good explanation of "100% crop"?

[Toeslider]

I did a search, but of course that returns to me every thread where someone has posted one and tagged it "100% crop".

Can someone direct me to an explanation of what exactly a 100% crop is, what it's good and not so good for, etc.? I thought I kind of understood the concept, but now I'm not so sure. I know how to make one, but I'm not so sure I understand what it can tell me, aside from comparing it to other 100% crops for sharpness, CA, etc.

[Toeslider]

Edit, nevermind. Of course now that I have posted this I see several "related threads" below that will probably answer my question...

[Bobster]

100% crop is taking a portion of a photograph, zoomed in at 100% of its pixel size

so taking a 20D file as an example, at 3504 x 2336px, you would take a 300x300px area from that file to show details, sharpness, CA etc..

[Toeslider]

I read through all the threads about it I came across, and there still seems to be some randomness to it based on who is doing it, viewing it, on what screen etc.

It seems the most widely accepted convention is to take an image in Photoshop (for example), set the zoom level to 100%, then crop out an easily manageable sized portion of the image to display for others to see image quality. I'm still wrapping my head around this, as it seems the amount of zoom you see in the cropped image would vary based on the size of the sensor you are using, so for comparisons your best bet would be to compare crops from the same sized sensor. In other words, a 100% crop from a 5d camera is going to show you a smaller portion of the image than a 100% crop taken with a 300d, assuming the images show the same scene to begin with. Does that make sense?

[SkipD]

I read through all the threads about it I came across, and there still seems to be some randomness to it based on who is doing it, viewing it, on what screen etc.

It seems the most widely accepted convention is to take an image in Photoshop (for example), set the zoom level to 100%, then crop out an easily manageable sized portion of the image to display for others to see image quality. I'm still wrapping my head around this, as it seems the amount of zoom you see in the cropped image would vary based on the size of the sensor you are using, so for comparisons your best bet would be to compare crops from the same sized sensor. In other words, a 100% crop from a 5d camera is going to show you a smaller portion of the image than a 100% crop taken with a 300d, assuming the images show the same scene to begin with. Does that make sense?Merely crop out a hunk of an image file from the camera and DO NOT RESIZE IT (either before or after cropping - use the camera's native size). The crop needs to be within the allowable pixel count of the forum's rules. That's it.

By the way, you would not want to save the cropped image back to the original filename. Always use "save as...." so that your original stays intact.

[Wilt]

I read through all the threads about it I came across, and there still seems to be some randomness to it based on who is doing it, viewing it, on what screen etc.

It seems the most widely accepted convention is to take an image in Photoshop (for example), set the zoom level to 100%, then crop out an easily manageable sized portion of the image to display for others to see image quality. I'm still wrapping my head around this, as it seems the amount of zoom you see in the cropped image would vary based on the size of the sensor you are using, so for comparisons your best bet would be to compare crops from the same sized sensor. In other words, a 100% crop from a 5d camera is going to show you a smaller portion of the image than a 100% crop taken with a 300d, assuming the images show the same scene to begin with. Does that make sense?

Yes, this is true! The mistaken belief that comparing two different cameras simply by comparing two 100% crops... if I take 200 x 200 pixels, I get only 5.3% of the 5DII frame height vs. 8.6% of the 20D/30D frame height., but both would appear to be the same amount of space of the 19" 1280 x 1024 LCD it is viewed upon.

[Toeslider]

Yes, this is true! The mistaken belief that comparing two different cameras simply by comparing two 100% crops... if I take 200 x 200 pixels, I get only 5.3% of the 5DII frame height vs. 8.6% of the 20D/30D frame height., but both would appear to be the same amount of space of the 19" 1280 x 1024 LCD it is viewed upon.


That's what I was thinking, and I don't think everyone understands this. For example, if I frame up a scene with both a 50d and a 300d, so that the same exact scene is seen in the viewfinder and on the final full print, then zoom them both to 100% in photoshop and take a 200 x 200 pixel hunk out of each of them and save as a "100% crop", the 100% crop images will be the same size on my screen, but will show different content, correct? (This is assuming the center point of the crop is the same for both.)

I'm sure this confounds other people as well, because I know if I look hard enough I can find 100% crops that people have posted using the same camera and lens, and one persons 100% crop will be a quarter of their image and another's will be 1/10th of their image, yet they will be the same size on my screen.

[Wilt]

That's what I was thinking, and I don't think everyone understands this. For example, if I frame up a scene with both a 50d and a 300d, so that the same exact scene is seen in the viewfinder and on the final full print, then zoom them both to 100% in photoshop and take a 200 x 200 pixel hunk out of each of them and save as a "100% crop", the 100% crop images will be the same size on my screen, but will show different content, correct? (This is assuming the center point of the crop is the same for both.)

I'm sure this confounds other people as well, because I know if I look hard enough I can find 100% crops that people have posted using the same camera and lens, and one persons 100% crop will be a quarter of their image and another's will be 1/10th of their image, yet they will be the same size on my screen.

Yup, using my example of 5.3% of the 5DII frame height vs. 8.6% of the 20D/30D frame height, I see a much smaller fraction of the total frame area, viewing the 5DII image at 100%

Unfortunately, if you ask instead to view the same percentage of the full frame, you are subject to the vaguaries of pixel interpolation in software, so that what you see is not necessarily reprsentative of the available detail in the source image. For example, if you display a 1280x1024 image onto multiple brand/models of projectors who all have native 1024x768 resolution, some of the projectors will display the text within the 1280x1024 image at a much higher level of quality than a different projector would display the same image.

[tonylong]

I'm sure this confounds other people as well, because I know if I look hard enough I can find 100% crops that people have posted using the same camera and lens, and one persons 100% crop will be a quarter of their image and another's will be 1/10th of their image, yet they will be the same size on my screen.

Not sure what you are referring to here. If you have the same camera/lens combo and take the same scene with the same settings, a 100% crop from each at the same point in the scene with the same pixel dimensions would display at those same dimensions (assuming you are using a straight display rather than some resizing behind the scenes).

But, as you say, it differs with cameras with different pixel densities.

People use 100% crops for a few things, such as sharpness and noise. You can compare two camera bodies for pixel-level sharpness or noise, although it becomes iffy if you are trying to pinpoint exact comparisons without very controlled testing setups. These are interesting and informative up to a certain point, but can become a bit myopic after a while:).

I examine my images closely for noise and sharpness images, and once in a while I'll post a 100% crop of an image if I want to illustrate something, such as relative lens sharpness or relative noise level, but remember that normal viewing is of the image overall.

[Wilt]

I examine my images closely for noise and sharpness images, and once in a while I'll post a 100% crop of an image if I want to illustrate something, such as relative lens sharpness or relative noise level, but remember that normal viewing is of the image overall.

Toeslider,
The issue under discussion is how apropos (or not) is comparison of 100% crops if the pixel density is considerably different. For example, if lens diffraction was fixed at 0.1mm (wild number pulled out of the air for discussion) and one camera had 3 pixels across that distance while the other had 4 pixels across that same distance, what has been proved? Only that the higher number of pixels is better at portraying the limitations of the lens! The same lens diffraction is spread over a larger area of the monitor, by the sensor which has a higher pixel density.

[Toeslider]

Not sure what you are referring to here...

I'll have to see if I can find a specific example, but basically what I am saying is that I think some people misinterpret what a "100% crop" is, or should be. I don't know how else to explain it, but I have seen examples posted in the same thread that were obviously gotten by different methods, and I'm sure each person was posting up what they thought was a "100% crop" by everyones standards.

It has been mentioned in other threads, but for the sake of comparison there really should be a definitive series of steps to go through to obtain a "100% crop", that everyone can do with a minimal investment in software.

Anyway, this isn't the first discussion on the topic, and it certainly won't be the last. It has answered a few questions for me and cleared up a few things for me. I don't know why, but without thinking about it too much I was of the belief that a "100% crop" would give you some indication as to how an image would print, but now that I think about it I realize that it has almost no bearing on that in general terms. If you apply it to the final output you intend to produce it might give you some indication of something, but I was mistakenly thinking it would give you a sample of what a section of your printed image would look like, but that would only be the case for an image printed at one specific set of parameters.

[Toeslider]

Toeslider,
The issue under discussion is how apropos (or not) is comparison of 100% crops if the pixel density is considerably different. For example, if lens diffraction was fixed at 0.1mm (wild number pulled out of the air for discussion) and one camera had 3 pixels across that distance while the other had 4 pixels across that same distance, what has been proved? Only that the higher number of pixels is better at portraying the limitations of the lens! The same lens diffraction is spread over a larger area of the monitor, by the sensor which has a higher pixel density.

Now that I am actually sitting down and thinking about what I am looking at, I understand that. It is a useful tool, but only if you compare apples to apples. In reading discussions on here it becomes apparent that not everybody understands that.

[LV Moose]

As someone relatively new to digital, this discussion makes me crazy. Here's how my simple mind sees "cropping":

100% crop: you've got nothing left, because you've cropped the whole damn thing.

Crop TO 100%: You haven't cropped anything, and you've still got the whole image.

75% crop: You've got 25% of the image area left, because you got rid of 3/4ths of it.

Crop TO 75%: You've still got 3/4ths.

50% crop, and crop TO 50%: Both are the same, you've got either an image that's half full, or half empty, depending upon your personality.

[Wilt]

As someone relatively new to digital, this discussion makes me crazy. Here's how my simple mind sees "cropping":

100% crop: you've got nothing left, because you've cropped the whole damn thing.

Crop TO 100%: You haven't cropped anything, and you've still got the whole image.

75% crop: You've got 25% of the image area left, because you got rid of 3/4ths of it.

Crop TO 75%: You've still got 3/4ths.

50% crop, and crop TO 50%: Both are the same, you've got either an image that's half full, or half empty, depending upon your personality.

Yeah, this dammed digital lingo is all twisted up!

To simplify...cut a section of pixels from the original frame, such that you can display all of the section on the monitor, subject to the posting limitations of the forum which you are posting it to.

'100% crop' is 'crop of a photo, allowing pixels to be viewed all at once on LCD at a 1:1 relationship between pixels in the photo and pixels of the monitor (at 100% magnification display)'

[tonylong]

As someone relatively new to digital, this discussion makes me crazy. Here's how my simple mind sees "cropping":

100% crop: you've got nothing left, because you've cropped the whole damn thing.

Crop TO 100%: You haven't cropped anything, and you've still got the whole image.

Heh! Yeah, you have your terminology mixed up! The 100% refers to how a shot is shown on your screen, not to some set portion of the image. If you show the shot at your native screen resolution, you are viewing it at "100%", which makes most of our images quite large but also shows the finest detail without breaking up pixels from discreet details into blocks of screen pixels representing individual image pixels. Crop a portion of that that can be viewed by most people in a Web browser with no shrinking, then you have a 100% crop.

[Toeslider]

Heh! Yeah, you have your terminology mixed up! The 100% refers to how a shot is shown on your screen, not to some set portion of the image. If you show the shot at your native screen resolution, you are viewing it at "100%", which makes most of our images quite large but also shows the finest detail without breaking up pixels from discreet details into blocks of screen pixels representing individual image pixels. Crop a portion of that that can be viewed by most people in a Web browser with no shrinking, then you have a 100% crop.


That's the best definition I have heard yet. I was going to ask exactly what Photoshop is displaying when your zoom is 100%, but I think that explains it. So 100% zoom is a 1 sensor pixel to 1 screen pixel relationship?

[LV Moose]

Heh! Yeah, you have your terminology mixed up! The 100% refers to how a shot is shown on your screen, not to some set portion of the image. If you show the shot at your native screen resolution, you are viewing it at "100%", which makes most of our images quite large but also shows the finest detail without breaking up pixels from discreet details into blocks of screen pixels representing individual image pixels. Crop a portion of that that can be viewed by most people in a Web browser with no shrinking, then you have a 100% crop.

As in... going to the "view" menu in DPP and selecting "view 100%"? Why didn't someone just say that? :)

I think it's you guys that have your terminology mixed up!:lol:

Oi vey! Such a headache I'm getting!

[cdifoto]

I did a search, but of course that returns to me every thread where someone has posted one and tagged it "100% crop".

Can someone direct me to an explanation of what exactly a 100% crop is, what it's good and not so good for, etc.? I thought I kind of understood the concept, but now I'm not so sure. I know how to make one, but I'm not so sure I understand what it can tell me, aside from comparing it to other 100% crops for sharpness, CA, etc.
View at full size and cut a chunk out.

[Wilt]

That's the best definition I have heard yet. I was going to ask exactly what Photoshop is displaying when your zoom is 100%, but I think that explains it. So 100% zoom is a 1 sensor pixel to 1 screen pixel relationship?


Hey whattamI, chopped liver?! :confused: ;) I said in message #14 "'100% crop' is 'crop of a photo, allowing pixels to be viewed all at once on LCD at a 1:1 relationship between pixels in the photo and pixels of the monitor (at 100% magnification display)'"

[tonylong]

That's the best definition I have heard yet. I was going to ask exactly what Photoshop is displaying when your zoom is 100%, but I think that explains it. So 100% zoom is a 1 sensor pixel to 1 screen pixel relationship?

Exactly, and a 100% crop takes a portion of that view so it can be displayed on a normal display size in a browser without shrinking in some artificial way. This ensures that critical image detail will not be lost.

As in... going to the "view" menu in DPP and selecting "view 100%"? Why didn't someone just say that? :)

I think it's you guys that have your terminology mixed up!:lol:

Oi vey! Such a headache I'm getting!

Heh! As The World Turns:)!

[chauncey]

All I do is take a marquee tool and set the pixel parameters to the size that I want displayed, usually 1,000 x 1,000 pixels, and crop out that chunk.