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If we just left our images unprocessed they would be very unimpressive with many targets not actually visible, especially with 16bit CCDs. So we change our image. Are there any boundaries to what is acceptable and what isn't, anything that we should declare when we post? I have read comments from people on other forums who seem to have quite strong views that we should.

There seem to be different levels of what is considered appropriate -

1)global changes such as histogram stretches, global sharpening and saturating.

2) targeted manipulations - contrast enhancement, selective colour balance and sharpening.

3) doctoring the image to remove defects - use of clone, healing brush and smudge tools

4) Adding data which isn't there - painting in a faint central star or colourising (e.g. artificially adding colour to white stars which just isn't there in the data)

5) Copying in data from an image that isn't yours :shock:

I make some very heavy duty changes to images especially when it comes to colour information. Also I enjoy blitzing halos with the smudge and other tools. I love the healing brush. Should this trickery be declared? I don't see much point in (4) but would tell people if I'd done it. Having said that, if a corner of an image has been cropped out I will happy use the clone tool to fill it with stars and black sky. As for (5)...

Interested to hear what others think

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I do 1, 2 and 3 to all my astro images, and often will adjust my normal daytime images in similar sorts of ways (obviously not so heavily in the histogram adjustments). It seems that even for photography, this is accepted practice. It's even accepted (except for sharpening) for images on the stock photography sites that some image manipulation is carried out, even if it's only cloning out dust spots. I personally would not do 4 or 5. I've never considered indicating what sort of processing is carried out, except in discussions around processing themselves, and again this seems to be the norm for daylight photography too.

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I don't have any problem with options 1,2 and 3, perhaps with the exception of 'saturating' in option 1.

IMO, the whole idea of image processing, is make as clearly visible as possible, all the data/detail that is contained in the original image, as captured by the camera. After all, if I 'posted' a RAW image from my H9C, it would be mono, and with very little detail visible. Its all in there, but needs processing to make it visible.

Removing CCD defects, such as 'hot pixels', is 'par for the course'. Correcting star shapes, e.g. coma, is maybe cheating a bit?.


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I think there's a number of ways to approach this:

If you're producing an image of something and represent it in such a way that it is realistic, then global manipulations in are ok - such as levels, curves etc. As I think this is manipulating data that is already there in a relatively clean way.

Where actions are taken to work on just a small part of a given image then this gets a little tricky as the image then becomes an interpretation of what the producer thinks it should look like - a bit like "an artist's impression of". There's absolutely nothing wrong with this in my mind, it just should never be claimed to be the realistic, "as is" view of an object. It should be stated that "parts of the image have been modified to......." so the viewer knows what they are looking at.

Now if smaller localised actions are taken to remove imperfections in an image caused by dust, internal refelctions, star trails or similar then I think this should be stated clearly. Again, nothing wrong with doing this, it just needs to be acknowledged as data is being removed from the image.

For me, my own humble opinion, I get a lot more enjoyment out of looking at images that have had the minimal about of manipulation - I think I focus more on what an image represents than how it looks (never been really into art).


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I regularly do 1,2 & 3.

Where coma and star trailing has to be fixed, although I often say that I've done it, I don't see the need to as stars are round, so all you're doing is sorting out an image train defect, much the same as fixing hot pixels etc.

4, absolutely not, and 5 is a hanging offence!



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My goal is to be able to create images that I like to look at, they don't need to be scientifically accurate, but they must only be based on the data that I have gathered, otherwise instead of spending hours collecting data you may as well just make it up. Getting the very best out of the data is part of the enjoyment to me.

I have heard people describe what I do as "glorified photography" :) but hey, I do this for my enjoyment and therefore I can set the rules by which "I play the game" :)

Cheers Jon

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As well as the "normal" stuff there DBE or gradient exterminator, Noels astro action... etc...

And with Registar the ability to combine data form various sources... like we have for the M42 Group project...

Where do we stop...

Process for "art" rather "than" science.... The clone tool can easily inadvertently add or remove stars ....


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Surely if you are only enhancing the information in the data you have captured, there can be no ethical conflict. Adding data that isn't there cannot be acceptable, and unless I am completely naive, no one with a conscience would do so.

I'm sure the Images down from Hubble, Spitzer, and the like, are manipulated too, and they go out on a commercial basis in the form of posters etc.

Pre Digital work by David Malin surely would have received enormous attention to turn them into the masterpieces they looked.

Let your conscience be your guide usually works.

Whenever I get around to processing an Image of my own, I will use everything I have to improve it, but only the data I collected, nothing added.


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an interesting and age old question. Some of the most famous photographs made by Frank Meadow Sutcliffe had clouds added to them by adding in layers of tissue paper when he was printing his wet collodion negatives. Extensive retouching has always been done in conventional photograpic prints, and the negs when they were 10 x 8. Edward Weston, when he was part of the original Group f64 said that any print that was not a contact print on glossy paper shoud be regarded as impure. Not everyone was as straight as him.

I have removed cars, yellow lines, street furniture and people as well as dust and scratches from my prints although I was limited to dust and scratches before we went digital.

Why should astro prints be any different? So long as people are honest I would think anything goes. I touch up my prints on the basis of doing as little as possible but when you use a blooming camera that can be a lot of work.

I do certainly draw the line at stealing someone else's data though. A case for dunking their sensitive bits into liquid nitrogen and then hitting said bits with a hammer.


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If we had Hubble type equipment, would we need to carry out excessive processing? I suppose the same goes for those with a 50mm compared to a 300mm lightbucket.

Since I haven't taken any real images yet, although I have all the kit, I do enjoy working on many of the images posted on SGL. I must say that I do like the M42 composite.


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I find 1, 2,3 completely acceptable

adding things that arent there or adding data that is not yours without stating is a hanging offence (sorry rob, stole your line)

mind you, I have seen a narrowband crab with dtat from spitzer and chandra used. He did state that he used the telescopes.

if you dont plagarize its fine to add otherwise unavailable data


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If I look at an image taken by an imager I'd assume that some (or all) of 1) to 3) had been done to the image, but I'd also like to be able to assume that 4) definatly hadn't been done at all unless he imager specifically mentions it (inc. stamping non-existent in stars in corners :) :) ). If its not a true representation of the actual object and the surrounding area captured then I think that any 'modifications' should be mentioned, if only for the reason that there is the slight possibility that people may use the image as a reference for other "work".

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I think 1,2, & 3 are pretty much a given, even with my fairly basic processing skills I do pretty much all of them to varying degrees. 4 is a bit of a grey area for me. I wouldn't do it, but as long as the creator of the image said what he's done, than it's his perogative but I would like to see the original to make a comparison. Number 5? Like SteveL, no unless it's a group project.


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Very interesting responses, most people feel 1-3 are ok but not 4 and 5. I don't think anything is "cheating" because there are no rules but there are images which might be misleading which I don't think is right. Personally I think 5 is fine so long as it is acknowledged and you have permission. As is combining a low res wide field with a high res image of the target area taken with a larger scope.

I am guillty of using (4) so it's confession time :oops: ...and I didn't mention it :oops: :oops: I genuinely meant to but forgot. It was one of my little processing contributions to this weeks POW


compared with the original


Now I reckon that's a definite (4) which puts me firmly in the wicked category :)

Or how about this for a questionable (3). Here is Whippy's honest Jellyfish


And here is my process. Look at the change in the colour of that big star - that was using data that was there, giving some of it a massive shove and blocking other bits out. So it's a number 3 but would be seen by some as the spawn of satan


Now I love that splodge of contrasting colour, it is using existing data and might even be a truer reflection of what's up there but it feels a bit naughty :)

So I'll try to remember to own up to 4, will always do the decent thing with 5 and might sometimes come clean with the dirtier 3s

Off now for 50 Hail Mary's :sad11:

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Go easy on the self-flagellation Martin, after all you were only trying to be helpful!

Given the ready consensus here it seems to me the greater issue is that those unfamiliar with imaging automatically assume that everything is faked once the word 'Photoshop' is mentioned...


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Martin, put that cat o' nine tails away... What you've done to the jellyfish is fine IMO because you haven't taken data from another source and incorporated it into that image. How you manipulate that data is down to you and if you think it looks good, then great. I think for most people as long it's what was there in the first place and you're not adding 'extras' to the image, then you're pretty much free to do what you want :) .

How would false colour narrowband fit into the scheme of things? That's got far more room for 'artistic license' than Mono or straight colour hasn't it?


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i agree tony....

but the data was acquired with filters, again no extras added. The choice of colour map may be a lie...and usually is. Ha aint green.

But narrowband is still and accurate representation of whats out there.

from physics the Hbeta line is 2.92x weaker than Ha. What if someone took their ha image, and divided by 2.92 and called it Hbeta...is that fine?

physics says yes...what do you say?

i say its OK because its true.....an actual Hbeta image would be almost identical

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crikey, I'm going to buck the trend, I do 1 & 2, 3 is mostly ok I guess if you feel you have to and as long as you declare it, not so sure about the clone tool though, 4 tsk tsk, as for 5 I am all up for it as long as its declared. Personally I use you lot as a yardstick, a beautiful astronomy picture will always be appreciated, but certain aspects of the post processing not being declared may give a false impression to someone as to what their kit alone should realistically produce.

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