Stupid Question of 2009 !!!!!

[Chief]

I posted this question on aother forum and wanted to ask it here???

Gordon

Will someone explain the crop factor to me please!! I see a of a picture then someone says to crop it 100%. So they repost and it's just blown up to emphasize a certain area. Is there a rule of thumb to go by or is it just a yuppie word to enlarge an area...I used to think I was fairly intelligent until I ran into this thing called CROP. There has to be a better word or way?

Gordon

( I can hardly wait till viagra starts using it in commercials ...)

[srwatters]

I think you're mixing metaphors here. IMHO the 'crop factor' refers to the size of the sensor in relation to a standard size. i.e. for 35mm format DSLR bodies that would be in reference to the 24x36mm standard size for film. Nikon's crop sensor in the D300 is a 1.5x crop factor while the D700 is a 1x crop factor. In medium format bodies like my Hasselblad H2 that shoot 645, the standard size is that of 120 film which is 56x41.5mm. My PhaseOne P45 digital back has a sensor size of 49.1x36.8mm for a crop factor of 1.1.

If someone refers to a 100% crop, that typically means that they are not resizing the image, but taking the original pixels as shot and only displaying a portion of them. For example, the P45 shoots 7216x5412 pixels total. It is impossible to display all those pixels on any single monitor that I know of, so if you want to see the detail without resizing, I can take only a portion and 'crop' it so you still see the original pixels without having to scroll horizontally or vertically. Make sense?

[Chief]

Originally Posted by srwatters

I think you're mixing metaphors here. IMHO the 'crop factor' refers to the size of the sensor in relation to a standard size. i.e. for 35mm format DSLR bodies that would be in reference to the 24x36mm standard size for film. Nikon's crop sensor in the D300 is a 1.5x crop factor while the D700 is a 1x crop factor. In medium format bodies like my Hasselblad H2 that shoot 645, the standard size is that of 120 film which is 56x41.5mm. My PhaseOne P45 digital back has a sensor size of 49.1x36.8mm for a crop factor of 1.1.

If someone refers to a 100% crop, that typically means that they are not resizing the image, but taking the original pixels as shot and only displaying a portion of them. For example, the P45 shoots 7216x5412 pixels total. It is impossible to display all those pixels on any single monitor that I know of, so if you want to see the detail without resizing, I can take only a portion and 'crop' it so you still see the original pixels without having to scroll horizontally or vertically. Make sense?

Not really Scott ? But I'm working on it..Maybe it should be called Zoom or resize??

Happy New Year

Gordon

[srwatters]

To quote my favorite movie:
Inigo Montoya:"Let me explain... No there is too much. Let me sum up..."

Here is a web size image:


Here is the full size image as captured by my P45 digital back:
39MP Image Link

Here is a 100% crop of Lorie's eye:


If you overlay the crop on top of the full size image, you'll see the pixels are the same. That's the definition of a crop. It's just a portion of the full image versus a digital resizing (interpolation, the first image above) of the full image either larger or smaller.

[Chief]

Originally Posted by srwatters

To quote my favorite movie:
Inigo Montoya:"Let me explain... No there is too much. Let me sum up..."

Here is a web size image:


Here is the full size image as captured by my P45 digital back:
39MP Image Link

Here is a 100% crop of Lorie's eye:


If you overlay the crop on top of the full size image, you'll see the pixels are the same. That's the definition of a crop. It's just a portion of the full image versus a digital resizing (interpolation, the first image above) of the full image either larger or smaller.

I am having a light bulb moment Scott.

I cropped and area of a photo and that in essence creates a new picture of the original shot. It's just a way to ( zoom or resize ) an area of a shot creating a completely new picture at a magnified size. ( crap ) now I confused myself again, but I get the idea Scott.. Thanks

Where doed the % scale come into effect and why?

Gordon

[srwatters]

Originally Posted by Chief

I am having a light bulb moment Scott.

I cropped and area of a photo and that in essence creates a new picture of the original shot. It's just a way to ( zoom or resize ) an area of a shot creating a completely new picture at a magnified size. ( crap ) now I confused myself again, but I get the idea Scott.. Thanks

Where doed the % scale come into effect and why?

If you simply crop an image, there is no resizing involved. Imagine you are simply throwing away some of the image but the part of the image you are keeping is completely unchanged. Another way to think about it is if you were to frame a print and use a mat smaller than the original photograph. You effectively have 'cropped' the print using the mat. In the digital world, cropping is the same thing except you can't remove the mat and still have the original.

The only percentage that makes sense with regard to a crop is 100%. Any other percentage would indicate that the image has been resized and either pixels have been compressed (when making a smaller image) or created (when making a larger one). If you use the crop tool in Photoshop, as long as you don't put any number in the resolution box and use only the height and width controls other than pixels, you will be performing a crop on the original pixels. Any other usage of that tool will create new image data.

[bburton]

Good question; Excellent explanation and demonstration. Thanks to both of you.