50%, 100%, 75% crop

Left Handed Brisket wrote in post #18572722
What?

I think I get what you are trying to say, but man, this is just too much when all that needed to be said I put in bold.

When I see a post that is really long, and technical or mathematical in nature (even slightly so), I just skip over it.

I like Wilt, but honestly, who is actually going to read such a thing?

.

Tom Reichner wrote in post #18572726
When I see a post that is really long, and technical or mathematical in nature (even slightly so), I just skip over it.

I like Wilt, but honestly, who is actually going to read such a thing?

.

He used the term mythical, imo, it is simply irrelevant obfuscation. Especially in the context of this thread.

Sorry, wilt.

The OP, and others' confusion is due mostly to applying terminology incorrectly. It is industry jargon and looking at it from the point of view of whether something exists (100% or 0%) is where the confusion lies.

agedbriar wrote in post #18572604
Posting "a 100% crop" (usually for some technical evaluation of the picture) means taking a small section of the picture, a section small enough to be viewed without downsizing (at 100% a.k.a. 1:1 magnification a.k.a. pixel to pixel) on most monitors.

Actually, the 100% relates to viewing, not to the amount of cropping.

This is the precise explanation. You are taking a crop (for example, on this forum, a 1280x1280 pixel crop) of the pixels in the image when viewed at 100% "zoom" so that one pixel in the display equals one pixel in the file (no image scaling done by the software or the video card). As others have mentioned, this kind of image is usually used to assess something like sharpening, noise, demosaic artifact, etc., where you want to see the data as it is in the file, not interpolated or extrapolated by the software or hardware used to view it.

kirk

kirkt wrote in post #18572760
As others have mentioned, this kind of image is usually used to assess something like sharpening, noise, demosaic artifact, etc., where you want to see the data as it is in the file, not interpolated or extrapolated by the software or hardware used to view it.

kirk

Pixel peeping in a word.

Left Handed Brisket wrote in post #18572722
What?

I think I get what you are trying to say, but man, this is just too much when all that needed to be said I put in bold.

Tom Reichner wrote in post #18572726
When I see a post that is really long, and technical or mathematical in nature (even slightly so), I just skip over it.

I like Wilt, but honestly, who is actually going to read such a thing?

.

OP wanted to UNDERSTAND the topic. He did state, "can someone explain how they get a "50% crop" on an image? or a 100% crop?"
Merely saying, "the embedded EXIF data for 'dpi' simply does not matter to your computer display" does not lead to understanding, it only states what does NOT apply.

My prior post was long simply because it presented three examples (after the preface), so he could test his understanding against each of the situations.

A 100 % percent crop as I see it is the size of your original file then reduced in size so for example a 6400pixal long edge image when cropped 100 % produces roughtly 1055pixal long edge image.

To then display the image on a scream without image suffering would need a screen of less than 1055pixals along the long side.

P.

Original image then a 100% crop from the center.

P.

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But for some of us, a 100 percent crop doesn't really exist. . Why? . Well, because I use a 5k monitor, and the photos I take are either 4368 or 4752 or 4896 pixels on the long edges. . So when I view these images at 100%, no cropping has been done.

I am attaching the following image to illustrate my point. The image is of my entire monitor screen when I am viewing this Elk photo at 100%. If I viewed the same image on my old monitor that was only, like, 2400 pixels across, then it would look very different, as if I haad zoomed in to just view a part of the image.

I think too many people are confusing the term crop with viewing scale. A 100% crop is based on ratios of length and width, while viewing scale is based on magnification of the projected area.

If I have an image that is natively captured at (as an example) 6000 x 4000 and I maintain that ratio but resize the image to 3000 x 2000 without removing anything from the image it is a 100% crop (just resized). However, if I use a crop tool and physically remove parts of my image (without resizing) in order to "zoom in" on a subject, down to 3000 x 2000 I have effectively cropped the image 50%. However, if that same 6000x4000 image was scaled down to 3000 x 2000, the image area would still be 100% but the file dimensions would be at 50%.

So in the example above;

100% crop for a 6000 x 4000 pixel image is a 1:1 ratio of the image area, regardless of pixel density.

50% crop where pixels are removed is a 2:1 ratio of the image area, regardless of pixel density.

BUT... if I had a monitor with a resolution of 3000 x 2000 I could view that 50% cropped image at 100% while I would have to view the 100% cropped image at 50% in order to see the full image.

Yeah, I know...

100% crop

100% is the important part, and it means full unmolested resolution.

ANY image that has not been reduced in size (interpolated, reduced resolution) to a smaller number of pixels from as shot.

The "crop" part is almost an afterthought. It's just a favor we did in the old days of low bandwidth and small monitors to help our fellows get the detail without the huge file size. It still applies today as image res (MegaPickles) continues to increase.

It means "this is the image detail as seen at 100% on YOUR monitor. What monitor I used to edit is of no importance! No re-sizing was done. This is the actual image detail. oh and by the way, to make it more portable, I cropped out a nice example part for you"

P.S. "If the crop is too large to fit on your screen in it's entirety without resizing, then it's up to you to look at it at 100% and scroll. If you have a 6K monitor, sorry it may appear as a postage stamp to you, but don't blow it up beyond 100% scale or you will lose the intent of my post"

The idea is to;

A - Show full res detail, unmolested by resizing.

B - Make it more portable by cropping out a specific area as an example rather than posting a 14MB full size image that will offer no more info than the 100% crop.


All of the above is fact.


This is opinion (mine)
Any other XX% in front of "crop" defeats the purpose, and there for IMHO both loses it's value, and loses its meaning in translation. But that's just my feeling.

IF we accept the above 100% part as Hoyle, as Marquess of Queensberry rules, then a 50% crop SHOULD mean, Reducing full size image to 50% of its original resolution, and then making a crop of that to show as an example of the resulting re-size.

CyberDyneSystems wrote in post #18572935
This is opinion (mine)
Any other XX% in front of crop defeats the purpose, and there for IMHO both loses it's value, and loses its meaning in translation. But that's just my feeling.

I don't mean to ague with you, Jake, especially considering that you clearly said that this is just your opinion. . But ......

If someone posts a close-up of a bird, and I ask them,

"Is this photo uncropped or cropped? If cropped, then how much did you crop it?"

Well, in that kind of circumstance, which actually happens with regularity, I find their response extremely valuable, especially if it is specific and numeric. The answer, "it is a heavy crop" doesn't really do me any good at all unless I know precisely how heavy of a crop it is.

I NEED precise information about the cropping so that I can fully assess their methods and techniques, and try to figure out how I can use them in my own photography. . This is especially useful in situations where they are shooting at some kind of set-up that I myself am going to be shooting at, where you can't just get closer or further away from the subject because of various parameters that limit the photographer's freedom to move about.

All this being said, the "50% crop" or "80% crop" lingo can be confusing, because I don't always know if they are referring to a percentage of the overall area of the image, or if they are instead referring to a percentage of the longest dimension, in pixels.

If an image was originally 3600 pixels across by 2400 pixels high, for a total pixel count of 8.64 MP, then a "50% crop" could mean that it has been cropped down to where only half of the original pixels are remaining - a 4.32 MP image. . Or, it could mean that it has been cropped to 1800 pixels by 1200 pixels, which would result in a 2.16 MP image.


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Tom Reichner wrote in post #18572958
I don't mean to ague with you, Jake, especially considering that you clearly said that this is just your opinion. . But ......

If someone posts a close-up of a bird, and I ask them,

"Is this photo uncropped or cropped? If cropped, then how much did you crop it?"

Well, in that kind of circumstance, which actually happens with regularity, I find their response extremely valuable, especially if it is specific and numeric. The answer, "it is a heavy crop" doesn't really do me any good at all unless I know precisely how heavy of a crop it is.

I NEED precise information about the cropping so that I can fully assess their methods and techniques, and try to figure out how I can use them in my own photography. . This is especially useful in situations where they are shooting at some kind of set-up that I myself am going to be shooting at, where you can't just get closer or further away from the subject because of various parameters that limit the photographer's freedom to move about.

All this being said, the "50% crop" or "80% crop" lingo can be confusing, because I don't always know if they are referring to a percentage of the overall area of the image, or if they are instead referring to a percentage of the longest dimension, in pixels.

If an image was originally 3600 pixels across by 2400 pixels high, for a total pixel count of 8.64 MP, then a "50% crop" could mean that it has been cropped down to where only half of the original pixels are remaining - a 4.32 MP image. . Or, it could mean that it has been cropped to 1800 pixels by 1200 pixels, which would result in a 2.16 MP image.

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Like the photo I posted above shot with the 24mp D7100 then cropped from the center to about 100% then ouputted with the file showing the remaining pixal size image.

P.

Tom Reichner wrote in post #18572958
If an image was originally 3600 pixels across by 2400 pixels high, for a total pixel count of 8.64 MP, then a "50% crop" could mean that it has been cropped down to where only half of the original pixels are remaining - a 4.32 MP image. . Or, it could mean that it has been cropped to 1800 pixels by 1200 pixels, which would result in a 2.16 MP image.

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A 3600x2400 where section is cut out that is now 1800x1200 isn't a 50% crop, you have 1/4th the total image, not 1/2 the total image. If you take roughly 71% of the width and 71% of the height (if you want to keep the same aspect ratio), then the final 50% crop out of the image would give you a 2550 x 1700 final result.

Since a crop factor is a product of height and width, you need the square root.

Pagman wrote in post #18572959
Like the photo I posted above shot with the 24mp D7100 then cropped from the center to about 100% then ouputted with the file showing the remaining pixal size image.

P.

Your resulting size is nothing more than an indicator of what you cropped out of the image, it is not any kind of metric for others to use. I could crop out a 20x20 grid of pixels from my image and then post it.

TeamSpeed wrote in post #18572977
A 3600x2400 where section is cut out that is now 1800x1200 isn't a 50% crop, you have 1/4th the total image, not 1/2 the total image. If you take roughly 71% of the width and 71% of the height (if you want to keep the same aspect ratio), then the final 50% crop out of the image would give you a 2550 x 1700 final result.

Since a crop factor is a product of height and width, you need the square root.

True, but the 50% percentage number is showing what percentage of pixels (in one direction) of the image have to be 'ignored' by the display driver software, in outputting 3600 pixel wide image to fit 1800 pixel wide monitor space.

OTOH, when I 'crop' an image so that you see a small fraction of the total image, my own convention is to mention that I am showing '10% of the image (area)' and not 10% of the width/length.

So 'it depends' upon context.