Hypothetically could...

Gavjenks · Mar 6, 2014

It's not "deciding to move." You are FORCED to move. And no, not to recompose. You have to move to get (as close as possible to) the same composition you would have had. To maintain composition.

If I setup a FF and crop frame camera right next to each other, with the same lens pointed at the same target, at the safe aperture, and shot with both; then cropped the FF down to match the CF, you wouldn't see a difference in DoF.

This is correct. It's also totally irrelevant and unrealistic, because nobody changing cameras would actually stand in the same spot, since you'd get completely different images.
In actual practice, in the field, shooting real life, DOF is for all intents and purposes shallower for FF sensors, because you will always move exactly that corresponding amount to fill the frame with whatever image you want.

I think you're getting confused by referring to it as an "artistic" decision. It's not. No matter what artistic framing you decide on as a photographer, if I hand you a different format camera, you will instantly move your position to re-achieve that framing. No matter what your artistic choices are. Thus, it's not an artistic issue, because it applies equally to any and all artists with any and all visions. That makes it a technical issue.

JerryLove · Mar 6, 2014

I think we are just talking past each other. (want an example of where I wouldn't move an inch when changing crop factors? Landscape photography. Want another one? Panorama photography. Want another one? Lunar photography. Want another one?)

That said: I will ammend to say "building a FF sensor to CF size would be absolutely identical except for resolution and FoV"

Obviously: you can change the FoV by changing the focal length, which doesn't actually affect DoF (Understanding Depth of Field in Photography).

Gavjenks · Mar 6, 2014

Landscape photography.

Sure I would "move." Assuming you were operating at the edges of your focal length range amongst lenses you own and can't go any wider, you would indeed want to back up compared to the full frame. In reality, this wouldn't be an issue of "oh I hiked to position A and then some stranger handed me a new camera so I hiked to position B." It would be more like hiking to position B in the first place, because you know you need to be in a different place for your different camera ahead of time. The end result is still "moving" back with the crop camera for the same composition.

Panorama photography.

No you wouldn't move.

But you're not really helping your broader argument here. In fact, you just introduced a THIRD reason why the two sensors are practically different. Way more of a PITA to do panoramas. You'd have to take way more photos and do way more stitching and use up tons of extra time and probably get an inferior product from math errors. So now we have crop format, DOF (the majority of the time), and panorama difficulties.

Lunar photography

Unless you have a 1600mm lens or something, lunar photography never takes up the entire frame anyway, so this is irrelevant to the conversation. You're simply going to crop down to the small portion of the image in crop sensor or full frame that actually has the moon in it, so the sensor size is irrelevant, because you're cutting out the difference between the two.

Obviously, the difference in sensor sizes only matters to images that actually extend beyond the borders of the crop sensor size.....