steve72614 wrote:Hi Ivo,
Develop help buttons do not work on Windows 7 with Star Tools version 1.3.5.289.
The same Star Tools version does not have this problem with Windows 8.1.
Hmmmm... This is really most bizarre
I can't replicate this one for the life of me on the 64-bit Windows 7 machine I have here.
Does a fresh 1.3.5 copy help?
I see that Gamma is typically set a little above 2.
I am using an unmodified DSLR, convert to tiff with dcraw -r 1 1 1 1 1 etc, DSS, then ST.
Should I be using a default Gamma in Develop besides 1.0?
Target viewing is on standard computer monitors.
Monitors (and a lot of other media) expect a non-linear transformation of linear brightness intensities (the latter being the rough photon counts your sensor caught) of (roughly) gamma 1.9 - 2.2, depending on the profile (most use the sRGB profile for which 2.2 is appropriate). What this means in practice is simply, that when stretching in StarTools, when it "looks good" on your monitor, you're done! A simple 2.2. gamma correction often (mostly) doesn't fly for astrophotoigraphical data (as it is often very faint) and you'll want to stretch much more.
Why not start with a gamma correction straight out of the gate (e.g. before passing the data to StarTools)? This is because some operations absolutely require linear data as input (e.g. deconvolution, color calibration, etc.).
[/quote]
My ST process is AutoDev, Wipe, then Develop, then other stuff.
I find that I get too much noise if I do a second AutoDev.
I'm in the suburbs, but a friend with darker skies reports the same thing.
I would benefit by any extra info on how to use Develop, especially the Gamma setting.
Hi Steve,
With regards to the AutoDev functionality, does the following information (from the website) help?
Usage
^
Great allocation of dynamic range by AutoDev after taking care of the stacking artifacts, gradients and light pollution using the Wipe module.
AutoDev has a lot of smarts behind it. It analyses a Region of Interest ("RoI") - by default the whole image - so that it can find the optimum histogram transformation curve based on what it sees. The 'Develop' module by comparison, is more simple in that it mimics photographic film development, which doesn't actually take into account
what is in the image.
Understanding AutoDev is pretty simple really; its job is to look at what's in your image and to make sure as much as possible is visible. The problem with a histogram transformation curve (aka 'global stretch') is that it affects all pixels in the image. So, what works in one area (bringing out detail in the background), may not necessarily work in another (for example, it may make a medium-brightness DSO core harder to see). Therefore stretching the image is always a compromise. AutoDev finds the best compromise global curve, given what detail is visible in your image and your preferences. Of course, fortunately we have other tools like the Contrast and HDR modules to 'rescue'
all detail by optimising for local dynamic range on top of global dynamic range.
The latter is a really useful feature, as it is
also very adept at finding artefacts or stuff in your image that is
not real detail but requires attention. That's why AutoDev is also extremely useful to launch as the first thing after loading an image to see what - if any - issues need addressing before proceeding. If there are any, AutoDev will show them to you guaranteed.
After fixing such issues, we can start using AutoDev's skills for showing the remaining (this time
real celestial) detail in the image.
If most of the image consists of a background and just a small object of interest, by default AutoDev will weigh the importance of the background higher (since it covers a much larger part of the image vs the object); given what it has to work with, it is the best compromise. If the background is noisy, it will start digging out the noise, mistaking it for fine detail. If this behaviour is undesirable, there are a couple of things you can do in AutoDev.
- Change the 'Ignore Detail < parameter', so that AutoDev will no longer detect fine detail (such as noise grain).
- Simply tell it what it should focus on instead by specifying an ROI and not regard the area outside the ROI just a little bit ('Outside ROI influence').
You'll find that, as you include more background around the object, AutoDev, as expected, starts to optimise more and more for the background and less for the object; it's doing its job very well!
So, to use the ROI effectively, give it a 'sample' of the important bit of the image. This can be a whole object, or it can be just a slice of the object that is a good representation of what's going on in the object in terms of detail, for example a slice of a galaxy from the core, through the dust lanes, to the faint outer arms.
There is no shame in trying a few different ROIs in order to find one you're happy with. What ever the case, it certainly beats pulling histogram curves, both in results and objectivity (you've got a dedicated algorithm/assistant watching over your shoulder!).
