where there’s smoke there’s forum fire
I was just wondering if you were to take a 3 to 4 hr star exposure, to show how the stars are moving, could that fry my camera CMOS sensor.
Anyway a friend of mine have this great picture: a winter scene, with a cabin and app a 4 hr exposure. Was shot with film
Pete
Dont think it will mess up your sensor.. unless you are shooting the sun !! However, There is software that automatically stitches consecutive expotures of 30 mins for star trails .. cant remember the name of the software .. just google "star trail photography software" I am sure it will come up.. (too sleepy to do it now..) Good night all..
As heartyfisher said. Don't think it will destroy the sensor. Certain camera sensors can end up with hot pixels; the D90 is one.
As Gentoo said, noise of all three major varieties is a real issue @ such long exposures. Make sure you have enough battery to do that long exposure AND the equally long NR shot. (Though the merits of doing a NR shot IF temperatures are not ~comparable is debatable.)
Yeah, I have heard that shooting at the sun can kill your sensor, but I'm not exactly sure what sort of brightness you'd need.
But according to the other members, no. So I take their word for it. If my D40 dies doing a 4 hour exposure, each of you owe me a D40!
Been thinking.
I've never done a "mega" long exposure (> 30 minutes) with digital. Has anyone here? The more I think about it the more it seems the reciprocity failure* of film is to your advantage when shooting star trails.
* http://en.wikipedia.org/wiki/Reciprocity_%28photography%29#Reciprocity_failure
Nope, I haven't done anything over a couple seconds. The lowest I go is usually 1/8th handheld. Any lower than that, say 2-4 second exposures, and I just lay the camera on the table and set the camera to fire 3 seconds after I press the shutter. I don't have a tripod, so that's the best I can do.
Interesting article there Soap. I don't really get reciprocity failure after reading the article. Is it because there's so few photons flying around that your photo is going to be way under exposed? That's what I got from it.
The reason matters less than the results - film has a non-linear response to light at the long and short ends, and digital sensors have a linear response to light.
The reason I bring it up is because it is just this non-linearity of film which not only makes it harder to blow out highlights and underexpose shadows, but what should make star trails easier to get with pretty results on film.
Because film gets, in essence, less sensitive to light the longer you expose it you can leave the shutter open for long periods of time (long enough to get mondo trails) and not need to worry so much about the foreground blowing out from even the smallest sources of ambient light. Digital, on the other hand, should be more susceptible to small ambient lights overpowering the sky.
I say "should" because the proof is in the tasting, and I haven't baked such a pudding.
;)
(which is why I asked if someone else had.)
Okay, I see what you mean.
No idea why, but for some odd reason film is more alluring to me.
Maybe it's because I grew up without being interested in photography when it involved film, and now that photography has gone digital (for the most part), I feel like I got left behind and want to pick up film again.
Just back from a great day at work with a free gift from a Software Company (I will actually make a new post on that one)
Anyway I think some time ago I read a post about someone that fried the sensor on a 40D Canon from a 4 hour star exposure, I know this could newer happen on a Nikon. Anyway I think I will try this on my Film Camera and maybe just stick to normal pictures with my DSLR's
I might use my D300 to figure out what film speed(ISO) to use and camera settings. I know the lights on the cabin was only on for a very short time and then turned of for the remaining exposure, Actually I will ask if I can share the picture with you sometime. BTW Hi is all Nikon
Pete
My old D50 automatically cuts off at 30 mins. Mind you, there were some nasty hot spots. It you want to do long exposures then stick with film.
The longest exposure I've done was 50 seconds with my D90. I posted that photo a while back
I found this 11 Hour star exposure, I want to try something like this this winter. I wonder how you determine exposure time. I would do it outside town with a view that would slowly be exposed along with the stars. I think my old Nikon should be OK with being left outside in the cold all night long.
Pete
You don't want to shoot a "long" exposure of the sun because the rays are reflected straight at your sensor and the heat will melt it. Like a magnifying glass on an ant.
I played around with long exposures earlier this summer. >2hr exposures were not a problem, save for the battery running out. Here are my notes:
camera tripod mounted with eyepiece cover & remote trigger
full manual, bulb setting, autofocus off (to save battery, but getting sharp focus in dark was tricky)
long exposure NR on or off (I was trying to catch meteor trails and wasn't sure if they'd be cleaned out; otoh, fireflies added trails of their own to some shots)
exposure depends on the lens you're using. Here's an example with the 35 mm prime, 24 min @ f 5.6, iso100
The biggest thing I found was trying to keep light down. If you want good long trails, you need time. Any light from the moon, passing cars, nearby cities, etc. washes out your pic and makes your background an unsatisfying brown. Better hope the clouds don't roll in. Planes and satellites can give you odd streaks too (not sure if NR would help there).
edit- gah! cruddy jpg artifact not visible in original. star colors muted too.
I know some cameras like the D70,D80 suffer from big time amp glow with long exposures.
Ok found the software.. yes I had a good nights sleep :-) http://www.startrails.de/html/software.html
see we do get wiser from looking at forums ... well maybe :-)
Oh and ants don't melt they go pop !
The long exposure noise reduction shot will completely remove amp noise assuming consistent temperatures (different temperatures during the two shots will produce a black image with different levels of hot pixelation and amp noise (but still likely better than nothing))- but will do nothing to remove airplanes / satellites.
Sorry I was referring to amp glow
I did some looking to understand soap's comments and NikoDoby's comments above. For anyone else who doesn't know how long exposure NR works: after a long exposure, the camera takes an equally long second shot with the shutter closed. The second shot should show only internal camera noise, i.e., amp glow and hot pixels that are positionally constant. These are subtracted from the first shot.
Given that, it is clear that brief external "noise", like a firefly or a plane, will not be scrubbed out of the image.
If by amp glow you're referring to the non-photon-activated light well charge building as a result of heat from behind the sensor, (commonly seen as glow or exposure around the edge of the frame) the long-exposure noise reduction shot will kill that quite effectively - so long as ambient temps are close.
Dark-frame shots should effectively kill all systematic noise, as that is what you're creating an inverse of - much like balanced lines on professional microphones/speakers.
what he said ;-)
Fanny they call it digital noise when it is mostly analog in origin, but it will accumulate during low light long exposures, and rising sensitivity (effectively rising the power of amps around the sensor and by that also lowering SNR) will only make it worse.
As for damaging sensor is exposed to light about equally as during normal shooting so unless you are shooting for couple of hours straight to the sun there should not be any damage.
But some people are saying that sensor could actually damage itself during long exposures due to overheating, I personally have never found any proof of this claim.
Long exposure noise reduction will significantly lower the dark current noise but it will not remove all the noise and smear so soap is probably right, film was better for long exposures and mostly due to its non liner characteristics that are usually called reciprocity law failure effect.
This is amp glow and to my knowledge there is no fix with Noise Reduction software. Certain cameras exhibit the problem more than others. These are not my photos but this is what I've experienced with some of my own cameras.
Yea - that's amp noise. Heat noise as I described above.
A dark frame of equal length to the exposure subtracted from the desired photo should cancel that out below the existing noise floor.
That's what Nikon calls their long-exposure noise reduction, not their high-iso noise reduction.
Systematic noise can be eliminated through balancing techniques - be it in audio with balanced connections (think XLR ended cables) or in ethernet with twisted pair (so that the two conductors get equal and opposite amounts of noise from common sources) or in geodetic leveling where you run in a loop forwards and backwards to cancel out any consistent problem.
Random noise can't be eliminated that way, and that's where noise reduction software comes in. For random noise (well first you try to minimize it) you try to model it, and then use said model to identify it and mitigate it.
EDIT: Or think of it this way:
You treat systematic errors by repeating and keeping what is different. (shutter closed exposure of same length means the only thing in common is amp noise and hot pixels)
You treat random errors by repeating and keeping what is the same. This is impractical in photography, but not impossible - that's why you end up modeling noise and sieving it as I mentioned above.
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