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RAW vs JPEG


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I want to try to build up a workflow for prime focus DSLR astrophotography (using my Nikon D40 and C6-NGT) and after reading up on flats, bias, flat darks etc., etc. I have some very basic questions. I have tried to search for the answers on here and can't seem to find them but apologies if this has been covered before.

The first question is what format I should be using to take the pictures. I've read that for general photography there is little point in shooting in RAW since you then have to do in software what the camera electronics and firmware do more efficiently. Of course, I understand that often in astrophotography the usual rules don't apply so could I just ask if it is a no-brainer to shoot in RAW and a few words on why?

Thanks for any advice.

Edited by x6gas
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I just ask if it is a no-brainer to shoot in RAW and a few words on why?

It simplifies things enormously ... you can ignore white balance in particular & lots of other settings (including ISO if using suitable software) because all you're doing is recording what the sensor captures. Start converting & you're potentially losing information - big time if you use a lossy compression technique like jpeg - also the 8 bit image depth in jpeg is far less than the 12 or 14 bit sensors capture, and that extra low level info is very useful when stacking or enhancing images even if it isn't obvious in a straight print.

Set your camera to record raw & forget it.

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RAW is always better - to make a JPEG, the camera and firmware will average everything, according to the camera-maker's chosen programming. You will almost invariably do a better job yourself using Photoshop/Elements/Canon DPP, or the Nikon equivalent.

Think of RAW as a film negative - once you have got it, you can tinker to your heart's content to get the best possible image as a JPEG. The RAW image itself stays unchanged, so you can always return to it and create a different JPEG (more/less contrast, more/less exposure, different white balance, etc, etc.) from it. It is much harder to change the appearance of a JPEG - and many adjustments simply can't be made at all on a JPEG.

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I've read that for general photography there is little point in shooting in RAW since you then have to do in software what the camera electronics and firmware do more efficiently. Of course, I understand that often in astrophotography the usual rules don't apply so could I just ask if it is a no-brainer to shoot in RAW and a few words on why?

Thanks for any advice.

RAW all the way for any kind of photography! There's far, far more data captured in a RAW shot and a skilled (or even semi-skilled operator following an internet guide) can bring out far more with post-processing than any camera can. With jpg you're just chucking away vital data that you might well need in the future. There's not really any need to go for one or the other as most cameras have some kind of RAW+jpeg setting which is the best of both worlds if you just like the standard camera-produced images but want to archive the RAW shots for later.

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Thanks all for your kind and thoughtful replies. I can now happily snap away in RAW knowing that I am doing the right thing and hopefully (for astro stuff at least) never have to worry about it again.

For those that are interested, the website that set me on this path of uncertainty was this page about JPEG and RAW on Ken Rockwell's Nikon D40 guide.

Thanks again!

Edited by x6gas
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As others have said RAW gives many advantages such as being able to change the white balance setting after you've taken the shot. Try doing that when you've left your camera set on Tungsten while outside.

But... many professional photographers do still make use of JPEG, especially those with a dislike to Photoshop who prefer to get it right first time in-camera. To be honest unless you are doing lots of post processing you will struggle to notice the difference between a high quality JPEG and RAW.

Also, don't forget RAW takes up huge amounts of disk space and requires a meaty PC to process efficiently.

I'm not dissing RAW as it does of course have lots of advantages for some people but I certainly wouldn't disregard JPEG. I personally use both.

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Do Nikon cameras use RAW??

I thought I read somewhere that a Nikon Raw wasn't really a RAW at all....

But if theres a choice, raw is the way to go.

As I understand it, all RAW formats are different since it is just the 'raw' data read from the sensor, but yeah they have RAW output.

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I'll need to look for it but i'm sure i read that Nikon cameras apply an amount of processing before outputting a RAW format, in other words, take the shot, the camera makes some slight processing then you get a RAW, or the camera makes a larger process and you get a JPEG.

I think it was an article on the differences between Canon and Nikon for Astrophotography

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I'll need to look for it but i'm sure i read that Nikon cameras apply an amount of processing before outputting a RAW format, in other words, take the shot, the camera makes some slight processing then you get a RAW, or the camera makes a larger process and you get a JPEG.

I think it was an article on the differences between Canon and Nikon for Astrophotography

Ah.

Interesting.

I have no idea myself but it's certainly something else that I'll look in to (though I can't imagine why they would do this!)

Thanks!:)

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Thanks Rossco72 - seems you are right and that the Nikon cameras subtract a dark before saving in their RAW format. This doesn't seem like an awful thing to me (but then I don't know much about this) although it does mean that it effectively doubles the exposure time (though if it saves you taking darks, no foul?) but - unfortunately - it also then applies a median filter.

Don't know what this means in practice, other than you are 100% correct!

Thanks for the catch...

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I'll need to look for it but i'm sure i read that Nikon cameras apply an amount of processing before outputting a RAW format, in other words, take the shot, the camera makes some slight processing then you get a RAW, or the camera makes a larger process and you get a JPEG.

I think it was an article on the differences between Canon and Nikon for Astrophotography

Thanks again, Stuart, for highlighting this. I decided to get in touch with Nikon since my camera didn't seem to be spending the time taking a dark if I disabled the noise reduction. Here's the response:

"With regards to auto image processing done by the camera to reduce dark current noise and other digital imaging artifacts that can occur when capturing long exposures, as long as you disable the NR (noise reduction) option in the camera's shooting menu then the camera shouldn't be performing any such processing. You should notice that, with this option enabled, any exposure over a second in length will go through processing that lasts around the same amount of time as the exposure did (see page 73 of the D40 user manual). When this option is disabled however the camera shows the image on the screen almost as soon as the mirror flips back down - indicating that it's not performing any auto-post-processing."

I had asked about the application of a median filter as well as about the dark subtraction and they haven't mentioned that explicitly in the reply so I'll follow that point up...

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Either Canon or Nikon could really steal a march if they brought out a DSLR which was truely ideal for Astro.

No filter, no amp glow, low noise, high sensativity and a set of setting which helped during night time.

I'm sure it would be a hit and surely couldn't be too hard to adapt from their current lineups.

Cheers

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Sorry buy Kodak once marketed a DSLR using the same sensor found in top end cooled astro CCD cameras ... monochrome and lacking the IR cut filter built in ... apart from the lack of cooling, this would be ideal for astro use.

It was only on the market for a few months; nobody was prepared to pay a five digit sum (which is what it was worth) for a camera that wasn't even colour.

You get a lot of performance from cooling the chip. The dedicated astro CCD camera is the way to go, if you're really serious about DSO imaging.

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