RBA's Astrophotography

Sleepy astrophotography

Posted: January 2nd, 2011

Every now and then we see new images of M42... It's such an amazing - and difficult to image - nebula!

And more often than not, I've noticed that the famous dynamic range problem is solved by pasting and blending with a (painted) mask the short exposure that contains some detail in the trapezium area, with the longer exposure that reveals everything around it but a burned and saturated trapezium.

And I wonder... Why are they still doing it like that?

A while ago, when there weren't many (any?) HDR combination tools available, the trick of masking the short exposures of the trapezium and blending it with the longer exposure was slick, and it worked well.

Today however, there are plenty of HDR tools out there. Photoshop itself comes with one built in, there are plenty of plug-ins and standalone apps, and some of our favorite astroimage processing apps like PixInsight and others also come with them. And they do a pretty good job at resolving this well-known dynamic range problem..

Daylight photographers use HDR tools all the time. Even casual point-and-shoot photographers do - sometimes horribly but sometimes in really amazing ways. Why are they using them but we're not? I see astrophotography as one of the most complicated areas in photography, yet many astrophotographers still resort to the "old blending trick" just because "it works", instead of using these "new" techniques that now are available and that, I may add, are extremely easy to use.

Are we running so much behind?? Have we fallen asleep? In our field we really don't have many chances of applying these techniques because we seldom run in such strong dynamic range issue. Really we have M42 and just a few more objects that are ideal targets for this. But for that very reason we should be eager to use these tools in these very few chances we have, and show "them" (daylight photographers) that we know how to deal with extreme high dynamic range problems "properly".

Well, of course, this is not about showing anything to anyone. That's just a wake-up expression if you will.

In a way I think this is more than just a debate between using an HDR tool or resorting to copy/paste/blend. We shouldn't think everything has already been invented when it comes to astroimage processing and that the only way this hobby can advance is by means of the optics and especially CCD technology. Image processing can evolve as well, but if we're so slow in adopting something as simple as using an HDR tool (as I said earlier, it really doesn't take a lot of skills to use it, the tool does mot of the job), then it won't.

I won't tell experienced imagers that they need to change their ways. They have set the ground, and pioneered in very amazing ways. Whether they choose to adopt using "new" tools or different ways to process their images is a personal decision that must be respected. But at the very least, younger imagers (whether in age or simply new to the hobby) should look around, see the tools they now have at their disposal, and also try to be creative, just like the previous imagers were, back not too long ago with the tools they then had. Let's not just cook the recipes that have been written, cooked and eaten a hundred times. Let's write our own! Then someday, others too will pick up from where we left and continue pushing this discipline even further. That's exciting! Anything else is probably just dull and repetitive, and... what is fun about that?



Adam Nemec (Contact, Page), January 4th, 2011, 10:10
As someone who specializes in daytime photography (with a bent on HDR for the past 8 years) I wholeheartedly agree.

However, I started doing astrophotography just about a year ago and attempted several HDR images of M42 specifically using the techniques and software (Photomatix, Photoshop) I rely on for daytime shots, but with mediocre to poor results. This may have been because I was so new to this field and had not really figured out the equipment (specifically fine-tuning my mount and guiding). But even recently as my skill and understanding has progressed significantly I have still been disappointed with the blending of something like various exposures of M31 to draw out the core. Perhaps Photomatix is not ideal. Perhaps I am not correctly calculating my exposure lengths to truly draw out the HDR.

How do you calculate your exposure lengths for things like the M42 trapezium area?

RBA (Contact, Page), January 7th, 2011, 5:25
Hi Adam.
One should be able to do a nice HDR composition just by taking one set of exposures as short as 10~20 seconds merged with longer exposures of over 5 minutes. Of course you can do more elaborated compositions with an intermediate set, say with exposures within 1 minute, but with just two sets it should still work.

I wouldn't recommend using software like Photomatix, and instead use more specialized software for astroimaging that also has HDR composition capabilities, such as PixInsight.

zoila miranda (Contact, Page), January 7th, 2011, 5:55
Hola Rogelio, se terminů La FADD?

Adam Nemec (Contact, Page), January 7th, 2011, 8:32
Thanks Rogelio.

I have been contemplating the move to PixInsight for several months now. I did the free trial and liked it, though the learning curve seems a bit steep. But then again, what part of this hobby doesn't have a steep learning curve.

Photoshop is great, but the specialized nature of PixInsight makes it intriguing. I found that for daytime photography using Photomatix, which is a specialized software specifically for HDR compositions, produced images which were dramatically better than using the HDR features supplied within PS. Which makes me think that PixInsight will be much the same.

So it looks like I know what my next software purchase will be. Keep up the amazing and inspirational work.

rob (Contact, Page), March 19th, 2011, 11:31
i've successfully used the free software called enfuse to do HDR compositions of M42. now of course i use pixinsight. adam, if you are still reading this you might give enfuse a try. in my case, instead of feeding it linear images i did about 10 stretches of the same data and it did a very good job of picking the un-overexposed pixels from each image.

david (Contact, Page), October 14th, 2019, 6:15
In a way, I think this is more than just a conversation between using an HDR tool and copying / pasting / blending.When it comes to astroimage processing, we shouldn't assume that everything has already been invented and that the only way this hobby can advance is through optics and particularly CCD technology.

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