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| I just wondered what target background sky level makes for the most "natural" results? I wondered if the really experienced astrophotographers on here had a rule of thumb. I know I tend to make the background too dark by default. I guess I am asking about what pixinsight might report. 0.09 to 0.11 ? |
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There was a similar question some time ago here on AB. Unfortunately, I'm not finding the thread somehow. Personally, I am not looking for a specific sky background target value but more what gray level gives the most pleasing result. It can be a darker value or a brighter one. In total, I would say that most of my pictures have a gray level < 30/255 (which would be about 0.12). Most of them are around 22 to 25 (at 8 bit). You could simply measure the sky background from images you find there on AB and get an idea what you believe is the right one for your aesthetic expectations. CS, Björn |
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Andy, I think that this is going to end up being one of those answers that really is a personal preference. Or if your goal is to please someone, or everyone, then you would have to act toward that end. And that end will never please everyone. My personal preference is darker. Not clipped, but dark. Al Nagler used to (and maybe still does) sell his Televue eyepieces, the ones with 80+ degrees apparent field of view, as generating the experience of actually being in space. I think for me, that applies with this question. One could say that observing an object from earth, then the background should somewhat reflect the light seen by our earthbound sky. Within reason of course. Certainly no one wants to see the Manhattan sky in their astrophotos. But I can't buy that reasoning. Except for landscape astrophotos of the sky, Milky Way, etc. all our photos are significantly magnified, thereby placing us well off of the surface of our planet during our view of these objects within these images. I like the perception that we are hovering over these objects from some ideal distance that the photo shows us the "true" field of view. Of course, most such objects would still be mostly invisible, so we still need to stretch. But unless the object is behind or in front of a clearly visible IFN-like cloud of dust, even a stretched image of such would have a purely black background (this of course, not counting stars and distant galaxies). Pure space is black. Ask an astronaut. If IFN is what you want to show, having a very black background does wonders to enhance the contrast to that IFN. But I do not see the point of adding a significant gray background to an image of space that really is black. When I was in a class 1 sky last month and looked up, well, that convinced me that it is the true black of space that makes all the beauty stand out. I believe that the convention that all space images should have some distinct gray background comes from the discriminating astrophotographer/critique being able to see what all the processor did to achieve his/her results. That somehow showing your background somehow proves that you are not improperly hiding something in the depths of the darks. However, one can certainly achieve the appearance of a black space backdrop without clipping the image to zero in those areas. The other thing to consider is how the image will be viewed. If on a monitor, then one background might work well. But if printed on paper, metal or glass, then the backgrounds might all look different. Especially under different lighting. But I do not want to be critical to different approaches. I for one, appreciate the diversity of interpretation on this subject in the images posted here. However, some add the gray to such a level, as to make it appear milky throughout (almost foggy), as if there is a light leak in their imaging train. But if that is what you are striving for, then go for it. |
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When it comes to black levels, I think the best approach is to find something that works with your subject. As a subjective and qualitative guide (in my opinion): Nebulae (Small)/Galaxies: I think nebula targets that don't fill the frame typically need darker blacks to help frame them properly. Targets like Pacman Nebula, Crab Nebula, or Jellyfish require more emphasis on the object itself, so a bit more contrast with deeper background blacks goes a long way. Nebulae (Large): Nebulae that easily fill your whole frame with detail such as Orion Nebula, Carina Nebula or any targets involving IFN or faint dust benefit from brighter background. Although it reduces contrast, it maintains a huge amount of detail and more often than not, it's the entire frame that you're calling detail to anyway. Star Clusters/Spread Out targets: If you're taking photos of any star clusters or globular clusters, a nearly black background helps a lot. Stars aren't faint, so there's no need to worry about what background detail you're losing. You stand to gain more emphasis on your target, and you stand to lose nothing. Just my two cents  |
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There was a similar question some time ago here on AB. Unfortunately, I'm not finding the thread somehow. This - extended to other image properties - may be an idea to train a neural network to create IOTDs :-) Indeed there was such a thread a few months ago and if I remember well the unsurprising consensus was that in the end it's up to personal taste with the only exception that clipped pitch black is generally deemed wrong. Have fun and clear skies Wolfgang |
