Crop size


ARI 17 567 United Kingdom
6 Sep 2020 4:23PM
I use the image editor within Gogle Chrome to do quick edits for any picture that need to submit. Normally the instruction is the pixel count for the longest size. I have come across referances to percentage crop. How is this done? Picture attached is a tiny crop of a 68mp raw file taken with a 5DsR, how do I work out if it is a 200, 300, 400 percent or whatever crop. Slight editing to enhance the sinister, do not mess with me look.
Thanks.6761_1599405646.jpg
6 Sep 2020 4:58PM
You would need to know the pixel size of the original and the pixel size of this image. The original I would assume is 100 percent no matter how many pixels there are. So any crop from the original must be a percentage but you can't work that out without knowing the number of pixels unless it is a hard copy printed at its original size then you could measure it in mms/ins and work it out from there, but you have to have a starting measurement.
ARI 17 567 United Kingdom
6 Sep 2020 10:12PM
Pixel size from exif data of original un worked image is 8688 x 5792. File size is 61 MB.
Cropped image size is 1313 x 875. File size is 258.4 KB.
So, how is the crop factor worked out?
Jestertheclown 11 8.3k 253 England
6 Sep 2020 10:35PM
The dimensions of the original are irrelevant.
A crop defined by percentage, is just that.
If you crop an image by let's say, 75%, then 25% will be uniformly removed from the image's edges, retaining the original aspect ratio.
That will always be the case, regardless of the physical size of the original.
It's easier to understand if you can see it.

Try this, it's a bit long in the tooth but still relevant.

Jestertheclown 11 8.3k 253 England
6 Sep 2020 10:52PM
Re. the above; I could recall vaguely having used an editor that allowed cropping via percentage and I've found it.
If you want to have a go yourself, FastStone offers percentages as a method of sizing your crop.

(I also discovered that Affinity expects you to save your finished crop using "DPI" (!) C'mon Serif!)
7 Sep 2020 10:35AM
Looks at this site https://www.calculatorsoup.com/calculators/math/percentage.php


uing their method the image you have shown is 2.29% of the original.

The link I have shown gives you how percentages are worked out - which I think is what you asked.
Jestertheclown 11 8.3k 253 England
7 Sep 2020 12:50PM
God's teeth Angie.

That has to be the most complicated method of working out percentages that I've ever seen!

Not that it relates to cropping of images in any way.
7 Sep 2020 1:44PM
I don't think that was what he asked. He wanted to know what percentage of the original was the image he showed - at least that was what I understood by his question. I don't think, myself that 'percentage' is a good method of cropping as it really is not giving you any choice as to where the crop would go - obviously it would be calculated from the centre whereas you may wish to take something off side and top or bottom. PS CC does do percentages - but I have never used it.
Jestertheclown 11 8.3k 253 England
7 Sep 2020 3:45PM

Quote:He wanted to know what percentage of the original was the image he showed

He did ask that and to find the answer's a simple matter although since it's not cropped using percentages, it doesn't really relate.

Quote:I have come across referances to percentage crop. How is this done?

He also asks about cropping using percentages as a guide, which I've explained above.
ARI 17 567 United Kingdom
7 Sep 2020 11:14PM
Crop was made from this file of croc pretending to be flotsam.

6761_1599516784.jpg
8 Sep 2020 12:02PM
I think what you're not understanding about a percentage crop is that the programme your using would decide where that crop would be. The photographer has decided where that crop will be, therefore it would have been decided either by a selected section or a cropping tool - both actually work in the same way. You can then discover what percentage it is of the whole but why do you need percentages? Most web sites and print shops, I believe, when asking for specific dimensions ask for Mb, Jpg, and perhaps maximum pixels x pixels.
Jestertheclown 11 8.3k 253 England
8 Sep 2020 7:39PM

Quote:I think what you're not understanding about a percentage crop

I understand perfectly how percentage crops work Angie; I went so far as to post a link explaining it to anyone who cares to look at it.
The problem here is that you're missing the point. Obviously, the photographer has taken a crop of his choosing but that's not how percentage cropping works.
In reality, I don't know quite why anyone would want to crop an image via percentages.
Yes, it's possible to work out how much of his shot is left (or gone) as a percentage of the original but as you say yourself, why would you bother?
With regard to websites/printers etc., they just require an image to be of their chosen variety of overall dimensions which may or may not (most likely not) have been achieved by cropping.
In fact, where size is concerned, cropping has more to do with maintaining or changing an aspect ratio than arriving at a final overall size.
That's what the resizing tool is for.
ARI 17 567 United Kingdom
9 Sep 2020 2:40PM
Going through pictures taken, I noticed that this animal has a 'milky' eye, hence I cropped it to look at it. It is a normal reptilian eye. However the resulting crop presented a more interesting composition than the full frame picture . I was intrigued to know the size of the crop as it is a more than passable representation of menace, danger of the animal as compared to its pose in the full fame. I am surprised at the result even though it is 2.29%, there is lots of detail to appreciate the animal in its environment as a stealthy ambush predator/hunter. You can examine, explore and enjoy the animal in safety, the best advantage of wildlife photography.
andy63 14 35 England
15 Sep 2020 7:50AM

Quote:Looks at this site https://www.calculatorsoup.com/calculators/math/percentage.php


using their method the image you have shown is 2.29% of the original.

The link I have shown gives you how percentages are worked out - which I think is what you asked.




1313 pixels is 15% of 8688 pixels, 875 pixels is 15% of 5792 pixels, not 2.29%

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