RAW question

[JPS]

PSE9....

[ajohnw]

All I can do on these is watch video's. Out of interest really to see how the other half live. I believe I mentioned all raw dev software is very similar in relationship to curves. Seems the tutorials I have seen don't want to use them. At least the video's I linked too do give a decent demo of what certain types do.

If anyone does try rawtherapee there are 2 main curves. I thought but hadn't checked that the 1st would be applied to raw data after exposure and white balance and the 2nd is intended for pure luminance control. The thought related to Nikon raw where a curve is embedded in the file. Not sure if this is a current Nikon feature but will be finding out shortly.

http://ufraw.sourceforge.net/Guide.html

John
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[Manfred M]

All I can do on these is watch video's. Out of interest really to see how the other half live. I believe I mentioned all raw dev software is very similar in relationship to curves. Seems the tutorials I have seen don't want to use them. At least the video's I linked too do give a decent demo of what certain types do.

If anyone does try rawtherapee there are 2 main curves. I thought but hadn't checked that the 1st would be applied to raw data after exposure and white balance and the 2nd is intended for pure luminance control. The thought related to Nikon raw where a curve is embedded in the file. Not sure if this is a current Nikon feature but will be finding out shortly.

http://ufraw.sourceforge.net/Guide.html

John
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Not sure why people don't like the curves. I find that I use them pretty well all the time; they are a far better way to play with the image contrast than some of the other controls that are available. That being said; you can get some pretty awful results if you don't understand how curves works.

[Rita]

Rita,

Considering that you are new to using RAW files, it might be helpful to clarify the term, "convert," mentioned in Dan's post and other posts in the thread. Though a RAW file can be converted to a different file format as he explains, to display the image of a RAW file without changing to a different file format is also called converting a RAW file. In that case, the conversion is from RAW data to image data. That explains why ACR and other software that allows us to display the image of a RAW file and to alter it without converting to another file format are called RAW converters.

Thank you Mike. I was wondering about that but wasn't sure how to word the question. Most helpful.

[Mike Buckley]

Not sure why people don't like the curves. I find that I use them pretty well all the time; they are a far better way to play with the image contrast than some of the other controls that are available. That being said; you can get some pretty awful results if you don't understand how curves works.

Completely agreed with every detail.

[ajohnw]

I find them very useful on jpg's as well.

John
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[Richard Lundberg]

Most if not all the non Adobe RAW converters use dcraw as their baseline software, so when you buy them you're getting the same thing with slight modifications.
Curves is just changing the gamma correction, usually for mid tones. Adjustments in RAW for clarity, vibrance, saturation, contrast, exposure, white balance, temperature, and tint offer a wide range of effects to customize your image. Not all RAW converters offer lens and perspective correction, but the better ones can give you much improved images. ACR, ACDSee, Lightroom, PhotoNinja, DxO, Capture One are excellent. PSE has ACR as well. Aoerture does not have lens and perspective. I'm not sure about Gimp. There are lots of apps that will open RAW. All of these apps have at least one problem, from UI to omissions to save capability. You may have to use two or more to get what you want. The ability to work on tiffs and jpgs and use almost all the tools is very useful to save otherwise very flawed images.

[ajohnw]

The curves I am refering to Richard, and I suspect others as well control luminance levels across the range of luminescences that are possible. By varying the slope this effectively controls contrast. Not easy to put into words but the bottom scale show full black to full white. The default line is at 45 degrees. Lift up the left end and it will brighten dark colours, pull down the right end and it darken bright colours. Play with the middle and it will adjust mid tones and etc all along the line. Some packages have similar curves for each colour and curves in LAB space. Nothing to do with gamma. That can be adjusted in some packages with a different curve.

As Manfred pointed out they can produce some rather strange results and it takes a bit of practice to realise what can realistically be done with them. It is possible to use them in a very extreme fashion at the dark end but it's not the easiest thing to do. They are at there best when used to perfect a decent exposure. The mid tone etc sllders are just doing the same thing. Where sliders can be useful is marginal corrections to the black level as shifting the bottom left end of the curve inwards may be a bit coarse. Another vaguely similar control is often referred to as levels. Many curves users don't like levels and visa versa. Autolevel can be useful to all but sometimes isn't a good idea. It will basically stretch the histogram for you and also as I understand it pick a mid grey level for you as well.

There is a demo of moderate use of curves on this using a very dated version of rawtherapee. There is also another purely on curves somewhere. Can't remember which package. I have used it in the GIMP to fix darker areas in jpg's from compacts for rather a log time. Best way to learn is to play with it. There is usually some way of setting it back to a straight line or removing adjustment points that have been added.

http://www.youtube.com/watch?v=1c3c33JVKVE

John
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[Richard Lundberg]

It's gamma .

[ajohnw]

Richard perhaps some one should contact several packages producers and ask as a for instance why the have 2 tone curves, a luminance curve and gamma adjustments as well and why the gamma doesn't change when the curves are used. Gamma is a process applied to make colours better when they are displayed. Jointly cooked up by Microsoft and Hewlett Packard but probably mostly by the later to improve the look of sRGB images. The curves mentioned work on RGB. sRGB and it's gamma are an output profille for a screen or some printers. There are other output profiles such as the one Apple used and others for printers as well even for different types of paper.

John
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[Glenn NK]

Not sure why people don't like the curves. I find that I use them pretty well all the time; they are a far better way to play with the image contrast than some of the other controls that are available. That being said; you can get some pretty awful results if you don't understand how curves works.

How true.

[Richard Lundberg]

Luminance is the result of gamma. When you use curves you are making an incremental change to gamma in one area of the response curve. Adjusting gamma in levels is changing the curve itself. Various devices have various gammas. Older Macs used 1.8 gamma correction because it matched print better. I still use it for printing to inkjet. Pro Photo uses 1.8 for that reason.