RAW and long exposure processing

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Grumpy_Git

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351
Name
Nick
Edit My Images
Yes
Hey

A quick question from the uninitiated, I'm off to Africa soon and want to try some Star Trailson the long cold nights (I've four batteries so have some spare power.)

I'm planning on shooting all my photos in RAW and was wondering if anyone has advice if I should have my long exposure noise reduction off or on, basically will my D90 even care about this setting if I'm shooting in RAW?

Cheers for any advice.

Nick.
 
Just remember that if you take a 10 minute exposure, you'll then have to wait another 10 minutes while the noise reduction frame is taken before you can take the next photograph.

You might be better off taking several shorter exposures which can be stacked together later, and which is another way of improving the signal to noise ratio.
 
as far as i know for the long exposure NR (as oppose to the iso nr which only effects the jpg) it does RAW-RAWdarkframe=savedRAWfile.
I take my own dark frames (lenscap on, apeture small to help further) and subtract it afterwards (this way you dont have to wait after every frame (including the ones you then delete)).

I often do 30seconds stacks as its more convenient, you can then add them in camera to check the exposure, again this operation is performed on the RAW files and gives you an outputted RAW (on the D80)
 
Thats good info B3R, will have to find out if I can stack in my D90 too, I've got a 16Gb and an 8Gb card for the trip so even though I will have decent amounts of storage, I cant take 60 x 30sec exposures as it would eat into the elephant photos lol.

Taking just 1 dark frame for a 3 or 4 photo set would be a good time saver (obviously a new dark frame each night!)

Any guides stacking frames in camera?

Cheers

Nick.
 
To avoid people breaking into my house, I'll not say when till I'm back.

As for where, I will be spending most of my time in Botswana although we shall visit Zambia, Zimbabwe and J'burg where my wife has family.

Nick.
 
Grumpy_Git said:
To avoid people breaking into my house, I'll not say when till I'm back.

As for where, I will be spending most of my time in Botswana although we shall visit Zambia, Zimbabwe and J'burg where my wife has family.

Nick.
Click to expand...

Pity you are not coming further south.

If you do, get in touch:thumbs:
 
Grumpy_Git said:
Any guides stacking frames in camera?.
Click to expand...

retouch menu (the pencil)-Image Overlay

-I tried kenrockwell as his starter guides are quite good but all he had to say on this one is "This one's silly, but you can drop two images on top of each other to create a final composite.

it only works with source images in NEF." -little does he know ;)

but if you follow the menu as per the above then its pretty self explanatory from there. the output is a separate raw file.
 
Switch off noise reduction whether you're shooting 30 sec or 30 min exposures. It really isn't worth the time for the results it offers. Without it you either get twice as long shooting or get home in half the time :thumbs:

As for image overlay, it's a very handy feature and it does need raw files as its basis but if the camera quality is set to raw + jpg you'll get the overlaid image in both formats even if you only shot the originals in raw. But one thing you won't find in the menu is that there's a gain feature built in so overlaying 2x 30sec exposures will give ambient light equivalent to a 1min exposure, and that'd be no good for star trails.
 
Another reason for taking multiple shorter exposures - it's about not having all your eggs in one basket.

As the night cools down, you might have to worry about condensation on the lens. You won't necessarily see it form, but it can ruin your photos. If you're taking lots of "short" photos, then at least the ones you take before the onset of dew will be usable. (This happened to me once. Details here.)
 
The series of short subs shot in jpg, without noise reduction works great. startrails doesn't accept raw... I've tried both a single exposure and a string of short exposures... the short exposures work much better and far more easily.

The other thing short exposures is great for... if you get a plane or satellite passing through the frame (and you don't want it there)... you can just paint over the track in black on the offending subs and when you combine them, the object will disappear. Although if you get a satellite flare I think it really adds to it...

This was an attempt to capture a meteor shower, and I threw all the images into startrails, because I could :D...

Startrails2.jpg
 
just reading a couple of things here...
when my camera says 'busy' for 15 mins after doing a 15 minute exposure, it's because of the noise reduction?
how long does it take to save if the noise reduction is off? (I know I can test it myself, but thought I'd ask anyway :D )
 
Gavin, that's correct. With ICNR turned off, you can go straight onto the next shot, Shooting in RAW you can fire off 6 frames before the buffer fills up and you have to wait, but that's when you're talking at normal shutter speeds.
 
RacingSnake said:
just reading a couple of things here...
how long does it take to save if the noise reduction is off? (I know I can test it myself, but thought I'd ask anyway :D )
Click to expand...

It takes no time cos there is no noise reduction wizardry going on.
 
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