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JPEG woes
- Thread starter RichardC
- Start date
Thanks Welles.....After I finish editing my ,psd file I flatten it and ?save as? a .tif and put it on a CD to send out for printing. Most are 8x10 inches at 400 ppi.....around 36M......4000 x 3200 pix.
I usually save a JPEG for email that has the width reduced to 800 pix and the file size drops to a little less than 1.5M. The JPEG box usually allows me to compress it to 50/100K in the ?medium? range.
Sometimes the jpeg at medium range reads around 500K and all the way to zero only takes it down to around 200K......that?s my problem. It just happens at random times but not very often.
I haven?t noticed any obvious color concentration differences in these pics. I've never "saved to web".......
.....RC
I usually save a JPEG for email that has the width reduced to 800 pix and the file size drops to a little less than 1.5M. The JPEG box usually allows me to compress it to 50/100K in the ?medium? range.
Sometimes the jpeg at medium range reads around 500K and all the way to zero only takes it down to around 200K......that?s my problem. It just happens at random times but not very often.
I haven?t noticed any obvious color concentration differences in these pics. I've never "saved to web".......
.....RCRichardC,
May I suggest, if you have PS 7 or CS that you give Save For Web a try. Among other things you have a view of the original with three other views a possibility. With it you can look at the output image prior to saving it. Peculiarly, Save As... and choosing JPEG and Save For Web in the JPEG format give different results. A couple of years back I did a serious test with Boxtop Software's ProJPEG (a PS plugin for Macs), Save As..., and Save For Web. Until PS7 ProJPEG was the JPEG compression winner by far. My test was to take an image a save it to JPEG matching the file sizes of the resulting compression schemes as closely as possible and then look closely at the various artifacting present in the results. My impression consistently was that Save For Web... was the best compression algorithm of the three by a considerable margin.
Good Luck!
May I suggest, if you have PS 7 or CS that you give Save For Web a try. Among other things you have a view of the original with three other views a possibility. With it you can look at the output image prior to saving it. Peculiarly, Save As... and choosing JPEG and Save For Web in the JPEG format give different results. A couple of years back I did a serious test with Boxtop Software's ProJPEG (a PS plugin for Macs), Save As..., and Save For Web. Until PS7 ProJPEG was the JPEG compression winner by far. My test was to take an image a save it to JPEG matching the file sizes of the resulting compression schemes as closely as possible and then look closely at the various artifacting present in the results. My impression consistently was that Save For Web... was the best compression algorithm of the three by a considerable margin.
Good Luck!
Simply put, jpg compresses by taking every pixel, one by one, then looks at the pixels around that pixel and tries to calculate an average value. (really scientific attitude: forget about all those extra digits: 3,14 is enough to work with. The rest can be discarded ).
So when you have, say, a sky, all pixels will slowly vary. This, jpg can easily cope with. (ie: laboratory conditions)
If your image is very dense, has many small shapes in lots of different colours, then there is much less possibility to simplify things. Which makes the jpg file much larger. (ie: real life situation)
What you can do to reduce file size (as it is clearly the tiff that is needed, and the jpg is only for giving an idea) is to blur a little. This can work miracles sometimes.
In any case, do as Welles said and use Save for Web. Much better indeed.
So when you have, say, a sky, all pixels will slowly vary. This, jpg can easily cope with. (ie: laboratory conditions)
If your image is very dense, has many small shapes in lots of different colours, then there is much less possibility to simplify things. Which makes the jpg file much larger. (ie: real life situation)
What you can do to reduce file size (as it is clearly the tiff that is needed, and the jpg is only for giving an idea) is to blur a little. This can work miracles sometimes.
In any case, do as Welles said and use Save for Web. Much better indeed.
[excited] Thank you guys! "Save for web" is certainly the winner. I could get it way down to 60K as opposed to 500K in "Save AS" and it doesn't look that bad! I have PS 6.1 and it's got "save for web" but I've never used it....scared that it might take me to uncharted territory
Thanks again..... You've been a great help!........RC
Thanks again..... You've been a great help!........RC
one more point
hey, richard. when you reduce image size, you usually need to sharpen it when it's in the smaller size. i've found that this does the trick: go to unsharp mask. enter 25 percent amount, then set a 1 pixel radius, and set levels in threshold to 1-3. i hope this helps. good luck, boyd.
hey, richard. when you reduce image size, you usually need to sharpen it when it's in the smaller size. i've found that this does the trick: go to unsharp mask. enter 25 percent amount, then set a 1 pixel radius, and set levels in threshold to 1-3. i hope this helps. good luck, boyd.
I know the feeling Richard. You know when I have this problem most?
When I make textures in Photoshop. Adding clouds, noise and applying lots of filters seems to make these image difficult to compress.
And something else; when I have to compress these files with a quality factor of let's say 40-50% (otherwise they're too big to post on a board) I also notice that it has quite a negative effect on the colors! (I have examples). I have to admit though, this loss of colors is less noticeable in photographs but it's still there.
When I make textures in Photoshop. Adding clouds, noise and applying lots of filters seems to make these image difficult to compress.
And something else; when I have to compress these files with a quality factor of let's say 40-50% (otherwise they're too big to post on a board) I also notice that it has quite a negative effect on the colors! (I have examples). I have to admit though, this loss of colors is less noticeable in photographs but it's still there.
That's also because jpeg cuts the problem in two. The designers/inventors of this compression method took for granted the average case that human eyes are less sensitive to a change in hue than in brightness.
In some (real world) cases, this proves to be what it is: a mean value, and average, a simplification.
Hence visible loss in hue.
In some (real world) cases, this proves to be what it is: a mean value, and average, a simplification.
Hence visible loss in hue.
It sounds like you guys are talking about a subtle color change? I was having major unwanted color changes when I emailed a jpg or ?saved for web? but it may be just a quirk with my iMac & PS6. After hours of trial & error and blind clicking I came up with a fix: 1st I change the document profile to ?Generic RGB Profile?. Then I ?Save for web? and when that screen comes up I check the ?ICC Profile? box up in the right top. Then further up at the top there?s a arrow that opens a sub menu. I check ?Use Document Color Profile?. That seems to fix it.
Also, thanks boydphoto for the tips!
Cheers........RC
Also, thanks boydphoto for the tips!
Cheers........RC
Yes, but that are two different things Richard. I'm really talking here about color changes caused by Jpeg and the compression rate. Compress at 100% and you won't see any visual difference, but increase the compression (by lowering the quality) and you'll notice what Erik and I are talking about.RichardC said:
What you're talking about is something totally different. That is a color management issue.
I do know from experience (I hang out a lot in a photography forum) that I always need to set my color settings to Web Default and sRGB to see on the web exactly what I see in Photoshop.RichardC said:
Maybe that's the way to do it too Richard and then you might (because I'm not sure because I have XP) have to change the setting in the web preview to Standard Macintosh Color.
