Cropping & Pixels

Tom Potter

RE: Cropping & Pixels

Hey All,

A bit unclear about something. I saw a video today where in it was explained that "you can crop this image, but, you do so at the risk of tossing out a lot of pixels."

Here is what I am not clear on. I fully understand that a lot of pixels (info) would be tossed out. However, when you crop an image, you are cropping out an undesired portion of the image. Say, for instance, you crop out as much as 1/3 of the original image. So then, you are left with, the tree you wanted, let's say, and cropped out a good portion of sky that did not add anything to the image. I can see that you are now not able to blow up the image as much as you would have been able to, had you not cropped off 1/3 of the original image. Do you suppose THAT was what the video was referring to??

Thanks....

Gary752

Sounds like they were talking about cropping a .jpg file. What they are saying is that once you crop the file and save it, you can never get those pixels back, where it is the opposite with a RAW file.

GaryB

kdog

Tom Potter wrote: »

RE: Cropping & Pixels

Hey All,

A bit unclear about something. I saw a video today where in it was explained that "you can crop this image, but, you do so at the risk of tossing out a lot of pixels."

Here is what I am not clear on. I fully understand that a lot of pixels (info) would be tossed out. However, when you crop an image, you are cropping out an undesired portion of the image. Say, for instance, you crop out as much as 1/3 of the original image. So then, you are left with, the tree you wanted, let's say, and cropped out a good portion of sky that did not add anything to the image. I can see that you are now not able to blow up the image as much as you would have been able to, had you not cropped off 1/3 of the original image. Do you suppose THAT was what the video was referring to??

Thanks....

Your interpretation is probably what they meant from the sounds of it. It's correct anyway.

arodney

You can non destructively crop in Photoshop if you setup the paramaters correctly. The pixels are not discarded, only 'hidden'. Turn OFF Delete Cropped Pixels.

TonyCooper

I think the point is that if you crop an image, you have fewer pixels
within the remaining area than were in the original photograph. This means
that what remains may be a degraded image if the crop is severe.

I can't imagine a 1/3rd crop presenting a problem with the average file
of a DSLR image, though.

I don't see how cropping in LR or cropping in PS without discarding
the cropped pixels affects the remaining cropped image at all. Those pixels
in the area cropped out don't magically move into the area the
image is cropped to.

Cropping in LR or PS without discarding cropped pixels only allows
you to start over with the original sized image.

But what do I know?

Tom Potter

Thank you all for your input

Hey Tony - Please see my comments immediately following each of your comments in red....

TonyCooper wrote: »

I think the point is that if you crop an image, you have fewer pixels
within the remaining area than were in the original photograph. This means
that what remains may be a degraded image if the crop is severe. Not sure I follow what you're saying. Wouldn't the only issue be that the remaining portion of the image can now not be printed at as large a size, as opposed to if I had not cropped the image at all? I can see how "....what remains may be a degraded image....", but, only if I print that smaller-than-the-original-image at a size that would would cause the image to be degraded.

I can't imagine a 1/3rd crop presenting a problem with the average file
of a DSLR image, though.

I don't see how cropping in LR or cropping in PS without discarding
the cropped pixels affects the remaining cropped image at all. Those pixels
in the area cropped out don't magically move into the area the
image is cropped to. How do you not discard cropped pixels. Isn't cropping an
image, in essence, discarding pixels??

Cropping in LR or PS without discarding cropped pixels only allows
you to start over with the original sized image.

But what do I know?

TonyCooper

Tom Potter wrote: »

Thank you all for your input

Hey Tony - Please see my comments immediately following each of your comments in red....

WOW...that red type burns the eyeballs!

[quote} Not sure I follow what you're saying. Wouldn't the only issue be that the remaining portion of the image can now not be printed at as large a size, as opposed to if I had not cropped the image at all? I can see how "....what remains may be a degraded image....", but, only if I print that smaller-than-the-original-image at a size that would would cause the image to be degraded. [/quote]

Sorta, if I follow you. A severe crop to a small portion of the original image would
not be degraded if you printed it as a very small image. But, we don't do that.
What we do do is crop to what we want in the image and print that in one of the
normal print sizes. You might crop to a postage stamp size of your image, but
you aren't going to print it at that size. Print it at 4" x 6" and it may be degraded
beyond use.

How do you not discard cropped pixels. Isn't cropping an
image, in essence, discarding pixels??

Lightroom is non-destructive. Cropping in LR just removes the pixels from
outside of the cropped area from view. You can undo that crop and re-crop
to a larger size because the pixels are still there. Any edits in LR can be
undone.

If you open a RAW file in PS, and crop it, it will open as the cropped
image. However, if you open that same RAW file again, you can re-crop
it differently because the pixels outside of the cropped area are not
lost.

If you crop in PS with "delete cropped pixels" unchecked, you don't lose
the original image if you go to crop again.

puzzledpaul

// Not sure I follow what you're saying. Wouldn't the only issue be that the remaining portion of the image can now not be printed at as large a size, as opposed to if I had not cropped the image at all? I can see how "....what remains may be a degraded image....", but, only if I print that smaller-than-the-original-image at a size that would would cause the image to be degraded //

Imo, this is spot on ... what the user decides to do with the remaining portion is another matter ... trying to print (this remaining portion / area) to the original size - at the original resolution - means something's got be tweaked / compromises made.

This topic is also sniffing around the edges of something else that I find intriguing ... how 'crops' are referenced.

Here, it's been implied that after the crop, the remaining portion is the same aspect ratio as the original file (yes, I know it doesn't have to be) ... so what exactly does a 30% or 1/3 crop mean?

30% of the area (pixels) of the original file have been discarded, leaving 70%
or
The crop position - along both axes - is 30% along both H and V edges - leaving a file that has had 51% of the pixels discarded.

Sometimes, it gets even more complicated (imo) when things are written in an ambiguous manner, such that the reader is unsure whether 30% (say) has been removed ... or is the remaining portion

Re non-destructive 'cropping', Canon's own DPP also allows this, when converting raws to the chosen format ... I assume Nikon users have access to similar s/w ... for those non LR users?

pp

TonyCooper

puzzledpaul wrote: »

//
This topic is also sniffing around the edges of something else that I find intriguing ... how 'crops' are referenced.

Here, it's been implied that after the crop, the remaining portion is the same aspect ratio as the original file (yes, I know it doesn't have to be) ... so what exactly does a 30% or 1/3 crop mean?

30% of the area (pixels) of the original file have been discarded, leaving 70%
or
The crop position - along both axes - is 30% along both H and V edges - leaving a file that has had 51% of the pixels discarded.

I would take it to mean what remains after the crop is 2/3rds of the original
photo. The part removed could be any contingent space (horizontal or vertical band
or L-shaped area) that the photographer did not consider to be essential to the photograph.

I suppose a "one-third crop" is an ambiguous term since the third can be
either taken out or what remains.

(Rounding a 30% crop to a 33 1/13 percent or one third crop)

Re non-destructive 'cropping', Canon's own DPP also allows this, when converting raws to the chosen format ... I assume Nikon users have access to similar s/w ... for those non LR users? [/quote

Nikon offers Capture NX2, which is non-destructive, but I use either Lightroom or
Photoshop to process my Nikon-produced RAW files. Both can be non-destructive
of RAW files.

kdog

TonyCooper wrote: »

Nikon offers Capture NX2, which is non-destructive, but I use either Lightroom or
Photoshop to process my Nikon-produced RAW files. Both can be non-destructive
of RAW files.

Actually, I don't think it's possible to destructively edit a raw file with any of the mainstream tools out there. Certainly none of the Adobe products support it. I'm pretty sure raw is always considered a read-only format. Although I welcome any data to the contrary.

Tom Potter

kdog wrote: »

Actually, I don't think it's possible to destructively edit a raw file with any of the mainstream tools out there. Certainly none of the Adobe products support it. I'm pretty sure raw is always considered a read-only format. Although I welcome any data to the contrary.

Thank you all for the great input. I agree, RAW is a non-destructive process.

JasonMorrowPhoto

Tom Potter wrote: »

Thank you all for the great input. I agree, RAW is a non-destructive process.

arodney wrote: »

You can non destructively crop in Photoshop if you setup the paramaters correctly. The pixels are not discarded, only 'hidden'. Turn OFF Delete Cropped Pixels.

Where do you turn off Delete Cropped Pixels? I cannot find it. I have Photoshop CS6 Thank you:D

OffTopic

When you activate the crop tool in CS6, on the toolbar at the top there is a check box labeled "Delete Cropped Pixels". Uncheck the box.