100% Crops?

[Dave Gurtcheff]

When folks here, and other forums want to show the detail a certain camera, or lens is capable of, they post "100% crops". I have done this myself, enlarging the image in Photoshop, until it says 100%. Please excuse the dumb question: 100% OF WHAT? It is not print size, not actual pixels. Again pardon the dumb question, but on another thread here, I was trying to illustrate a point with manual focusing with a 645D. After I posted, I started to wonder, "exactly what does this represent"? How big a print would this be (I know it depends on the megapixels on sensor).
Thanks in advance....
Dave

[feppe]

100% crop means an image which has been cropped from the original image and no resampling (resizing) has been done to it. They are often used to gauge image quality without having to post huge files, and avoiding copyright infringment of the whole image.

[Dave Gurtcheff]

100% crop means an image which has been cropped from the original image and no resampling (resizing) has been done to it. They are often used to gauge image quality without having to post huge files, and avoiding copyright infringment of the whole image.

Thanks Feppe. So what I showed on the Medium Format Section was not correct. The as shot RAW image was about 23"x31" @240 dpi. I should have cropped that and posted. What I did was enlarge the image on screen (using magnifing class or ctrl +) until it said 100%, then cropped that and posted.
Thanks again
Dave Gurtcheff

[bradleygibson]

It sounds like what you did was correct.  100% crop should more accurately be termed a 1:1 crop.  One image pixel maps directly to one screen pixel.  Zooming your image to 100% and doing a screen grab is a common way to make it--it's pretty easy to see why it's commonly called a 100% crop.

The only thing that matters is the presentation of exactly one image pixel to exactly one pixel on the output device--in this case, the screen.  100% crops are about pixels, and not presentation size, apparent resolution, viewing distances, etc., there are no PPI, DPI, inches, etc. involved.

HTH,
Brad

[feppe]

It sounds like what you did was correct.  100% crop should more accurately be termed a 1:1 crop.  One image pixel maps directly to one screen pixel.  Zooming your image to 100% and doing a screen grab is a common way to make it--it's pretty easy to see why it's commonly called a 100% crop.

The only thing that matters is the presentation of exactly one image pixel to exactly one pixel on the output device--in this case, the screen.  Because it's really about pixels, and not size, resolution, etc., there are no PPI, DPI, inches, etc. involved.

Exactly. Dave, as long as you didn't resample/resize the image before or after cropping, it's a 100% crop and you're ok. Zooming in or out doesn't resample the image.

_{Well, to be more accurate, it resizes on screen but not the file itself - not to confuse}

[PierreVandevenne]

Well, based on your description, you did well. (and a quick look at what you posted seems to show a texture that is what one expects in a 100% CCD crop).

[Dave Gurtcheff]

Thank you everyone. Happy New Year. I was trying to help people with what I had found for the way I work, then became concerned I may have unintentionally misled people.
Again, thanks
Dave