Cropping and perspective correction

[john_g]

I've been wondering about this lately.

Partly provoked, I think, by criticism of new cameras that don't show 100% of the image in the viewfinder. I just don't get this. All I can assume is that it is important for people who never crop their images and need to know that what they saw is what will be printed. But who are these people? Photo journalists maybe, but who else?

Sure, none of us wants to waste pixels on unwanted rubbish around the edges of our pictures but my experience is that I always need that bit extra, either because I've not held the camera as square-on as I thought I was doing or because I decide to correct the slight convergence of verticals or horizontals that most pictures seem to end up with.

About which... I used to correct converging verticals only occasionally in the darkroom because it was such a faff. Now - and it might be just a phase I'm going through - I almost always adjust slightly converging/diverging lines to make them parallel, as my brain knows they are in reality. Do others do this? If so, why do you think it important? If not, why do you not do this?

And, on more-or-less the same subject, who cares whether the right format is 4:3 or 3:2? How many times does nature or circumstance give us the perfect picture that fits our frame exactly? I crop my pictures to include everything I think important and exclude everything that is extraneous. So how many end up with the original aspect ratio? Very few. It's no problem at all for on-line display but hell when it comes to framing prints. But would I compromise on this? No!

So I wonder how others think about all this and whether the practise follows the thinking.

[Monobod]

I often do correct converging verticals and I also crop my images to random sizes. I cut my own mounts and windows, always 500x400 overall, but the windows vary as needed. I also print virtually everything now at A3.

I must admit, I would like a 100% viewfinder though.

[john_g]

* Cropping
* Correcting verticals
* Windows vary as needed

Surely you've just described all the reasons why you don't need a 100% viewfinder?

[Roger_Provins]

I often do correct converging verticals and I also crop my images to random sizes ..... I must admit, I would like a 100% viewfinder though.

Agreed ... but as important to me is a decent size viewfinder. Just look through a good 35mm film SLR viewfinder or one of the new full-frame dSLRs to see what a big difference there is over the average APC sized finders.

[daft_biker]

I often do correct converging verticals and I also crop my images to random sizes ..... I must admit, I would like a 100% viewfinder though.

Agreed ... but as important to me is a decent size viewfinder. Just look through a good 35mm film SLR viewfinder or one of the new full-frame dSLRs to see what a big difference there is over the average APC sized finders.

Well if the average APS-C Canon these days is the 40D things are looking up on the viewfinder front I know what you mean tho....and agree!

I want a 100% viewfinder. I don't print and I think cropping to neaten up composition is the result of failure at the shooting stage. If I could see the edges of the frame I'd have less failures and spend less time editing on the computer (or at least have 1 less excuse for it!).

In macro DoF is closely linked to magnification so pics look wrong to me if heavily cropped. Cropping gives the impression of increased magnification without decreasing DoF and that doesn't happen in real life....unless you want to make pics from a SLR look like they were taken on a compact

I don't have a problem with converging verticals but if it bothered me I'd want a tilt and shift lens so I could get it right at the shooting stage complete with 100% view so no guessing as to how much extra space to allow when guessing how much correction will be needed so I can see the final composition in front of me instead of guessing how that's going to look after all my other guesses

[Roger_Provins]

Well if the average APS-C Canon these days is the 40D things are looking up on the viewfinder front I know what you mean tho....and agree!

I've just had a peep through my son's Canon 40D ... mmm ... well have a look through a Sony a900 when you get the chance

In macro DoF is closely linked to magnification so pics look wrong to me if heavily cropped. Cropping gives the impression of increased magnification without decreasing DoF ....

Surely only if you know the f stop used?

[daft_biker]

I've just had a peep through my son's Canon 40D ... mmm ... well have a look through a Sony a900 when you get the chance

Will do, if I get the chance. Is it nicer than the top end Canons that have had 100% finders for as long as I can remember? Bigger formats tend to have bigger viewfinders but as avarage APS-C viewfinders go the 40D is miles ahead of even the 30D before it...have never even held a Sony DSLR so I can't compare!

In macro DoF is closely linked to magnification so pics look wrong to me if heavily cropped. Cropping gives the impression of increased magnification without decreasing DoF ....

Surely only if you know the f stop used?

Not really as you can tell a big aperture from a small one by how quickly things go out of focus. If you're familiar with the size of the subject, the amount in focus together with the rate at which things go out of focus you can tell what's cropped heavily and what's not. Usually I can tell what's been through CombineZM and focus stacked too.....the results usually look computer generated.

And it's not that I never crop....I just don't like to

[beejaybee]

as avarage APS-C viewfinders go the 40D is miles ahead of even the 30D before it.

But it's still poor compared with the 5D.

There's no reason why it should be - either make the "hump" bigger, or get rid of the pop-up flash which "wastes" space which could be used for the viewfinder optics. If the must have an integral flash, perhaps it could "pop up" from somewhere else. Or use a different mirror configuration, like that trialled on the Olympus E-300 - OK, that wasn't a success, but there's no technical reason why this sort of design couldn't show a large, bright viewfinder image.

[LargeFormat]

The reason I bought a 4x5 was to get the verticals vertical. I used a shift lens on my 35mm to correct the verticals so it's no surprise that I correct the verticals in Paintshop Pro on digital. It certainly is a faff particularly as one needs to adjust the frame afterwards but I can't help myself.

By the way, can anyone explain why software adjustment always seems less saticfactory than a rising front or shift lens?

[daft_biker]

I agree and I also have a different gripe about the popup flash but I haven't checked cameras without them.....I can't mount the tripod ring for the MP-E upside down(tripod thread above the lens) unless I fit an extension tube so the ring clears the viewfinder prism.

Assuming no tube in place...
On a tripod with a centre column that can hang down low I'd have to use the camera upside down instead of just being able to rotate it on the ring....or if I wanted to mount a flash bracket (eg for a couple of 550's) on the ring I wouldn't be able to have the flashes mounted above the lens.

Off topic I know but you can add it to your list of reasons to dislike popup flashes

[Roger_Provins]

Is it nicer than the top end Canons that have had 100% finders for as long as I can remember?

I wouldn't like to say it's better as I've never had the good fortune to use a full-frame Canon - but the Sony a900 viewfinder is big, bright and beautiful (oh, and it doesn't have a pop-up flash!)

... you can tell a big aperture from a small one by how quickly things go out of focus. If you're familiar with the size of the subject, the amount in focus together with the rate at which things go out of focus you can tell what's cropped heavily and what's not.

... well I don't think I could

[Chris Cool]

I think cropping to neaten up composition is the result of failure at the shooting stage.

Oh! Oh, I'm in trouble

[Roger_Provins]

I think cropping to neaten up composition is the result of failure at the shooting stage.

Oh! Oh, I'm in trouble

me too!

... but I don't agree ... shots can be taken with cropping in mind as anyone coming from TLRs and 6x6 film will know.

[Monobod]

John, whilst I do crop my images to obtian, for instance, a letterbox view, I do not crop every image. It is for that reason that I would love a full frame viewfinder. It is annoying to compose an image and then get back home to find that an object not wanted on the edge of the image has been recorded, even if one has tried to reposition to avoid it.

Also if one has to crop and then resize the image back to A3, some resolution is lost. With the K10D/GX10 at 10Mp, printing to A3 at 300dpi is not possible, so everything that reduces this further is a pain.

Perhaps things are better with the k20D, as it has better resolution to start with. One reason to upgrade one day, I suppose.

[daft_biker]

I think cropping to neaten up composition is the result of failure at the shooting stage.

Oh! Oh, I'm in trouble

me too!

... but I don't agree ... shots can be taken with cropping in mind as anyone coming from TLRs and 6x6 film will know.

It's hardly a serious crime....unless you want your pics to be an accurate record to a known scale. Life is much easier not to crop then.

Anyway, here's a crop of mine


Cropped from this shot:

(5:1 on APS-C)

Who knows what I was thinking with the weird angle and I couldn't have been thinking about the antenna poking out of frame. I also think it illustrates how much cropping can make the DoF look wrong in this type of shot.

A failed shot? In some ways I think so but it was taken after a discussion MickLL started on here about how compound eyes could look soft at some viewing resolutions.

[daft_biker]

And FWIW the tripod ring doesn't hit the prism bump on my EOS 3 without built in flash....one more reason not to like popup flashes

[Chris Cool]

I think cropping to neaten up composition is the result of failure at the shooting stage.

Oh! Oh, I'm in trouble

me too!

... but I don't agree ... shots can be taken with cropping in mind as anyone coming from TLRs and 6x6 film will know.

It's hardly a serious crime....

Ah, I can sleep easy in my bed

[Malcolm_Stewart]

...Is it nicer than the top end Canons that have had 100% finders for as long as I can remember? Bigger formats tend to have bigger viewfinders but as average APS-C viewfinders go the 40D is miles ahead of even the 30D before it...

I'm beginning to wonder if my wearing bifocal specs for the last 30 years (since my Minolta SRT101 days) has made me less worried about this aspect - perhaps I now never get the full benefits of a good viewfinder. In the last few days I've done lots of shooting moving amongst 5D, 1D MkIII and 30D bodies, and I just got on with it, using the appropriate body for what I was shooting. When I needed flash I used a 220EX on an extension lead with my 30D.

{Reminder to self - better check how good my Dynax 7 viewfinder is, and my old T90, & F3 +/-HP!}

[Terrywoodenpic]

After converting from raw I always...

Remove Pincushion/ barrel distortion with PT lens
Correct verticals before doing any other manipulations such as minor tweaking of curves and dodging and burning etc.

However it is very rare that I crop... certainly less than 1 in 50.

The 40D seems to have the same view allowance as my previous film cameras, and I always seem to get what I expected to be in final image.

[Terrywoodenpic]

I think cropping to neaten up composition is the result of failure at the shooting stage.

Oh! Oh, I'm in trouble

me too!

... but I don't agree ... shots can be taken with cropping in mind as anyone coming from TLRs and 6x6 film will know.

It's hardly a serious crime....

Ah, I can sleep easy in my bed

Quite so..... I always painted in the corners of my Rolleis to give alternative 5x4 views. I almost never composed as a square.