Cropping Percentages - DPChallenge Forums

Canon 12x IS USM (S3 IS built-in Lens) -- 36-432mm (35mm EQ)

12/22/2004 05:04:59 PM · #1

Okay.... So this might be a dumb question.

I have been looking at lens reviews and when they show a sample picture and say it is "100%" crop, do they mean it is the whole file the same size and aspect ratio as it came from the camera? If so, if I crop a picture less than the original how do I figure what percent it is?
Do I divide the total number of pixels in the smaller cropped version by the number of pixels in the original to arrive at a true percentage?

Thanks in advance.
Dick

GeneralE

Canon PowerShot S3 IS

12/22/2004 05:07:17 PM · #2

It should mean that all the original pixels are there, and there's been no resampling. It's typically an enlarged sample, since screen resolution is fixed at 72 dpi and the file (at least for print) is higher.

Message edited by author 2004-12-22 17:08:14.

Canon 12x IS USM (S3 IS built-in Lens) -- 36-432mm (35mm EQ)

12/22/2004 05:09:09 PM · #3

Thanks Paul, now what about how to figure my new percentage when I crop?

GeneralE

Canon PowerShot S3 IS

12/22/2004 05:15:02 PM · #4

I'm not sure what you're trying to do, or with which software ...

Oops -- gotta leave. I'll be back this evening : )

Message edited by author 2004-12-22 17:16:06.

kyebosh

Canon EF 80-200mm f/2.8L

12/22/2004 05:16:54 PM · #5

when they say 100% crop they mean they crop a small section of the picture and don't resize it so that you can see part of the entire photo at it's original size because the full photo would be very large. Hope that makes sense.

Canon EF 17-40mm f/4.0L USM

12/22/2004 05:20:56 PM · #6

I understand that too.

I guess what I really want to figure out is, how much of an original file is being used when I crop a section out to make a final image. Do any of you know what the formula is for that information.
Thanks

lebowski

Canon EOS-10D

12/22/2004 05:56:31 PM · #7

it depends on the resolution of the final image!
If you use Photoshop or similar software, just zoom to 100%, then crop a part of the image which can be fit in a window (for example a 500x500 pixel image)... that's a 100% crop :>

12/22/2004 06:07:11 PM · #8

Thanks again for the input.

I must go for awhile, but I am still confused.

Dick

kyebosh

Canon EF 24-70mm f/2.8L USM

Canon EF 80-200mm f/2.8L

12/22/2004 06:16:48 PM · #9

say I start with this image

and let's say that that was the full rez out of camera.

if I crop to here,

you'll notice that this portion of the crop is the same size as in the original. This is a 100% crop.

Bran-O-Rama

Canon EOS-5D

12/22/2004 06:32:53 PM · #10

Originally posted by autool:

I have been looking at lens reviews and when they show a sample picture and say it is "100%" crop, do they mean it is the whole file the same size and aspect ratio as it came from the camera?

No.

Originally posted by autool:

If so, if I crop a picture less than the original how do I figure what percent it is?

What do you mean crop a picture less than the original? Cropping will trim off the sides so no matter how you crop it, it will be less than the original.. unless you are talking about cropping an image that has already been downsized? And why are you trying to figure out the percentage?

100% crop means you are viewing the actual pixels of the image at full size, but just a portion of the entire image hence the crop.

Originally posted by autool:

Do I divide the total number of pixels in the smaller cropped version by the number of pixels in the original to arrive at a true percentage?

You are confusing the point. The total number of pixels in your crop has nothing to do with the percentage. Say my original file is 100x100 pixels. I could show a crop of 4x4px or 10x10px or 99x99px or 12x74px etc. etc. etc. As long as the cropped image hasn't been resized AFTER it has been cropped, it is a 100% crop. The dimensions of it are irrelevant.

Stepping out of the digital realm, take a photo printed on film or a page out of a magazine. Now get a pair of scissors and cut out a small piece. That piece you just cut out is a 100% crop of the "original", no matter how you slice it.

Your math equation is useful, only if your image is resized, not cropped, so the aspect ratio remains unchanged.

Message edited by author 2004-12-22 18:35:42.