Questions regarding perspective correction in PP: Last night a very knowledgeable photographer addressed my photo club and, among other things, stressed the importance of doing...

jackm1943 Loc: Omaha, Nebraska

Last night a very knowledgeable photographer addressed my photo club and, among other things, stressed the importance of doing perspective correction in the camera rather than PP. He stated that no PP programs, including Photoshop, do it without some loss in sharpness or accuracy in the areas most affected. I have seen this but only when trying to make some extreme corrections. But I suppose if it's noticeable when doing extreme corrections, there may be less noticeable losses when making less extreme corrections.

I'm curious (1) if others have noticed this, and (2) what is going on at a pixel level when this happens.

dirtpusher Loc: tulsa oklahoma

even ansel adams did pp on some his.

jackm1943 Loc: Omaha, Nebraska

dirtpusher wrote:

even ansel adams did pp on some his.

You're correct dirtpusher, but ansel would have done any perspective correction in the camera, either by shifting the lens on his view camera, or by tilting the enlarger easel for medium format. He didn't have Photoshop of course, but I suspect he would have been a big fan if alive today.
JackM

dirtpusher Loc: tulsa oklahoma

jackm1943 wrote:

You're correct dirtpusher, but ansel would have done any perspective correction in the camera, either by shifting the lens on his view camera, or by tilting the enlarger easel for medium format. He didn't have Photoshop of course, but I suspect he would have been a big fan if alive today.
JackM

all the above :thumbup:

lighthouse Loc: No Fixed Abode

jackm1943 wrote:

Last night a very knowledgeable photographer addre... (show quote)

How did that "very knowledgeable photographer" propose that it should be done "in camera"?
If he meant by lens shifting then thats out of the bounds of most people.
If he meant "in camera software", I don't see any difference in doing that "in camera", and doing it in PP.

Kristoes

lighthouse wrote:

How did that "very knowledgeable photographer" propose that it should be done "in camera"?
If he meant by lens shifting then thats out of the bounds of most people.
If he meant "in camera software", I don't see any difference in doing that "in camera", and doing it in PP.

I echo your questions, and look forward to the responses.

jackm1943 Loc: Omaha, Nebraska

lighthouse wrote:

How did that "very knowledgeable photographer" propose that it should be done "in camera"?
If he meant by lens shifting then thats out of the bounds of most people.
If he meant "in camera software", I don't see any difference in doing that "in camera", and doing it in PP.

Hi lighthouse. There's only really two ways with fixed lens cameras such as DSLRs. One is to use tilt-shift lenses, the other is to just make certain the camera is level, not pointing up or down. That's easier said than done, and sometimes just not possible. And tilt-shift lenses are pretty low on my priority list.

I have no problem with leaving some perspective issues uncorrected because it looks more realistic to me. Having a large format background tho, sometimes I do like to fully correct perspective in PP and have noticed problems only when trying to make severe perspective corrections.

SharpShooter Loc: NorCal

Jack, your speaker is correct, but that also applies to exposure, noise, sharpness etc., etc.
But Lighthouse is also right. Was the speaker ad go aging that we all go out and buy a TS lens? They aren't good for much else, since a 2.8 is a rockets hip, and ALL are manual.
If you are doing professional architecture, you either have a set of TS lenses or you're using a view camera.
I've even consulidered one of the cheap Russian TS lenses, sinsemilla they pop up used once in a while very inexpensively.
Its true, any interpolation at the pixel level, is purely an educated guess by the PP program, but good enough for anyone not shooting professionally.
So your speaker would be correct, put not really very practical for most. ;-)
SS

jackm1943 Loc: Omaha, Nebraska

SharpShooter wrote:

Jack, your speaker is correct, but that also appli... (show quote)

Hi SharpShooter, You're right of course, but for us he was recommending keeping the cameras level. He understands that most of us amateurs will not purchase tilt-shift lenses (unless we get a really good deal on one of course). :D

lighthouse Loc: No Fixed Abode

jackm1943 wrote:

Hi SharpShooter, You're right of course, but for us he was recommending keeping the cameras level. He understands that most of us amateurs will not purchase tilt-shift lenses (unless we get a really good deal on one of course). :D

Ahhhh and that brings up a different problem that has exactly the same result that he was trying to advocate against.

To keep it level, the top of the building is now not in the photo, so you have to put on a wider lens to get the top of the building in, and then crop the photo to frame your photo how you set up your composition in the first place, thereby minimising the pixels used.
So this will impact on the final image IQ as well, maybe moreso than software perspective correction of the image would have.

So I think it might be one of those cases where he was specifically right, but generally barking up the wrong tree.

I am not saying that we shouldn't be aware of the issue he was raising.
Just that, in practice, maybe it really wouldn't matter enough to worry about.

jackm1943 Loc: Omaha, Nebraska

lighthouse wrote:

Ahhhh and that brings up a different problem that ... (show quote)

But the problem is that it does matter, at least when one is trying to correct severe perspective distortion. The most corrected parts get sort of smeared around, so there appears to be a limit on just how much correction one can make, and that's what I'm trying to find if anyone knows the limit or just what is happening. Perhaps the only practical solution is just to not try to fully correct all perspective distortion?

SonyA580 Loc: FL in the winter & MN in the summer

Getting it right in the camera is not always possible. I'm a stickler for vertical lines being vertical and, correcting perspective in PhotoShop (7.0) doesn't, as far as I can tell, cause any "loss of sharpness". I'd like to hear others opinions.

jackm1943 Loc: Omaha, Nebraska

SonyA580 wrote:

Getting it right in the camera is not always possible. I'm a stickler for vertical lines being vertical and, correcting perspective in PhotoShop (7.0) doesn't, as far as I can tell, cause any "loss of sharpness". I'd like to hear others opinions.

Hi SonyA580. I know that you can get some smearing in the corners when trying make severe perspective corrections, but I've not noticed any losses when making minor or moderate perspective corrections.
JackM

Pablo8 Loc: Nottingham UK.

I have used (still got) 5x4 Sinar for a number of years, so in camera corrections were the order of the day. However, my Nikon armoury only includes one shift lens, so some corrections have to be done pp. Usually this has not been a problem to achieve the finished print looking good. Photoshop does what I ask of it, perhaps because I know what, and how to ask.

DanRobinson Loc: Charlotte, NC

i think it was here on UHH.

Someone took a lens from an obsolete camera removed all the hardware from the back, super-glued all the sharp metal and screw holes, and made himself a perfectly usable tilt shift lens.

He hand-held the lens against a digital camera body and had at it.

Worked out pretty good.

I hesitate to expose the innards to bumping and extra dust, but it would not be hard to make a bellows and a holder to take care of the light-leak and lens shaking.

Come to think of it, there's a lens to an old film camera in one of these boxes here . . .