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Photo resolution

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designbr

Technical User
Mar 29, 2005
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Just a simple question. Sometimes when I have to fix photos the resolution is so bad that anything I do doesn't help like pixels, dpi, etc. All photos can be fixed or there are those ones that are simply trash?? I received a bunch of them to work on last week but when I try to zoom you can see the horrible square pixels no matter what you do. The point is that I'm afraid to return with no picture fixed because seems that I did nothing or I am complaining about the camera or the photographer. Those pictures are intended to be used for web and printing (larger and smaller sizes) so have to be fine on 72 or 300dpi. I am working on a PC and with Photoshop CS.
 
If you are working on images for screen then the physical dimensions in pixels is what matters.

e.g. A 400px x 350px image will be 400px x 350px whether it's "resolution" is 10ppi or 1000ppi.

Also, if you zoom in enough on any image then you will see it's pixels. It's what images are made of.

You may be seeing JPEG artifacts, a result of the compression process employed by JPEGing an image too much or too many times.

Certainly some images are poor quality and one has to ask whether it's worth trying to fix them or just find another image.

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One trick you can try is to vastly increase the resolution and decrease the size - for print.

If you get something from a digital camera that's 2400 X 1800 pixels with a coresponding print size, but 72 dpi, you can usually up the thing to something like 600-1200 dpi and reduce the size to someting like 6 in X 4 in.

PS will do some interpolating (sort of add dots) when you boost the resolution but it will look really bad unless you can reduce the physical size of the pic.

If you get small, lousy 72 dpi pics you can try playing in gaussian blur to cover things up a bit, but most of the time it's best to try to get a replacement.

One thing to remember is to NEVER work on the jpeg. Save the image as a .psd and work from that. Every time a jpeg is saved the quality is reduced. If you don't select the highest quality setting when saving a jpeg the quality loss is even more.
 
There' s also a handy plugin called genuine fractals I've used when I had to enlarge a bit - does a better job interpolating the PS standalone.
 
>>PS will do some interpolating (sort of add dots) <<

It's not really a 'sort of' adding dots - it really does add pixels, by sampling the colours of the nearest neighbours (which neighbours are decided by the interpolation method) and is never really a good idea. In continuous tone photos, PS 'guesses' at what colour those added pixels should be usually end up making the photo blurry, unless very small upsampling is done (few percent).

Clicking OFF the resmaple box is the best approach to start with. In your example, if you are given an image measuring 2400 X 1800 pixels (which would measure 33.3" x 25" at 72 dpi) and you go to Image>Image Size and enter '300' in the resolution box - leaving the 'resample image' box unchecked - then you end up with a very respectable 8" x 6" image at 300 dpi. This sort of resolution would only be necessary for commercial printing. For desktop printing you could probably use 200 dpi - which would allow for a 12" x 9" print.

>>All photos can be fixed or there are those ones that are simply trash?? <<

There are definitely ones that are simply trash and no amount of editing can help> If there are insufficient pixels to begin with - where are you going to get ones that are the correct colour - and in the right position? Better not to waste your time if the pixel dimensions are small to start with.
 
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