UFRAW vs RawTherapee

I’ve recently made the switch from ufraw to rawtherapee. I wish I hadn’t waited so long. OpenSource software is such a blessing.

However I am curious about a few random details. In ufraw I primarily manipulated “exposure compensation gamma and linearity” before sending those results (as a tif?) to Gimp.

Ufraw and RawTherapee both have an exposure compensation slider that appear to do the same thing.

Punchline Question:
What menus on RawTherapee correspond to the gamma and linearity sliders in ufraw? Highlight Compression in RawTherapee seems related to gamma, but not…exactly the same.

Highlight Compression in RawTherapee is really useful for high constrast wildlife closeups taken in harsh midday sun, by the way.

I used to use ufraw exclusively but I didn’t play with gamma settings. Shadow / Highlight manipulation should be done with the 2nd curve panel and the exposure slider if needed. The first curve panel as I understand it is slightly different and can also be used. It applies a curve to the raw data before much has been done to it. An idea borrowed from Nikon. Actually people can have problems getting the Nikon look on photo’s without it and always use NX2 for raw development to get round the problem. I gave up on a D7000 because of this problem. One thing people should be able to do is obtain the colour and gradation of camera jpg’s pretty easily. I found that a mixed bag even with the correct style of curve being available in ufraw.

Some time before this I did play with gamma. On this package it was represented by a curve - a straight line at 45 degrees representing a gamma of 2.2. The sRGB standard. I found that very slight tweaks at the centre made a difference. What this was doing in practice was just adjusting mid tone contrast. That can be done with ordinary curves too orthe centre slider in levels that is available in packages such as the GIMP.

RT’s shadow and highlight manipulations are using variations on luminosity masks. Google will tell you what those are.

RT does have a facility for adjusting gamma but in general it should be left as it is.

Trying to explain curves on a web posting is rather difficult. Youtube search GIMP curves brings up some explanations that aren’t too bad but none as far as I am aware mention that the slope of the curve in some region of the tonal range sets the contrast in that area. Steeper = more contrast, less steep = less contrast in that region. The axis of the “graph” represent the entire tonal range of the shot. One axis input and one output.

:hushed: Personally I think RT should have the same style of levels as the GIMP has including the additional slider that sets where the output tonal range will be placed. True the same thing can be done with curves but it’s far more easier to use and quicker. RT’s curves aren’t too good anyway. The smoothing algorithm they use is too severe and goes unstable which means that creating abrupt changes in a specific tonal range is likely to be unsuccessful.

John

Thank you. This was useful

You may find this short guide useful:

Yes I do use the tone curves when processing. I think I understand the 255 tone value slot concept too, and how mouse-dragging the left and right menu markers closer to the central portions of the curve–that actually have pixel values–is roughly equivalent to stretching the tone curve outward, as if there were dark values at menu left and lighter ones at menu right.

The question I still have is about the difference–if indeed there is any difference–between manipulating tone curves in a raw editor like RawTherapee and manipulating them later, after the raw image has been converted to tif and sent off to Gimp. Is there a difference? Isn’t manipulating tone curves in here the same as manipulating them there?

While you’re working in raw, you generally have more lattitide to work with; you can push your edits a bit further without getting gaps in your histogram.

If the image data is the same, then there can at least be a common playing field. If the raw editor uses 16-bit unsigned integers for its R, G, and B channels, that data can be saved essentially unchanged to a TIFF. If that TIFF can be opened “intact”, that is, without down-sampling to 8-bit (pre-2.9 GIMP did this), then image can continue to be edited on common terms, so to speak.

Now, curve tools vary a bit in their “curve-ness”. All use some sort of spline algorithm to plot the curve through the control points, and there are a variety of those, and they don’t all behave similarly in plotting a curve through the same points So, for the same control points, no two curve tools usually yield the same transfer function.

I think one exception would be a so-called “linear curve”, where the function between the two end control points is a straight line. I think most curve tools would yield the same transfer function in this case. Most notions of brightness and contrast are linear curves.

Soooo… there are the differences and similarities I can think of.

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Not really. With the exception of the first unusual curve in ufraw they are all the same. One axis represents input and one output. It doesn’t matter in that respect if the input is 8bit,16bit or what ever. Where they are likely to vary is in the area of the format used to save them and the “damping factor” used to smooth the curve as points are added and the shape of the curve is changed. RT seems to have improved of late or maybe I have not tried it on photo’s that cause the problem. The catch with curves is that contrast is changed at the expense of contrast in other tonal ranges. Take a typical S curve for instance. It reduces contrast at some point at the dark end and also at some point at the highlight end. Contrast between the points will be increased. Some shots have very little tonal range in some areas of the histogram. The curve can be “flat” in that area allowing more contrast to be added elsewhere.

Personally I feel all packages should have GIMP style levels included. An exact copy of the controls it offers. The same thing can be done with curves but for initial adjustments of a shot it’s a lot quicker and for some easier to use as well. The problem with curves really is that in some areas tiny adjustments can make rather a lot of difference that sort of thing is better handled with sliders or pop up curves such as the GIMP and Fotoxx use that can be enlarged to what ever size some one needs. The sliders can be too. Curves - well go to certain pay for packages and there will be sliders there as well as usually offering levels as a specific option.

GIMP currently has the problem that it works in 8 bit or maybe the latest version can handle more. This will put some restraints on how far images can be adjusted before banding appears. The real problem though is not that. It’s rounding errors when things are manipulated - information is lost and can’t be brought back so best do a particular adjustment once not keep going back and changing your mind by applying the same adjustment again. In other words it’s more or less fine for people who have a lot of experience in using it. They will manipulate a raw image using say ufraw at a greater bit depth allowing them to fiddle around and exit that to 8 bit with a pretty clear idea what they are going to do with it and how far things can be taken before 8 bit becomes a problem. Personally I mostly use it for layer work also brushes and masks etc plus some of the plugins. There are plenty of video’s about that show how all sorts of things can be done with it. :grinning: I used nothing else for improving compact jpg’s for years. A period when I didn’t want to carry a dslr about. These days I often use RT in much the same way as Ufraw can be used, Just simple adjustment and then switch to Fotoxx and maybe the GIMP or maybe both.

I tried DarkTable last night though and may switch. I gave it a problematic raw and it made a pretty decent job of converting it. It used a sensible initial curve. Not sure if that is a default or automated. The simple adjustments allowed that to be cleaned up. Then had a play with drawable masks. Due to doc’s there was a certain amount of suck it and see to get some idea what the controls did. There may be some detailed tutorials about that can help with that. However given that feature it is probably the only single package that is capable or doing most things people are likely to want other than Fotoxx which actually can do more. Fotoxx defaults to using RT for raw development. It makes heavy use of layers for various things under the hood but that aspect is hidden. It can also do selective drawn masks but there can be the usual problem of leaving white lines around modified areas as there can be on some GIMP plugins. Many people use free hand drawn masks to get round that aspect. The blend on GIMP brushes is excellent making that process a lot quicker than people may think.

John

Thank you. Good discussion. My picture view is getting bigger. I love
photo processing. I’m so old I remember the black and white darkroom. RT
and Gimp et al are so much better. And more colorful.

The problem with the GIMP really is the mechanism it uses to make changes not the fact that it works in 8 bit. As a for instance say a luminosity mask is generated - easy enough to do but once it’s done it’s done. Then a blur might be needed - easy again but once it’s done it done and that’s it. For some reason it’s remained like that for a long long time. What it needs to do is apply the changes in stages and remember the settings so that some one can go back later and change them if needed. I’ve always thought that it would probably be possible to add this to the way it currently works. The history stack just saves image states and changes but not settings.

The other problem in places is lack of a full screen preview. That probably dates back to IBM PC issue one using an 8086. There are good reasons for limiting preview size, speed for one but curiously when adjusting images for over all look there is a maximum size that can be handled at the usual monitor viewing distances. That could be used instead.

Blur is a real pain in the posterior in this area. One work around is to duplicate the layer that is going to be blurred. Blur one of them and try it, No good - same again using the duplicated layer and so on. 0r repeat via the history stack.

:rofl: I sometimes think this sort of thing is an OS problem. People tend to want to work where they think the action is - more and more plugins and filters etc. When some one sets out on a fresh software project they need a pretty clear idea of where it’s heading. Lacking that can mean a significant amount of work to change pretty basic functionality aspects so the changes never happen. Taking GIMP as an example both it and PS were initially mostly aimed at graphics artists. PS moved on GIMP in this respect hasn’t really. I believe there have been some attempted spin off’s but they never seem to go anywhere. I have read that this is due to the GIMP mafia. There is no such animal really as people come and go.

John

Some remedies which can be combined:

  1. Choose control cage type curve and if necessary right click control points to set it precisely
  2. Use multiple curves (2 in exposure section, 1 in Lab), e.g. one for highlights, one for shadows, one for a specific section in tonal range
  3. Do all edits you can do at one time > save 16 bit tiff > reopen it in RT and re-edit > repeat if necessary
  4. Save two or more versions (use 16 bit tiff) of the shot and blend them in Gimp

Stable Gimp 2.8.* is limited to 8 bit. Unstable Gimp 2.9.* allows you to edit higher bit depth images and I have been using it more than 2 years. It is fine. Just edit the shot in RT > save 16 bit tiff > open it in Gimp and convert to 32 bit floating point

Agreed, editing is destructive. You cannot re-edit for example a tone curve after you have clicked “ok”. You can save the curve, but you still have to plan well ahead what you are going to do and in which order. Merging must be also carefully planned. Adjustment layers are mentioned in the Gimp Roadmap, 3.2 is the version (3.1 unstable)…

https://wiki.gimp.org/wiki/Roadmap

Straight curves as per the ones I discussed always increase contrast in one tone area at the expense of another area no matter how many times they are applied. They don’t miraculously increase the tonal range capabilities of the output device.

There are ways around the problem but they always involve some method of only applying the changes to a specific area of the shot some how or the other. That has the catch that there must be room in the histogram that allows the change. Take clouds for instance. Ideally some one might want to increase the contrast. If that is done by brightening there must be room at the high end of the histogram to allow that to happen. Often this can be done in the opposite direction, in other words darkening darker areas smoothly up to peak white or near to it. Blending what are effectively multiple exposures some how is usually the best solution really. Sort of HDR approach in an odd sort of way - getting say 9 stops into the say 6 available in a jpg is hdr like really.

Using “say” because there is some conjecture about how many stops there actually in are in a raw file. Jpg’s too.

Yet another way that is often simpler is enough use of shadow and or highlight compression to allow the contrast increases at either end to be applied. That assumes that the middle tonal range can be kept as it should be or adjusted on it’s own some how.

The really sick thing about pp though is people need a monitor that perform to a decent level. Lots out their don’t. Another aspect that should ideally be thought about during pp. That can make the job a lot harder so assuming a decent monitor at the other end is often taken as a fact in photo circles.

John

Yes to this! I really love the GIMP levels tool. It’s to my mind the most intuitive implementation of this around in the FOSS world. Showing the histogram move in real time is the key, enablinf to move the darks, lights, and midtones on one slider. For me, this is the best. I wish Darktable, etc., could implement their sliders in the same way.

Have you tried darktable’s zone system module? It works sort of like levels, but with more control and a nice tonal preview.

GIMP levels will do more than most can. Auto for instance will attempt to correct the colour channels as well as luminosity. Sometimes it works sometimes it’s a disaster but under circumstances where this is needed it may give people a clue. It can be used on any colour channel. Being able to set the output range is very useful especially as mid tone contrast can be tweaked at the same time. It can allow highlights to be reduced leaving room for further enhancements. Dark end same. This can all be done with curves but the problem there is that tiny adjustments can make a rather large difference. Sliders make more sense given that type of problem. I can do the same thing with curves and do but find it much easier if I can enlarge the curve view as much as I need to.

There are other situations where it can help. I’m reminded of a photo of a Turkish belly dancer I took under extremely mixed lighting, several different colours. I managed to get whites etc correct easily but wasn’t happy with the skin tones. Some one with way more experience than I have made a minor adjustment to the red channel curve and suddenly the entire shot was ok While levels may not have been able to do the same thing it would have been a much quicker method of seeing where the problem was. Experienced - he does it for a living.

As mentioned pay for packages usually have sliders in the curve panel and the above outlines why. They are tricky things to adjust by moving points and it’s all in one place. Personally I would prefer the GIMP arrangement. More sophisticated levels and separate curves.

John

@paperdigits Yes! I do like the zone system (it’s also central to Lightzone, which I dabbled with a bit last year). I agree that it’s probably the closest one can get to a GIMP style levels tool in DT, but I still find that GIMP levels more intuitive. I DO like the zone “map” that shows up with those zone tool, but in terms of the actual adjustments, it’s all about that GIMP style integrated histogram for me.