[audiobomber]

So your dismissal of equivalence is that it isn't accurate to three decimal places? Has it occurred to you that the FA 50mm f1.4 has a focal length of 53mm? That the DA 60-250mm is only about 135mm at close focus and maximum range? That an f2.8 lens can have a T-stop of f3.3? Or that f8 is not precisely f8 (f5.6 x 1.4 = 7.84)? That f/1.2 may be used in either a half-stop or a one-third-stop system? You can't see a difference of 400 pixels in 12 million. Your eye can't tell the difference between 1.5x crop or 1.53X crop. Photography is nowhere near as precise as mathematics because it is also subjective.

Have a play with a DOF calculator. It will show that you can equalize DOF between formats, but DOF is not a precise measure, so don't be expecting mathematical precision. A Flexible Depth of Field Calculator

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Last edited by audiobomber; 01-12-2016 at 04:46 AM.

[osv]

Using the 32.573mm lens, as it gives me a subject (1.7m person) height of 75% (3,003px) of the frame (height in landscape orientation) using the K-3 when taken from a distance of 4.720m, and, an aperture of f1.4, the portion of the picture that is in focus is from 4.245m to 5.315m, so my depth of field is 1.070m.

it's not that precise.

there is no such thing as a universal calibration standard for lens measurements, so a nikon 50mm lens could easily be a couple of mm longer than a canon 50mm lens... same thing with aperture, it's only whatever arbitrary measurement the manufacturer assigns the lens... it'll generally be pretty close with modern lenses, but nowhere near as precise as you are calculating.

take for example the batis 25mm prime, it's actually a ~22-23mm prime... some people speculate that modern lenses might be wider in order to leave elbow room for in-camera distortion correction.

another example would be the olympus 24/2.8 legacy prime, it's the widest 24mm prime that i've ever put on the a7r, probably by ~2mm or so.

[BigMackCam]

To answer the OP's question, to my knowledge it is not possible to emulate a picture taken using a 35mm ('Full Frame') sensor using a camera that does not have a 35mm sensor, i.e. an APS-c size sensor.
..
Also, Crop Factors and 35mm Equivalent values serve ONLY as a visualisation tool to help us see with that camera and lens combination.
...
Apologies for the very long post.

Thank you for taking the time to give such a comprehensive reply - this really is helpful

What I draw from your post, along with the rest of the information I have at hand is that, while it may be difficult - perhaps impossible - to *precisely* emulate a specific combination of camera sensor, lens and settings with an alternative format sensor and lens, it *is* in fact possible to closely *approximate* it. Yes, field of view may be just very slightly out; depth of field may be just a little different; rendering characteristics will affect overall rendering to a greater or lesser extent; sensor or film performance will vary in terms of exposure, dynamic range and noise / grain. But, it is certainly possible to achieve a good approximation.

[AutoGOD]

Thank you for taking the time to give such a comprehensive reply - this really is helpful

The pleasure is mine. You've got it you can get close, even imperceptibly close, but you'll never get total precision.

[dtmateojr]

It hasn't been mentioned in this thread, but equivalence theory requires sensors of similar generation and technology.

Like film?
Film debunks equivalence though

[audiobomber]

Like film?
Film debunks equivalence though

No, it doesn't. The DOF calculator linked above works for film and digital. You will have equivalent images if you shoot 35mm film @ f/5.6, 100mm, 1/150s, ASA 400 as you will with 110 film @ f2.8, 50mm, 1/150s and ASA 100 film. Same DOF, same FOV, similar grain, same perspective. You can also translate that to the larger film formats as long as you calculate crop factors vs. FF.

[BigMackCam]

No, it doesn't. The DOF calculator linked above works for film and digital. You will have equivalent images if you shoot 35mm film @ f/5.6, 100mm, 1/150s, ASA 400 as you will with 110 film @ f2.8, 50mm, 1/150s and ASA 100 film. Same DOF, same FOV, similar grain, same perspective. You can also translate that to the larger film formats as long as you calculate crop factors vs. FF.

That's my understanding, too. The only thing I would add is that each film will obviously lend a certain character to the colour, contrast and grain, as well as a good degree (in most cases) of exposure lattitude... but equivalence in terms of field of view & depth of field shouldn't be any different from a FF digital sensor, right?

[UncleVanya]

Film is actually a great option for looking at equivalence because the underlying "pixels" are set by the film and "sensors" of varying sizes are all assumed to have the same lineage and characteristics if they are the same film. Not entirely sure if Kodak or another manufacturer ever took liberties with that assumption and packaged slightly different emulsions in varying sizes with the same labeled film type and speed but I suppose it could have happened.

In film you don't end up looking across generations or technologies - you have a more level playing field in theory from which to examine the question.

[dtmateojr]

No, it doesn't. The DOF calculator linked above works for film and digital. You will have equivalent images if you shoot 35mm film @ f/5.6, 100mm, 1/150s, ASA 400 as you will with 110 film @ f2.8, 50mm, 1/150s and ASA 100 film. Same DOF, same FOV, similar grain, same perspective. You can also translate that to the larger film formats as long as you calculate crop factors vs. FF.

In your example your are using different film emulsions. 400 and 100. How are they equivalent? Use same emulsion but different formats, say, 8x10 velvia 50 and 135 velvia 50. Same grain, same exposure.

---------- Post added 01-13-16 at 08:16 ----------

Film is actually a great option for looking at equivalence because the underlying "pixels" are set by the film and "sensors" of varying sizes are all assumed to have the same lineage and characteristics if they are the same film. Not entirely sure if Kodak or another manufacturer ever took liberties with that assumption and packaged slightly different emulsions in varying sizes with the same labeled film type and speed but I suppose it could have happened.

In film you don't end up looking across generations or technologies - you have a more level playing field in theory from which to examine the question.

Correct. Same emulsion means same film regardless of size. 8x10 velvia is exposed exactly like 135 velvia. Same grain (noise), same brightness. Size doesn't matter.

[BrianR]

This means that depth of field is not related sensor size, and reinforces our belief that a 50mm lens is, in fact, a 50mm lens.

You might want to state the assumptions you've used in your DoF calculations (specifically, what's happening to your circle of confusion as you vary formats and the implications this has in a real world print comparison).


Anyway, the 'derivations' that show you'll get the same DoF under some equivalence conditions use simplified equations for DoF. Ones that are pretty true when the subject distance is large enough compared to the focal length. In other words, it's close enough for most people at everyday distances, but not a mathematical gospel.

[BigMackCam]

Size doesn't matter.

Over the years, how I've wished this were true...

[dtmateojr]

Over the years, how I've wished this were true...

It is true. The optimal size for humans is 8x10 viewed from about 1 ft. It means I can print a 2Mp image at billboard sizes since people would be viewing it from hundreds of meters away to the apparent size of 8x10.

[BrianR]

Size doesn't matter.

Over the years, how I've wished this were true...

It is true. The optimal size for humans is 8x10 viewed from about 1 ft....

Ohh man, I'm feeling inadequate now

[BigMackCam]

It is true. The optimal size for humans is 8x10 viewed from about 1 ft. It means I can print a 2Mp image at billboard sizes since people would be viewing it from hundreds of meters away to the apparent size of 8x10.

I think you missed the joke, there

8x10 would be nice, though, no doubt about it...

[dtmateojr]

I think you missed the joke, there

8x10 would be nice, though, no doubt about it...

Ok. ROFL!!!