Terms used in crop

Started Jul 1, 2012 | Discussions
Frank
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Terms used in crop
Jul 1, 2012

In articles reviewing cameras, they show example photos which are described as
a "100% crop". What does that mean?

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corneaboy
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Re: Terms used in crop
In reply to Frank, Jul 1, 2012

You may not get much response because it has been discussed so much before.

It means there is a one to one relationship between the image pixels from your camera and the image that is displayed. It can refer to the entire image or any size crop as long as it meets that definition.

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apaflo
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Re: Terms used in crop
In reply to Frank, Jul 1, 2012

Frank wrote:

In articles reviewing cameras, they show example photos which are described as
a "100% crop". What does that mean?

It means that the image has not been resampled to change the pixel dimensions. Period.

Note that a "100% crop" does NOT mean that you will necessarily get a 1:1 image to display representation! It means that if you do have that relationship, what you see is what you get and that the display mechanism will not need to resample the image.

Lets look at examples to understand the significance. I have a Nikon D800 camera that produces images that are 7360x4912. I have a monitor that is set up for a 1600x1200 pixel display. Clearly I cannot view all of a 7360x4912 image at one time. If I am seeing the entire image, it necessarily has been resampled to something less that 1600x1200. Lets say that I am viewing in a window that is 1000x500 pixels, and that I can see the entire image... which means that it has been resampled at a 7.37:1 ratio and in essence, I'm actually seeing about 1 out of every 8 of the original pixels. The biggest significance is that I can't determine "sharpness" because of that. Therefore I can't really apply "Sharpen" or "Unsharp Mask" and expect to see exactly what effect it would have on a print made from the original.

So, if I then crop out a 1000x500 pixel section of that image, and display it in that same 1000x500 pixel window, I will indeed have a "100% crop" that is indeed being viewed at 1:1 monitor to display pixels. If I've applied Sharpen to the original 7360x4912 image, I may not be able to judge how effective it is looking at the entire image, but when looking at a 100% crop on a 1:1 basis the effects of Sharpen can be judged accurately.

However, the point that needs to be clear is that a "100% crop" section of an image is not necessarily viewed a 1:1. If I keep my 1000x500 window and view an image that was cropped at 800x400, or 1600x800, they will have to be resampled by the viewer to make them fit the 1000x500 window, and while they may each be a "100% crop" that isn't what I'd be viewing!

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AnthonyL
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Re: Terms used in crop
In reply to Frank, Jul 1, 2012

Frank wrote:

In articles reviewing cameras, they show example photos which are described as
a "100% crop". What does that mean?

Just go down less than a page on this forum for a recent discussion.

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Barrie Davis
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Re: Terms used in crop
In reply to Frank, Jul 1, 2012

Frank wrote:

In articles reviewing cameras, they show example photos which are described as
a "100% crop". What does that mean?

It means that the image from the camera is enlarged enough that each and every pixel on the sensor is alloted its own separate pixel on your monitor display. This is a "1-to-1 rate of display", also called "100%."

However, because the pixels on the monitor are so much larger than those on the sensor, at the 1-to-1 rate of display (100%), the whole image is very much larger than the tiny camera sensor... so much so there is not enough space on the screen for the whole picture at once.... the picture greatly overshoots the screen edges all around; you can only see all of it by scanning around in sequential fashion.

While scanning like this, any small section of the 100% image may saved-off separately from the whole image, and this small section is known as a "crop"...

.... a 100% crop
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Baz

"Ahh... But the thing is, they were not just ORDINARY time travellers!"

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AnthonyL
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Re: Terms used in crop
In reply to Barrie Davis, Jul 1, 2012

Barrie Davis wrote:

However, because the pixels on the monitor are so much larger than those on the sensor, at the 1-to-1 rate of display (100%), the whole image is very much larger than the tiny camera sensor... so much so there is not enough space on the screen for the whole picture at once....

And what happens if the image was taken in camera as an 800x600 jpg and I have a large 1600x1200 screen?

As I said in the other thread it is simply enough to state the 1:1 display ratio without getting into "bigger" "smaller" arguments.

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Barrie Davis
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Re: Terms used in crop
In reply to AnthonyL, Jul 1, 2012

AnthonyL wrote:

Barrie Davis wrote:

However, because the pixels on the monitor are so much larger than those on the sensor, at the 1-to-1 rate of display (100%), the whole image is very much larger than the tiny camera sensor... so much so there is not enough space on the screen for the whole picture at once....

And what happens if the image was taken in camera as an 800x600 jpg and I have a large 1600x1200 screen?

A JPEG of only 800 x 600 doesn't use all the pixels of the sensor, so cannot yield a 100% crop.

As I said in the other thread it is simply enough to state the 1:1 display ratio without getting into "bigger" "smaller" arguments.

You know very well why that was done.
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Baz

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apaflo
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Re: Terms used in crop
In reply to Barrie Davis, Jul 1, 2012

Barrie Davis wrote:

AnthonyL wrote:

Barrie Davis wrote:

And what happens if the image was taken in camera as an 800x600 jpg and I have a large 1600x1200 screen?

A JPEG of only 800 x 600 doesn't use all the pixels of the sensor, so cannot yield a 100% crop.

A JPEG with "only 800x600" can be displayed as a 100% crop on any screen with 800x600 or more pixels. It will very nicely fit, as a 100% crop, on a large 1600x1200 monitor screen.

It merely has to be displayed with 1 image pixel being represent by 1 display pixel, and there is absolutely no requirement to use any relative number or percentage of the screen's pixels.

Again, the single essential characteristic is that the image must not be resampled for viewing.

As I said in the other thread it is simply enough to state the 1:1 display ratio without getting into "bigger" "smaller" arguments.

You know very well why that was done.

Confusion and not understanding the significance of a 100% crop?

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sherwoodpete
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It is a misnomer
In reply to Frank, Jul 1, 2012

Frank wrote:

In articles reviewing cameras, they show example photos which are described as
a "100% crop". What does that mean?

This frequently-used term is a bit of a misnomer. It causes a lot of confusion - even among those who use the term themselves.

Let's break it down into two parts:

  • Crop - this is the easy one. It means to trim away some of the image around the edges. The part which remains is the new cropped version of the image. Often done in order to alter the composition, or remove distracting or uninteresting parts of the shot.

  • 100% - this is simple too. But nevertheless it still causes confusion. It means the image before cropping has not been resized or resampled. Often it is the straight unedited version of the image as it came out of the camera, but some editing such as altering white balance or brightness etc. may have been done. So 100% means the image contains the original pixels at their original size. Then it is cropped to give a much smaller result.

Why is this done? Well, the full image may be many megapixels in size. There may be some technical point such as sharpness, or chromatic aberration under discussion. Rather than supply the entire image, the small section of interest is cropped out and presented for examination by others.

There is a school of thought that the resulting cropped image can only be treated in one way. That is, it must always be viewed on a monitor at full size, that is with each image pixel matching a monitor pixel. Now that was fine when monitors used to have 640 x 480 pixels. Each pixel was easily large enough to see. Nowadays, we have larger, higher resolution monitors which may be viewed from further away. So the user may choose to zoom in and scrutinise the image more closely. Or a user may choose to print out the cropped image on paper.

All we need to know is how the image was prepared :
     a) it was not resized or resampled.
     b) it has been cropped.

What takes place afterwards is beyond your control. For example if the image is displayed in a browser window, it may be automatically resized (for display purposes) by the browser. Or it may be printed out. It may be examined in an image editor - who knows what users get up to?

Note, certain image defects at the pixel level may be difficult to preserve in a jpeg image, so the cropped image may be supplied in an uncompressed format such as PNG (convenient as it can be displayed in a browser) or TIFF. In this case, the complete, uncompressed image would result in a much larger file size, so the justification for cropping is even greater.

Regards,
Peter

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Barrie Davis
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Re: Terms used in crop
In reply to apaflo, Jul 1, 2012

apaflo wrote:

Barrie Davis wrote:

AnthonyL wrote:

Barrie Davis wrote:

And what happens if the image was taken in camera as an 800x600 jpg and I have a large 1600x1200 screen?

A JPEG of only 800 x 600 doesn't use all the pixels of the sensor, so cannot yield a 100% crop.

A JPEG with "only 800x600" can be displayed as a 100% crop on any screen with 800x600 or more pixels. It will very nicely fit, as a 100% crop, on a large 1600x1200 monitor screen.

It is merely full-sized viewing of an interpolated image...Therefore resized, therefore not a 100% crop of the sensor image.... (see above.)
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Baz

"Ahh... But the thing is, they were not just ORDINARY time travellers!"

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apaflo
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Re: Terms used in crop
In reply to Barrie Davis, Jul 1, 2012

Barrie Davis wrote:

apaflo wrote:

Barrie Davis wrote:

AnthonyL wrote:

Barrie Davis wrote:

And what happens if the image was taken in camera as an 800x600 jpg and I have a large 1600x1200 screen?

A JPEG of only 800 x 600 doesn't use all the pixels of the sensor, so cannot yield a 100% crop.

A flat statement that is not necessarily true.

A JPEG with "only 800x600" can be displayed as a 100% crop on any screen with 800x600 or more pixels. It will very nicely fit, as a 100% crop, on a large 1600x1200 monitor screen.

It is merely full-sized viewing of an interpolated image...Therefore resized, therefore not a 100% crop of the sensor image.... (see above.)

The sensor "image" is not an image, and has nothing at all to do with whether something is a 100% crop. Pixel binning for example, or any other method of interpolation that produces any given sized image is perfectly acceptable, even if it is 800x600. (And in fact there are cameras that produce such images!)

The real question is whether the original RGB image , regardless of which format, has been resampled or not. The idea that no 800x600 image could be a 100% crop is an absurdly narrow view.

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apaflo
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Re: It is a misnomer
In reply to sherwoodpete, Jul 1, 2012

sherwoodpete wrote:

All we need to know is how the image was prepared :
a) it was not resized or resampled.
b) it has been cropped.

What takes place afterwards is beyond your control. For example if the image is displayed in a browser window, it may be automatically resized (for display purposes) by the browser. Or it may be printed out. It may be examined in an image editor - who knows what users get up to?

If what takes place is beyond your control, the what you are viewing is not a 100% crop.

Viewing with a web browser is an excellent example, and while we can usually assume that it provides something close enough for non-critical work (for example to analyze for comments to be post here on DPR), it certainly is not appropriate for judging sharpening applied to an image before a print is made for a gallery display.

On the other hand, we can very easily have control simply by viewing with a typical image editor and selecting a 100% view. The editor can determine how many pixels the monitor screen has, and will display any given image accordingly.

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Barrie Davis
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Re: Terms used in crop
In reply to apaflo, Jul 1, 2012

apaflo wrote:

Barrie Davis wrote:

apaflo wrote:

Barrie Davis wrote:

AnthonyL wrote:

Barrie Davis wrote:

And what happens if the image was taken in camera as an 800x600 jpg and I have a large 1600x1200 screen?

A JPEG of only 800 x 600 doesn't use all the pixels of the sensor, so cannot yield a 100% crop.

A flat statement that is not necessarily true.

It is necessarily true, until you find such camera with a sensor of only 600 x 800 pixels, or fewer.

So why don't you pop off now and go look for it instead of making a nuisance of yourself here?

A JPEG with "only 800x600" can be displayed as a 100% crop on any screen with 800x600 or more pixels. It will very nicely fit, as a 100% crop, on a large 1600x1200 monitor screen.

It is merely full-sized viewing of an interpolated image...Therefore resized, therefore not a 100% crop of the sensor image.... (see above.)

The sensor "image" is not an image and has nothing at all to do with whether something is a 100% crop.

Since when is the sensor image "not an image?" Do you even know what you're trying to get across, here?

Pixel binning for example,

Pixel binning is interpolation. Interpolation is, by definition, NOT 100% viewing of the image from the sensor.

or any other method of interpolation that produces any given sized image is perfectly acceptable, even if it is 800x600. (And in fact there are cameras that produce such images!)

Not without interpolation there aren't... and it is images without interpolation in pixel count we are talking about. That's the whole point of what people mean by "100%," and is what the OP was enquiring about.

Perhaps you could go away and bother somebody else with your deliberate and spiteful acts of confusion? Or maybe spend your time seeking that camera with a sensor having pixel dimensions of 800 x 600 or fewer. Good luck with that!

The real question is whether the original RGB image , regardless of which format, has been resampled or not.

So, what was the point of all your rubbish about pixel binning?
Pixel binning and interpolation are both resampling.
Or are you gonna start another pointless argument about that?

The idea that no 800x600 image could be a 100% crop is an absurdly narrow view.

Huh! I think it was YOU that introduced the absurdly narrow view of an image with only 800 x 600 pixels to this thread, was it not?
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Baz

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corneaboy
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Re: It is a misnomer but one more try.
In reply to sherwoodpete, Jul 1, 2012

The 100% crop is an attempt to standardize the appearance of the image for comparisons to other images for quality.

Lets say your camera takes as photo that is 2000x3000 pixels and you have a monitor that displays 2000x3000 pixels. There would be a one to one ratio between the photo as taken and the monitor pixels and the picture would just fill the screen. Now suppose you crop parrt of the image so it is 1000x1500 pixels. The image will now fill only part of the screen but you haven't changed the ratio of pixels in the original photo to pixels on the screen. The size of the crop doesn't matter. Next you resize the cropped image so it fits the screen. Your software has to add pixels which it does by interpolating the pixels that are available, known as upsampling. This changes the appearance (quality ) of the image. You no longer have a 100% crop.

So as others have said the important thing is to crop without resampling. The image must then be viewed on your monitor without resampling.

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Barrie Davis
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Don't compare at 100%
In reply to corneaboy, Jul 1, 2012

corneaboy wrote:

The 100% crop is an attempt to standardize the appearance of the image for comparisons to other images for quality.

Only images with the same number of pixels on their respective sensors can be accurately compared at a common 100% viewing rate.

Sensors with different pixel counts, even if of the same physical dimensions, will yield different on-screen magnifications if both displayed at 100%, and this can be very misleading in regard of actual quality attained.

The higher pixel count image gets magnified more, and this leads many people to believe their new "superior" camera (with more pixels) produces pictures which are less sharp than their old one...

To compare images directly they need to be viewed at the same physical size on screen (say 15" across), NOT at the same percentage rate of distribution of pixels... (not 100%, or any other percentage in common.)
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Baz

"Ahh... But the thing is, they were not just ORDINARY time travellers!"

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corneaboy
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Re: Don't compare at 100%
In reply to Barrie Davis, Jul 1, 2012

So would the following be consistent with your point?
Camera 1 is 2000 pixels wide.
Camera 2 is 4000 pixels wide and same sensor size.
Monitor is 2000 pixels wide.
Camera 1 image fills the screen.
Camera 2 image is twice the screen size.
Both images are 100%crop.

Seems to me that both images would look the same as far as resolution goes since they would have the same pixels per unit distance.

However, Camera 2 image is really better because it has the potential to double the resolution if you wanted, for example, to make prints the same size from the two cameras.
Another scenario
Camera 2 is 4000 pixels wide but twice the sensor size.
Image resolution is the same as Camera 1 but has twice the field of view.
Therefore, a comparison of 100% crop is misleading.

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apaflo
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Re: Don't compare at 100%
In reply to Barrie Davis, Jul 1, 2012

Barrie Davis wrote:

corneaboy wrote:

The 100% crop is an attempt to standardize the appearance of the image for comparisons to other images for quality.

Only images with the same number of pixels on their respective sensors can be accurately compared at a common 100% viewing rate.

Not true, and in addition there is absolutely no value whatever to retaining exactly the same number of pixels as there are data locations from the sensor.

The sensor has nothing to do with whether any given image can be considered a 100% crop of some other given image!

Sensors with different pixel counts, even if of the same physical dimensions, will yield different on-screen magnifications if both displayed at 100%, and this can be very misleading in regard of actual quality attained.

The higher pixel count image gets magnified more, and this leads many people to believe their new "superior" camera (with more pixels) produces pictures which are less sharp than their old one...

To compare images directly they need to be viewed at the same physical size on screen (say 15" across), NOT at the same percentage rate of distribution of pixels... (not 100%, or any other percentage in common.)

That has nothing to do with a 100% crop.

As an example, if we have a camera that produces a 1024x768 pixel image, and regardless of the characteristics of the sensor that produced it, we want to print it on an Epson printer (360 Pixels Per Inch) and produce an 8x10 inch print that is as sharp as possible... we first must resample the image to 2880x3600 pixels and then we need to use a Sharpen tool on the resulting image. But if our monitor has a 1600x1200 screen we cannot view the 2880x3600 image all at once to judge what the Sharpen tool does.

And that is where a 100% crop view is used!

We need to view part of the 2880x3600 image cropped to a size that allows one pixel of the image to be displayed by one pixel on the screen. Otherwise when the Sharpen tool is applied the result we see on screen will not be the same as the result seen when printed.

So a section from the original RGB image at 2880x3600 must be cropped to something smaller than 1600x1200 and displayed in a same sized window. If our editor is currently using a window that is 1048 pixels wide by 932 pixel high, we need for the editor to crop out a 1048x932 section of the total 2880x3600 pixels and display it.

Clearly what we are discussing has no connection to the number of data locations produced by the original sensor in the camera, with the RAW file, or for that matter even with the original image produced by demosiacing the RAW data! It has only to do with the image that will be sent to the printer, and viewing that image without further resampling.

( Barrie Davis needs to listen to carefully to corneaboy , who has it nailed!)

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sherwoodpete
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Png Example
In reply to sherwoodpete, Jul 1, 2012

sherwoodpete wrote:

Note, certain image defects at the pixel level may be difficult to preserve in a jpeg image, so the cropped image may be supplied in an uncompressed format such as PNG (convenient as it can be displayed in a browser) or TIFF. In this case, the complete, uncompressed image would result in a much larger file size, so the justification for cropping is even greater.

Here's an example where a lossless format such as PNG is useful.

100% crop:

Those of you with excellent eyesight will have spotted the horizontal green bar, which is an image defect (you may need to zoom in to see it).

Just in case you've not located it, here's a link to a 16x enlarged version (200x200px image):
http://i.pbase.com/o6/97/598597/1/144440120.W9keAiqz.P3140011_crop3x16.png

This example taken from the 5MB original at Dcresource.com. http://www.dcresource.com/reviews/olympus/c7070wz-review/P3140011.JPG

First pointed out in this thread:
http://forums.dpreview.com/forums/read.asp?forum=1008&message=15879116

Regards,
Peter

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altis
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Re: Terms used in crop
In reply to Barrie Davis, Jul 1, 2012

Barrie Davis wrote:

It is necessarily true, until you find such camera with a sensor of only 600 x 800 pixels, or fewer.

Here's a total unresized shot from my first digital camera. It's all of 288 x 352 pixels. Enjoy it in all its 100% glory:

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AnthonyL
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Re: Terms used in crop
In reply to altis, Jul 1, 2012

altis wrote:

Barrie Davis wrote:

It is necessarily true, until you find such camera with a sensor of only 600 x 800 pixels, or fewer.

Here's a total unresized shot from my first digital camera. It's all of 288 x 352 pixels. Enjoy it in all its 100% glory:

Thanks for posting, and here is a 100% crop from that photo (hope you don't mind)

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