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What settings for low resolution?

R Russell , Dec 23, 2009; 08:59 p.m.

I have several questions regarding placing some of my photos on several websites. I understand that image theft is something difficult to avoid, and I've read about some deterents such as using a watermark. Another suggestion I've seen is to use low resolution photos so that if your picture is stolen, it can't be printed with reasonable detail. Its the "low resolution" recommendation where I have several questions.
First, using which settings in photoshop can you actually set low resolution? Am I correct in assuming that you can only set a low resolution by changing the width and height in the Pixel Dimension area located in Photoshop's "Image Size" box? Would I also be correct in thinking that the Resolution setting in the "Document Size" box has nothing to do to with setting a low resolution for your actual photo? I believe this setting relates only to printing or web viewing, and cannot change the quality or resolution of your file. (although I've read where people on photo websites say that if you change this setting to 72, you now have a low res file).
If I'm correct in the 2 above statements, then what settings would create a low resolution file where a decent 4 X 6 print could not be made? I'm thinking possibly 600 X 400, but I'm really not sure. Finally, when saving my jpeg, what effect on resolution does the "quality setting" have on the file? If you save it at maximum of 12, are you somehow increasing the quality of the picture? Would a setting of 4 degrade the image further? Thanks for the assistance. I just want to make sure I understand all of the above.


Colin Mattson , Dec 23, 2009; 09:06 p.m.

Your understanding is entirely correct.

As far as settings that even a 4x6 couldn't be made... Good luck. Particularly depending on different people's definitions of "decent," that's a near-impossible goal unless you intend to watermark the heck out of your images or only post teeny little thumbnails. 600 or 640 in the long dimension is a fairly safe resolution.

When saving a JPEG, the quality setting affects the way the compression works. Lower quality levels will have more obvious blocking and degradation, and in most cases 4 is going to be extremely low even for looking at online.

Danny Low , Dec 24, 2009; 12:02 a.m.

Since you mention you are using Photoshop, it has a "save for web" mode which takes advantage of the fact that low resolution images often look very good on monitors, to reduce the size of the jpeg file. You can use this in addition to choosing an appropriate image size. At 300 dpi, a 4x6 print is 1200x1800 pixels. So if you do not want people to make good 4x6 prints of the images, you should reduce any images to less than 1200x1800. As 1200x1800 is a fairly high monitor resolution you can probably chose 640x480 and still have a good size image for the web. The combination of the low resolution and the "save for web" should meet your needs.


Stuart Moxham - Finland , Dec 24, 2009; 03:27 a.m.

Some people if they are downloading an image for free and printing it may even be happy to make a 6x4 inch print from a 600x400 pixel image. Simple answer is don't upload anything that you don't want people to copy or try to make prints from. You could put a copyright notice through the middle of the image so people would have to somehow remove it before printing but the most determind will still try.

Robert Johnston , Dec 25, 2009; 03:10 p.m.

Have seen some which were set to 40-50 pixels per inch in a 4x6... They looked ok when viewed at that size or smaller, not as good as an original by any means. But you can check it yourself, to see that works for you. If you attempt to increase pixel resolution to say 300 PPI, it does not improve the appearance at all.
Personally, I like Digimarc where you can imbed your copyright and all information right into the image. It can be done so it does not damage the appearance of the image. But, if you get the program to search for your images, it can turn up websites that are using them, so you can ask them to remove them. Lawsuits are expensive, but for a very reasonable price you can sue them in Small Claims court. It limits what you can get, but can cost them enough so they think more than twice about using an image which belongs to someone else.
Even if the Judge finds in your favor, then you have to collect it. Even if you cant, you can file it to hurt their credit rating so they will get denied credit until it is paid.

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