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What if I can't afford PhotoShop?


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This is a quick, rough example from a DSLR. With an 8-bit image, you have only 256 levels of shade per colour channel. Normally the DSO is quite dark when I load the image and I have to "stretch" the image to make the dark areas of the DSO brighter. The DSO might only be covering about 10% of the available shades originally, about 25 shades in an 8-bit image, so it just isn't going to have that much detail in it compared to 16-bit.

That said, you can still do some great pictures using an 8-bit image editor if e.g. you use free software to do an initial stretch of the image in 16-bits while converting it to 8-bits to load into the 8-bit editor. I think I did this when I tried GIMP a few years ago but I can't remember if GIMP had an importer that let you stretch or whether I used some other free software to do that.

Another problem with 8-bits is that as you keep making adjustments you can lose details if you adjust contrast multiple times etc.

For me personally 16-bits is essential as I make a lot of adjustments. I really liked some of the things about GIMP and can't wait to try out a 16-bit version!

What's the real life difference of 16bit vs 8bit? Has anyone got a straight comparison of an 8 bit image vs a 16 bit image? I'm guessing it could be quite subjective?

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Yes, I'm not entirely sure which side of the argument you're on there, Olly :)

James

The technically minded will insist on 16 bit and clailm that it's a world ahead. All my stuff until a couple of years ago, and likewise Tom O'Donoghue's, was all done in 8 bit. 16 bit is obviously better but a quick reality check might be in order!

Olly

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The technically minded will insist on 16 bit and claim that it's a world ahead. All my stuff until a couple of years ago, and likewise Tom O'Donoghue's, was all done in 8 bit. 16 bit is obviously better but a quick reality check might be in order!

Olly

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8 bit it may be, but it's a belter of an image Olly! :icon_salut:

Thanks. The point is that I have since shot new M42s and processed them in 16 bit and the difference is distinctly underwhelming. This was at a shorter FL, a faster F ratio, had more exposure (20 hours) and had an 8 hour H alpha layer.

http://ollypenrice.smugmug.com/Other/Best-of-Les-Granges/i-R4v6bFN/0/X3/M42-WIDE-2FLs-X3.jpg

Do use 16 bit if you can but let's not get all 'Cloudy Nights' about it and take an elitist view of one small corner of the imaging equation. A copy of CS3, which will work in WIndows 7, is an almighty investment when it comes to the total cost of your setup.

Olly

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8 bit processing need not lose any visual data if, like Olly, or Tom O'Donoghue, you know what you are doing. Processing order is far more critical, because certain simple processing tools (such as non-linear contrast stretches) can lead to information loss. Because 16 bit tends to lose less information, you can be far more cavalier about processing order. Errors do not accumulate half as much (actually they are 1/256 times smaller). However, if you want to do anything in the Fourier or wavelet domain, intermediate steps had better be in double-precision floating point, or you will soon be bathing in artefacts. This can actually be done in certain tools which only allow import and export of 8-bit data.

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I still use Photoshop7 which is I believe was Olly's workhorse. It will process levels and curves in 16bit but to use virtually everything else must change to 8bit. Thus most of the detail can be extracted in 16 bit.

Rather than upgrade photoshop I have bought AstroArt5 which I am just getting to grips with. This has loads of bells and whistles and I can still add a few touches in ps7.

I have also been playing with another imaging program that my grandson has picked up for £10...Serif Photplusx4. This will process 'raw' images and is similar in use to PS with levels,curves and loads more. Here is a link........ http://www.serif.com/photoplus/phpx4.aspx?MC=SERPPCPHP1&gclid=COqknYX3_7ECFUNkfAodnAgAMg

It is not the latest version, hence the price.

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I've used IRIS for a long time http://www.astrosurf...s/iris/iris.htm

It's free

It's 16 bit

It's excellent at pre-processing and less good at post processing and a touch tough to drive but rewarding and powerful, works best from the command line although can be menu driven.

I'm looking to upgrade currently and am dithering between PS via the 'cheap' route or PixInsight.... I'm vearing strongly towards the latter.

Derek

I think the majority of options in PS are available in PI but it's a case of finding them - PS has more examples out in the interwebs.

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I think the majority of options in PS are available in PI but it's a case of finding them - PS has more examples out in the interwebs.

Thanks.. I'm vering towards PI as it seems capable of doing some things that PS can only do by obscure routes.. basically it's built for the job and I'm not looking at photoshop for daylight work.

of course the best solution would be to have both :grin:

Derek

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I still use Photoshop7 which is I believe was Olly's workhorse. It will process levels and curves in 16bit but to use virtually everything else must change to 8bit. Thus most of the detail can be extracted in 16 bit.

Rather than upgrade photoshop I have bought AstroArt5 which I am just getting to grips with. This has loads of bells and whistles and I can still add a few touches in ps7.

I have also been playing with another imaging program that my grandson has picked up for £10...Serif Photplusx4. This will process 'raw' images and is similar in use to PS with levels,curves and loads more. Here is a link........ http://www.serif.com...CFUNkfAodnAgAMg

It is not the latest version, hence the price.

You're right and I was wrong to say my M42 was all in 8 bit. Brain fade!! Of course Ps7 did many things in 16 bit, I had forgotten. ANyway a chepo copy of Ps7 would be a good bet if ever one came up.

Sorry about my error there.

Olly

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You're right and I was wrong to say my M42 was all in 8 bit. Brain fade!! Of course Ps7 did many things in 16 bit, I had forgotten. ANyway a chepo copy of Ps7 would be a good bet if ever one came up.

Sorry about my error there.

Olly

thanks.. I can stop thinking "how on earth did he manage that!!!" (plus or mnus the odd four letter word)

Derek

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It's an 8-letter word Olly takes exception to (starts with C). ;)

quikly googles for 8 letter words beginning with C

8 letter words starting with c: 2659 words

random selection:

curtains?

custards?

curdling?

crystals?

crumbling?

coxswain?

cowpoxes?

I don't think it's any of those.. if it is, the mind boggles!

Derek

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