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  #1  
Old 05-31-2007, 12:13 AM
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branley branley is offline
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Default Compression problems

I've recently started using RAW and I've come across somethings I can't rectify. when I take my image into Nikon capture it looks great, then I turn it into a JPEG at 300 res and take into Photoshop CS2 it doesn't look so good, the colours aren't so rich. Even worse than that, when I duplicate the image and reduce it to 72 res for posting it looks like it's over sharpened (the classic look of straight lines having jagged edges) and at this stage I haven't sharpened either image. I've been wanting to post for 4 or 5 days and it's just driving me to distraction. Any advice would be gratefully accepted.

Stephen
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Old 05-31-2007, 12:36 AM
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Default Re: Compression problems

Hi Stephen
I work my image in CS2 in the raw mode,and do all my work in this state.
I transfert to JPEG at the very end when I save my image,after sharpening.
I reduce the image to 72 just before sharpening.
The drawback is a little slowness and a need for a large memory.
Hope this help.

Charles
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Old 05-31-2007, 11:10 AM
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Default Re: Compression problems

Your "300 res" and 72 res" are presumably dots per inch. They matter for printing, but have no influence on the actual resolution of the electronic file: only the size in pixels is what matters. Dots per inch are meaningless for images shown online - only pixel size matters.

Try importing in Photoshop at full size if it supports NEF, otherwise export from Nikon capture at full size as TIFF, not JPEG: that way you don't lose any information at the first step.

If your colors look different in PS, that's probably a matter of color profile - check what you have in your original, and whether PS is converting that, or interpreting it as something else.

Finally, when you reduce the size of the image (pixel size) for publication and you see jagged lines, try reducing it stepwise (without saving in-between); use a percentage that doesn't create exactly half or quarter size, so interpolation is required. Also check what type of resampling is used - different resampling methods can have very different results. Experiment! If the original is very large, you could make one or two large steps first, then work towards the intended size in steps of 90%, switching to pixelsize only as the last step. In some cases (though not all) this can actually have a sharpening effect.

Use any sharpening only as the last step before finally saving as JPEG.
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Old 05-31-2007, 11:50 AM
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branley branley is offline
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Default Re: Compression problems

Thank you Charles, good of you to take the time to help me out.

Regards

Stephen
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Old 05-31-2007, 10:33 PM
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Default Re: Compression problems

Hi Marjolein, I appreciate your advice, I'll give it a go, thank you, it's much appreciated.

Kind regards

Stephen
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Old 06-01-2007, 01:48 AM
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Default Re: Compression problems

Hi Branley
I also have the same problem.
But i don't find the solution.
I try many PP but it's always the same.
I ask me if it depend on the speed of the connexion.
maybe the picture is damaged if download in low speed (i don't have adsl)
Do you have any idea ?

bertrand
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Old 06-02-2007, 01:14 PM
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Default Re: Compression problems

Salut Bertrand,

It's not the connection speed as I have broadband. I have tried to reduce the size of the RAW file to 800px before converting to jpeg and it is a little better but not perfect. I will keep looking for the answer, if I find it I will email you my friend.

Amicalement

Stephen
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Old 06-02-2007, 06:09 PM
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Default Re: Compression problems

Hi Stephen, I was wondering why you hadn't posted for a while.

Here's what I do with my raw images:

In Nikon Capture I usually start off by using the D-lighting to lift the shadow areas. I nearly always under-expose my shots to retain highlight detail, so it's often necessary to brighten areas of shadow at this stage.
I then use curves to add a bit of contrast and punch to the image, a shallow S-curve usually works best, but be careful not to overdo it.
That's about it, although I'll sometimes adjust the colour and dark tones slightly in the photo effects box.
When I've finished in Capture I save as a TIFF file, not JPEG.

In photoshop elements, I do some minor exposure adjustements if necessary - levels, darkening highlights, contrast etc. Sometimes I'll adjust hue and saturaion slightly, if the image needs it, then clone out any dust spots that have managed to creep in.
Then it's time to resize the image, and apply a bit of sharpening. Sharpening is always the last step in the process, and I only apply it to those areas of the image that need it - there's no need to sharpen areas of smooth tone such as skies, and of course areas of an image that are supposed to be out of focus shouldn't be sharpened either.
If the image is going to be posted here, I use the save for web option, which excludes the shooting data, devoting the max 200kb to the image itself.

I hope this is of some use.

Cheers,
Ben
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Old 06-02-2007, 07:17 PM
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Default Re: Compression problems

Hi Stephen,

You've already been given some very good advice by Charles and Ben. I've found a similar problem when exporting to CS2, not just with RAW conversion in Nikon Capture NX but also Capture One. But I don't think the problem lies with the RAW coverter but with CS2. I've read that a lot of artefacting and other problems arise in CS2 (and perhaps other PS programs) if the image is viewed at any magnification other than a multiple of 25 (i.e. 25%, 50% etc). The default viewing for my D200 files in CS2 is 16.6% and, indeed, a lot of straight lines look jagged at that magnification. But, when uploaded (usually to Flickr), the problem disappears again. Hope this reassures you that it is a minor software problem and not a problem with your technique.

Look forward to seeing more posts from you soon.

Best wishes

Stephen
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Old 06-03-2007, 05:09 PM
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Default Re: Compression problems

I hope this will get me around the problem Ben, as I'm fast running out of ideas. I have tried coming out of capture in TIFF and converting to JPEG at the end, I've also tried reducing the RAW file in size before converting to JPEG but neither seems to have worked but as Stephen said, perhaps the problem will disappear when uploaded. Thanks again mate and I hope you're having a good Sunday.

Regards

Stephen
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