon could offer the same for their lens line covering the FX sensor - an FX body with a larger,

squarer sensor.

 

Why must 35mm film size and dimensions continue to influence Nikon dSLR design? Any thoughts?

[richard_driscoll]

Hi Eric,

 

I agree with you. I'd prefer an aspect ratio of, say, 1.33:1 or 1.25:1 since I find it a little hard to compose

pictures with 1.5 and easier with my ancient Zeiss folding camera which is 1.33.

 

Trouble is, so many people are used to 1.5 that they might be unhappy with something else. I guess that Nikon

would rather play safe since a wrong decision could cost them sales and they'd lose the investment in the sensor

manufacture.

 

Oh well - the loss of quality in cropping is pretty small really.

 

I remember reading that the very first Nikon 35 mm camera was 24 x 32 mm - an aspect ratio of 1.33. I don't

remember why they made it that way but the next one was 24 x 34 and then they went to 24 x 36. Perhaps their

collective memory remembers that!

 

Richard

[bjørn rørslett]

The initial decision to make 24x32 was an economic one, spurred by post-War economics in Japan. You got 40 frames on a 36 exp. film. The format proved unpopular for Americans shooting Kodachrome since it interfered with machine mounting of the slides. So Nikon slowly accepted the Western 24x36 standard and by 1954, no longer made their own format(s) [24x32, 24x34].

 

The height 24 mm is dictated by the lens flange-to-film distance ("register") and unless we want to buy a family of entirely new lenses, will not be changed. The image circle of FX/24x36 mm lenses is computed to cover slightly more than 43 mm. So the maximum width is 36 mm. You could have any aspect ratio of the frame as long as it fits within 24x36, for example, 24x24.

[lex_jenkins]

Absolutely! Not many folks are thinking outside the dictates of the 35mm SLR paradigm these days.

 

Unfortunately the 35mm format has devolved from a convenient, compact miniature format camera to facilitate handheld photography - revolutionizing photojournalism, documentary and travel photography in the process - until it has produced such rigidity in thinking that photographers are trying to force one format, one aspect ratio, to do everything.

 

In the process we've too often been forced to choose between large, bulky, heavy equipment for maximum potential image quality, and more compact equipment for convenience, with some sacrifices and compromises.

 

Just like always.

 

But the format size and aspect ratio are the same now.

 

Nowadays we have the equivalent to the Group f/64, who accept nothing less than maximum quality for everything, and wouldn't dream of using a camera without a tripod. We have those who embrace the miniature format for access to top notch super telephoto lenses for wildlife, sports and nature photography, where it excels, and forget the roots of the miniature format. There are still Pictorialists, or their contemporary equivalents. And many who prefer to use miniature format equipment as just that - small, compact, convenient, handheld.

 

So we see continual conflict between disparate types of photographers who all use the same equipment. Years ago, conflicts were fewer because these groups and disciplines used different types of equipment. Now we're all in the same virtual room, shaking our heads in bewilderment at each other's notions.

 

The best solution I can think of for now is to use a grid screen focusing screen to assist with previewing different types of compositions.

 

The next best solution would be to try to visualize how the cropped image will appear and compose accordingly.

 

Either way, you'll hear jeers from folks who disparage the notion of "throwing away" information. Nonsense. I never heard a single 6x7cm shooter claim with any credibility that 6x6cm or 645 was "throwing away" film.

[jonb]

I'll confess that I don't quite "get" this. I crop a high percentage of my shots. I often compose shots in the expectation that I'll be cropping them later. I've taken shots knowing that I will later crop them to a long "pano" format. Others I've known would end up being square. To me, one of the joys of the digital revolution is the ability to easily break out of the mental frame imposed by the physical frame of the camera.

 

When I was shooting slides, I had to concern myself with making the shot work in the 2:3 format because I had no practical alternative. That's no longer the case, and I found the transition easy and liberating.

 

I think Nikon should use sensors that are as large as practical, leaving it up to the photographer to decide what parts of the image space to "throw away." Bjorn explained the physical limitations that affect the sensor width (image circle size) and height (register) of F-mount bodies. With the D3 and D700, Nikon is now making bodies that fully exploit that space. How you choose to use that is up to you.

[nino]

I Think that this aspect alternative will happen eventually.

 

Just as film cameras matured over time, so will digital acquisition. Long term, when sensor production is cheap enough to experiment with, we may see companies like Nikon or Canon producing more specialist cameras, perhaps a consumer priced medium format, or panorama, the skys the limit really. And who knows what other ideas might come to fruition? As the photographic industry is relying more and more on software based image making, perhaps there will be some new system like consumer medium format (specifically for 6x6 or 645) that uses the new generation slr lenses and software interpolates the image onto a larger sensor? who knows

[Richard Williams]

Alternative aspect ratio crops are common in P&S cameras, either using a partial sensor area at the time of capture or (like the Canon G7/G9 optional 3:2 display) having on-screen indicators to show you what the crop would look like if you choose to apply it in post. And now of course we have the D3 with its 4:5 crop mode. So I'd say the answer is not to change the hardware, but to offer a range of capture modes and/or crop indicators in the viewfinder (how about using the on-demand gridline technology to provide crop frames of specific aspect ratios?).

[dan_brown4]

It never made sense to me that paper was 16x20, 11x14 & 8x10, while the film was 24x36. Personally, when I was shooting

film, I liked 6x7cm better than anything else.

[ellis_vener_photography]

The Nikon D3 , D700, and possibly ( I don't remember ) the D300 have a 1:1.25 ( 4x5 /8x10) aspect ratio internal crop option .

 

Also in the Develop module of Adobe Photoshop Lightroom, there are several pre-programmed crop options and you can create you own as well.

[ronald_moravec1]

It corresponds to the common 3.5x5 and 6x9 prints most people order. And these same people do not crop in photoshop.

 

Larger prints are different again so you crop the file or neg or get out your paper cutter.

 

To make things even more confusing, some P&S caneras are 4x5, some 4x6, and some offe 9x16.

 

I find the crop tool valuable. In CS3, I can set it to any ratio I want, then resize and move it all over the pic to get a final image. There are presets in it and I can add new ratios as the need arrises. Then if you deal with a decent lab, you are never suprised at the final result. Cheap consumer places still insist on further cropping what you send them.

[tachion]

It seems to me that Bjorn hits this one square on the head. We are stuck with the choice of lens to film (or digital

sensor) distance, because the mirror needs to flip up, and this dictates the maximum size of the sensor, which is FX.

Since the FX sensor can go all the way up to 24Mpixels, or perhaps even more with future sensors, for the FX format

this is not really a limitation.

 

DX is a little different. I noticed that the early DX cameras had an FX sized mirror flipping up, while the newer cameras

have a smaller mirror. In theory, that would allow a shorted distance of lens to sensor, but that would mean a whole new

line of specialized lenses, which just does not make sense.

 

You could conceive of a DX camera that has a sensor that is 24x24 instead of 16x24, but now you need the full sized

mirror again, you need the same prism as an FX camera, in other words, you may as well put in a 24x36 sensor, since

that will not drive the cost of the overall package. Who would buy a "D300++" with a 24x24 sensor if it is (hypothetically)

only $500 less than the full frame D700? Very few would want to save $500 for that limitation.

 

So it seems that given the limitations of the existing lens set, the FX and DX options are as good as it is going to get.

[ShunCheung]

Ellis, the D700 does not have the 4:5 mode.

 

My suggestion is always to capture the most amount of information when you press onto the shutter release button. You can always crop and throw out whatever you don't need later on during post processing. If you throw away information when you shoot, it is never recoverable.

[sandysocks]

I would like to see a 24x30 sensor with about 16mp in a vertical orientation camera that goes down to ISO 10. Fat chance, right?

[photo5]

Dan Brown said it right, there is a reason they call 6x7cm the "ideal format". It scales perfectly to an 8x10 inch print. The RB67 was an amazing camera, with a twist of the back you're shooting vertical and back again to horizontal. Wonderful! I also liked the square format, you're always shooting vert or horizontal all the time, just crop to the paper or better yet, throw convention out the window and print the square! 35mm format is a compromise, but certainly with the advent of wide-screen movies and now HD televisions, it is making a comeback. What I really hate with a passion is 16:9 format. THAT is just stupid, especially when you have to watch one of these films on your old Sony 27" lo-def TV at home!!

[richard_driscoll]

"In theory, that would allow a shorted distance of lens to sensor, but that would mean a whole new line of

specialized lenses, which just does not make sense."

 

That is almost exactly what Canon did with their EF-S lenses. The back focus is reduced and they can only be used

on the 1.6 crop cameras. This might mean that a DX-type crop mode won't be possible on the Canon full frame DSLRs.

 

By the way is there any theoretical reason why a body can't be designed to allow a picture height of say 26 mm

without needing an increase in back focus? It looks as if the Nikon F had a particularly large BF requirement

when it was designed; other SLRs at the time had a lesser requirement:

 

http://imaging.nikon.com/products/imaging/technology/history/rhnc06f-e/index.htm

 

There are no doubt design compromises - mirror size and associated cutoff for example.

[harvey_edelstein1]

Since you have to crop 3:2 to print size 8x10 the 5:4 ratio like on the D3 makes sense. This is easy way to compose realtime and save PP effort. Film users used to chose their favorite format, 6x7,645,6x6 or 35mm. I see this as a natural evolution of digital to allow us to choose our favorite format.

[eajames]

Very informative responses. Bjorn shoots down the idea with his explanation, and then the rest of you convince me that

the existing FX system is adequate for cropping all the way down to 24X24mm square - without hesitation.

 

Now if we could just get Nikon to light up the 1x1, 2X3, 5X7, and 6.5X8.5 frames in an FX viewfinder.

[eajames]

...3X4 that is...

[richard_driscoll]

Hi Eric,

 

If you crop the 24 x 36 frame you are throwing away pixels. If you use a different aspect ratio camera and don't crop then you aren't.

 

When I originally said the loss in quality was pretty small it was this loss I was referring to. For example, if you crop a 1.5:1 frame down to 1.25:1 the number of pixels being used goes down from (say) 12 M to 10 M and the linear resolution is less than it would have been with a camera designed for 1.25:1 also with 12 MP. That loss in linear resolution will only be about 10% however which is pretty small.

 

By the way, I'm not convinced that a 26 x 34.7 camera with a 43.4 mm image circle and a 1.33:1 aspect ratio can't be designed with the same back focus requirement as a 1959 Nikon F, but I'm sure this is all academic anyway!

[bjørn rørslett]

The answer is that it can't for obvious reasons. The mirror is supposed to be at 45 degrees, right? Then, if the frame height increases, the mirror has to be bigger, and hence the mirror box deeper. You can always have a smaller mirror in the same mirror box, but not a bigger than the chamber is dimensioned for. All hinges - literally - on the back-focus (register) distance that the lens system is designed to have. The register determines the depth of the mirror box.

[richard_driscoll]

Hello Bjorn,

 

You may well be right but you'll have to convince me that the size of the mirror in relation to the frame size is cast in stone.

 

When the Nikon F was designed there were other 35 mm cameras with different back focus requirements of which the Nikon was the largest - at least according to the Nikon reference I quoted above.

 

The size of the mirror and hence the back focus requirement surely depends on the acceptable degree of cut-off in the view finder - it is a trade-off. For example my old Pentax S1a shows cutoff with some long focus lenses because no doubt the mirror is a little small. It may be that the back focus requirement is less but I've not measured it.

 

Since the exit pupil positions of modern telephoto lenses may now be different from what it was in 1959 the design assumptions concerning mirror cutoff made then may not even be valid now anyway.

 

By the way surely register is the distance between lens mounting flange and image plane isn't it?

[bjørn rørslett]

Back focus = distance lens mounting flange to film plane = register.

 

Different makers made their systems based on different requirements, bu as soon as the register is defined, the optical parameters can't change. New lenses thus are computed based on the given parameter. For the 24x36 SLRS, the register range is Exacta with 41.5 to Nikon with 46.5 mm. The Nikon F was conceived with a very large mirror to minimise mirror cut-off with really long lenses. So they needed optics with a large register. F2, using a different method of hinging the mirror, had even bigger mirror and thus the 1200 mm f/11 lens had almost no cut-off.. With the D3, you do get more cut-off with lenses > 1000 mm but the impact is rarely problematic. The presence of electronic contacts inside the camera throat might limit the size of the mirror, I'll have to check my F2 against the D3 to clarify any difference.

[richard_driscoll]

Ah.

 

You certainly have not convinced me that the relationship between frame size and mirror size is cast in stone.

 

What's more re-engineering the mirror hinge arrangement is an additional design freedom.

 

By the way, I'm sure that:

 

Back focus = distance from film plane to rear lens element.

 

Register = distance from film plane to lens mounting flange.

 

They are rarely the same since most lenses intrude into the camera body.

[bjørn rørslett]

You may be right. The terminology in English is different from my native language. We'll concentrate on register

distance. Back focus will of course set limits to the mirror size and its positions during the travel up-down as

well.

 

Even with a special-hinged mirror the size is ultimately constrained by the depth of the mirror box. When the

mirror flips up, it has to go somewhere in its resting position. The arrangement is more to allow the height of

the mirror box be lowered towards the minimum size so the entire camera gets a lower profile. Plus,

counterweights are added to take up the mirror slap during the exposure.

[richard_driscoll]

Sorry - some lenses intrude ....