Long Exposures and Digital Cameras.

DRT-Maverick

As most of you know, taking long exposures of the sky or anything past 15-30 seconds results in quite a lot of 'noise' - Hot Pixels. I have yet to figure out a way to take LONG exposures, over 4 minutes, without completely deteriorizing the shot with hot pixels and making it not at all desirable. Any suggestions, or should I stick with Film for that, and have it professionally developed for scanning quality?

Andy

DRT-Maverick wrote:

As most of you know, taking long exposures of the sky or anything past 15-30 seconds results in quite a lot of 'noise' - Hot Pixels. I have yet to figure out a way to take LONG exposures, over 4 minutes, without completely deteriorizing the shot with hot pixels and making it not at all desirable. Any suggestions, or should I stick with Film for that, and have it professionally developed for scanning quality?

some of the best work, is done with multiple images, stacked.

take a look at luben's site for some stacking tutes. also, look at shay's tribute in light, and moonsteps shots in his fine art gallery. believe it or not, shay's moonsteps was done with a sony f717 ... not known for low noise! and i own a large print of "tribute in light" and man, is it buttery smooth, yet lots of details, too.

hope this helps.

DRT-Maverick

His tutorials section is currently under construction. What is stacking and how do I do it?

prity goldfish

i'd like to know as well, i've seen some people mention stacking, but i'm not sure what that means, is it where you take the same picture but stack it multiple times on top of itself? that is what it sounds like.

DRT-Maverick

Yeah, that's what it is, but how do you do it in photoshop?

DavidTO

I'm going to get really technical here, so hold on...

The 20D (and other cameras, I assume) have this long exposure thingie, that you set in a custom menu. It takes a second shot of the same exposure but without opening the shutter dealie, and somehow finds all the noise and hot pixel things and takes them out.

Or something like that...

prity goldfish

DavidTO wrote:

I'm going to get really technical here, so hold on...

The 20D (and other cameras, I assume) have this long exposure thingie, that you set in a custom menu. It takes a second shot of the same exposure but without opening the shutter dealie, and somehow finds all the noise and hot pixel things and takes them out.

Or something like that...

lol real technical!

DRT-Maverick

DavidTO wrote:

I'm going to get really technical here, so hold on...

The 20D (and other cameras, I assume) have this long exposure thingie, that you set in a custom menu. It takes a second shot of the same exposure but without opening the shutter dealie, and somehow finds all the noise and hot pixel things and takes them out.

Or something like that...

My pentax has that too, noise reduction. The problem with this is it kills photo time and battery life, by taking the same length exposure of a 'dark frame'. The darkframe won't cut down on any noise if the photo is a certain length though. It's quite useless over 4 minutes.

DavidTO

DRT-Maverick wrote:

As most of you know, taking long exposures of the sky or anything past 15-30 seconds results in quite a lot of 'noise' - Hot Pixels. I have yet to figure out a way to take LONG exposures, over 4 minutes, without completely deteriorizing the shot with hot pixels and making it not at all desirable. Any suggestions, or should I stick with Film for that, and have it professionally developed for scanning quality?

I don't have a whole lot of experience with long exposures, but one thing that you could try to reduce noise is to go into LAB mode and apply a gaussian blur to the a and b channels only. Try 3 pixels. If you select those two channels and then type ~ you will be effecting only those channels but seeing all three. This can greatly reduce or eliminate color noise.

Luminance noise is much trickier, of course, and will almost always result in lowered detail.

A search here on dgrin for "stacking" will yield a bunch of results.

XO-Studios

prity goldfish wrote:

lol real technical!

Actually fishy, your D70 has the same and it works quite well, not quite as well as stcking but still a very respectable result.

If there is still noise after that, use Neat Image (my fav) or Noise Ninja

XO,

prity goldfish

XO-Studios wrote:

Actually fishy, your D70 has the same and it works quite well, not quite as well as stcking but still a very respectable result.

If there is still noise after that, use Neat Image (my fav) or Noise Ninja

XO,

fishy? huh? you can use my name, it's kasey.

DRT-Maverick

XO-Studios wrote:

Actually fishy, your D70 has the same and it works quite well, not quite as well as stcking but still a very respectable result.

If there is still noise after that, use Neat Image (my fav) or Noise Ninja

XO,

XO, i've said it already multiple times. Real long exposures cause LOTS of noise. If you need an example of a 2 hour long exposure, here you go.
(I also did a darkframe shot to reduce noise).



Neatimage won't make a lick of difference, I assure you that.

I want to get shots like this, but clean, and the right color, like what you'd get with film.

dkoyanagi

DRT-Maverick wrote:

Yeah, that's what it is, but how do you do it in photoshop?

Hi Maverick
Here's some info on stacking. Hope this helps.

David_S85

Ed Murphy's PDF Stacking Guide:

http://users.zoominternet.net/~ed.murphy/stacking.pdf


The original thread he posted it in:
http://forums.dpreview.com/forums/read.asp?forum=1009&message=12832210

DRT-Maverick

Thanks guys, those are great sites!

Shay Stephens

My 2 bits
If you plan on star trail shots, stacking won't do a bit of good because the scene is changing. You need a static scene for stacking to work.

My suggestion is to do this kind of shot when it is very cold outside. Long exposures when the temperatures are high will result in terrible noise. Low temperatures (the lower the better) will give you much better results.

And get yourself in a darker location too, the moon and or light pollution isn't helping here at all.

Getting the color right is going to be a job for white balance adjustments or shooting in RAW and fine tuning the white balance in post. The farther you can get from city light pollution, the better, because it taints and tints the shots something fierce in long exposures.

DRT-Maverick

Shay Stephens wrote:

And get yourself in a darker location too, the moon and or light pollution isn't helping here at all.

There was a very small sliver of moon, oh, and I'm about oh, 5,000 miles above the last light pollution, as well as about 75miles away from any light pollution in all directions.

I don't know, it may be that the chip is CCD, I hear those are bad with hot pixels.

XO-Studios

DRT-Maverick wrote:

XO, i've said it already multiple times. Real long exposures cause LOTS of noise. If you need an example of a 2 hour long exposure, here you go.
(I also did a darkframe shot to reduce noise).

Neatimage won't make a lick of difference, I assure you that.

I want to get shots like this, but clean, and the right color, like what you'd get with film.

I am not debating that film is better, but by all means, goto this group http://groups.yahoo.com/group/Nikon-D70/ and do a search for astro photography. There are people out there using a D70 straight up getting way way better results than that.

Also a D70 tip, Nikon Capture (and PS CS as well with a work around) will allow you to make a noise reduction compensation shot ones, and have the software subtract that. I might have the terminology wrong, it might be called something else, but principle is the same.

Also, I gave it a go, and while not straight Neat Image, I think a lot can be done, see attached.

XO,

ps. before Gallileo, people many many times said the earth was flat.

Shay Stephens

Ok, that is good news. Shoot when there is no moon, and work on the white balance or shoot RAW and fine tune in post for best color results.

CCD or CMOS, they are both affected by temperature. Get the temps down low. The longer the exposure, the colder the camera needs to be.

DRT-Maverick wrote:

There was a very small sliver of moon, oh, and I'm about oh, 5,000 miles above the last light pollution, as well as about 75miles away from any light pollution in all directions.

I don't know, it may be that the chip is CCD, I hear those are bad with hot pixels.

DRT-Maverick

Neither was I debating on whether film was 'better' than digital, I never once said that, did I? I said that film doesn't have hot pixels or sensor noise, because well, obviously, it doesn't generate electrical heat.
Also, I don't shoot with Nikon (You can check my profile or even look at my signature), I shoot with Pentax. So that article really doesn't help me much.

Also, I don't want to lose that much detail, you lost half the stars in the sky. Granted the noise is gone, but there's no actual improvement on getting the clear star trails that I was looking for.

ps. before Gallileo, people many many times said the earth was flat. <-- not quite sure how I should take that comment.


P.S., on a side note, go out tonight, there's no moon from waht I see. Take a 2 hour exposure and please post your results.

XO-Studios wrote:

I am not debating that film is better, but by all means, goto this group http://groups.yahoo.com/group/Nikon-D70/ and do a search for astro photography. There are people out there using a D70 straight up getting way way better results than that.

Also a D70 tip, Nikon Capture (and PS CS as well with a work around) will allow you to make a noise reduction compensation shot ones, and have the software subtract that. I might have the terminology wrong, it might be called something else, but principle is the same.

Also, I gave it a go, and while not straight Neat Image, I think a lot can be done, see attached.

XO,

ps. before Gallileo, people many many times said the earth was flat.

DRT-Maverick

Shay Stephens wrote:

Ok, that is good news. Shoot when there is no moon, and work on the white balance or shoot RAW and fine tune in post for best color results.

CCD or CMOS, they are both affected by temperature. Get the temps down low. The longer the exposure, the colder the camera needs to be.

Yeah, I'll try that this winter in the sierras sometime Shay, maybe my results will be better. The temperatures will be a lot lower vs. the 50F summer nights (-10 and lower temperatures at night do occur). I'll have to post the results. If that can get me the desired effect, then it'll rock.

Thanks for the suggestion.

spockling

Caught this in July in Northern Idaho. It was probeably still 70+ degrees outside.


File: IMG_8175.CR2
File size: 7,042KB
Image Serial Number: 000-8175
Camera Model: Canon EOS 20D
Camera serial number: 0420102957
Firmware: Firmware 1.1.0
Owner: unknown
Date/Time: 2005:07:28 23:51:38
Shutter speed: 1878 sec
Aperture: 4
Exposure mode: Manual
Flash: Off
Metering mode: Evaluative
Drive mode: Single frame shooting
ISO: 100
Lens: 18 to 55mm
Focal length: 18mm
AF mode: Manual Focus
Image size: 2336 x 3504
Image quality: Raw
White balance: Auto
Color space: sRGB
Saturation: Normal
Sharpness: Normal
Contrast: Normal
Tone: Normal
Custom Functions:
CFn 1: SET button function when shooting: Change parameters
CFn 2: Long exposure noise reduction: On
CFn 5: AF-assist beam/Flash firing: Only ext. flash emits/Fires
CFn 8: ISO expansion: On
CFn 11: Menu button display position: Previous
CFn 13: AF point selection: Multi-controller direct
CFn 15: Shutter curtain sync: 2nd-curtain sync

DRT-Maverick

From what I've heard, CMOS sensors are far more capable of long exposures than CCD. *shrug*. It's what I've read at a few places.

Higgmeister

DRT-Maverick wrote:

My pentax has that too, noise reduction. The problem with this is it kills photo time and battery life, by taking the same length exposure of a 'dark frame'. The darkframe won't cut down on any noise if the photo is a certain length though. It's quite useless over 4 minutes.

Hey Tyler,
You are going to have lots of noise as that is the norm. I've seen some astro photography that doesn't look like it's worth anything till you post process it. That's when the image really begins to shine. There are techniques and applications out there that will get you what you want. Search for astrophotography and processing. There is more to the processing than just noise removal so be prepared to do some PP.

I found my info when I was researching the Canon 100mm f/2.8 macro and found out it's a wonderful astro lens.

Good Hunting,
Chris

DRT-Maverick

Thanks! I'll definitely give it a try, and I'll try shooting in RAW. Perhaps I'll get lucky and manage to figure out how to do it correctly. I've seen great shots of startrails with digital cameras, but never could figure out, and was pretty close to giving up on using digital for the trails.

gubbs

Luben also uses a tecnique where he blends a series of shorter exposures,
have a look at the zion star trail shot, here he blended 30 x 1 minute f2.8 exposures to get the star trails....

Luben, if you read this your new site's looking sweet

erich6

I'm resurrecting this thread because I tried a 1-hr exposure with noise reduction (NR) and without having seen this thread I came back with a very poor image. The NR does remove nonuniformities in the CMOS sensor but there are a lot of "hot" pixels in my 20D and these register the same value in both the image and the dark frame so I ended up with a bunch of outages.

I'll try "stacking" the next time. That should take care of preventing hot pixels from saturating.... My guess is that if you use this technique it's actually better to turn off NR because the pixels will just read as noisy and the stacking procedure will effectively clean them up. Otherwise you can end up with a similar effect as having outages and that would be harder to fix.

Can anyone comment on this?

Also, are there suitable interpolation algorithms out there for Photoshop that can fill-in these outages? I'm trying to see if I can recover my shot.

Erich

DJKennedy

erich6 wrote:

I'm resurrecting this thread because I tried a 1-hr exposure with noise reduction (NR) and without having seen this thread I came back with a very poor image. The NR does remove nonuniformities in the CMOS sensor but there are a lot of "hot" pixels in my 20D and these register the same value in both the image and the dark frame so I ended up with a bunch of outages.

I'll try "stacking" the next time. That should take care of preventing hot pixels from saturating.... My guess is that if you use this technique it's actually better to turn off NR because the pixels will just read as noisy and the stacking procedure will effectively clean them up. Otherwise you can end up with a similar effect as having outages and that would be harder to fix.

Can anyone comment on this?

Also, are there suitable interpolation algorithms out there for Photoshop that can fill-in these outages? I'm trying to see if I can recover my shot.

Erich

I would love to see the 1 hour photo. Best I've done with the 20D is 20 mins or so.

devbobo

DJKennedy wrote:

I would love to see the 1 hour photo. Best I've done with the 20D is 20 mins or so.

DJ,

Here's a shot of Luben's which is 90 minutes (9x 10 mins exposures)

Cheers,

David