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Old Jan 17, 2005, 3:04 PM   #1
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Hi, i have just had a play with photoshop cs for the first time. I have tryed cropping some images that i have taken with my d70 (highest res, 3008 *2000). I cropped an image of 1128 * 864 (when i did this i noticed the image was quite grainy, when i zoom in 2/3 times on the original image i dont notice this. I was just wondering if this usually occurs due to cropping (if i shot in raw, would this be the same?) (or could be due to iso 640?)
I have just tryed some cropping with images shot at iso 320, and they dont seem as grainy (quite abit of difference) but then again, they are different shot/different shots (wish i had images shot at the same place/lighting with different isos to test it with)
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Old Jan 17, 2005, 5:18 PM   #2
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Cropping won't make any difference in the grain of the image. Cropping ONLY removes pixels from the canvas... it does not enlarge or change the contents of the pixels that are there. Now, if you changed the resolution of the image (pixels per inch) that might make a difference. For example, if you had the resolution set at 300 ppi and clicked on the option "show print size" you might have seen a smaller, but clearer, image. But after you cropped, if you set the resolution to 72 ppi and then cliked on "show print size" you would have seen fewer pixels per inch and, at ISO 640, would have been grainy. I don't know how else your grain would have appeared unless you (1) weren't looking at the same percentage magnification when you looked at the original and the crop (2) did some sort of resize or resolution change as well as the crop.

Any consumer digitam shooting at ISO 640 will be grainy. From my experience, anything above ISO 400 on just about any digicam is almost unusuably grainy (unless that's the look you're looking for) and I wouldn't shoot on anything above 200 on a digicam. I have a digital SLR and I don't usually shoot above ISO 400 (and then I clean it up with a post processing program like Neat Image or Noise Ninja).


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Old Jan 17, 2005, 7:00 PM   #3
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If you crop an image and then view it at the same size then the resolution of the display will be lower. I'm guessing you are cropping the image to mail or post, and that resolution should look OK viewed on most screens unless you start blowing it up. If you zoom in on an 1128 X 864 image you get to the point where you are seeing pixels and probably noise. There isn't anything unusual there. If you want to zoom in or print a large print don't downsample the image to a lower pixel count. It makes sense you can't blow up a 1Mp image as much as you can a 6Mp image.

One of the reasons people get DSLRs is so they can shoot at higher ISO without the noise being a big problem. Your D70 should be fine at ISO800 if you don't want to go reducing the image size and then blowing that up.

Neat Image Pro works as a Photoshop plug-in and really does a nice job reducing noise without degrading the resolution. You might try the free trial stand-alone version to see if it is worth getting.

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Old Jan 18, 2005, 2:27 AM   #4
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Ok thanks for the input, i tryed neat image (just had a quick go on auto filter and it worked great, the grainyness was gone!!) although i dont have time to play with the settings now, ill come back later and try the manual settings
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