Long Exposure degrades quality?

jamesino

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Suppose I set up a camera on a tripod. I take two shots: one with a 1 second exposure and another with a 1/500 second exposure. Suppose all in-camera controls (aperture, ISO...) are constant, the only difference is that the ambient lighting is darker for the 1 second exposure, will the longer exposure be less sharp than my shorter exposure?

Does opening the shutter for long period of time introduce more noise into the picture?
 

benpsut

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Opening the shutter does induce more noise. Keeping it open for one second? Doubt there will be noise. Now if this was a night shot, yes probably, although you'll be using more than 1 second if your ISO was the lowest possible. SO, the longer the shutter is open there's going to be noise, no matter if you have low low ISO. NOW, supposing we're talking about a daytime/ lit shot, 1 second exposure is going to give you a BRIGHTER exposure, not darker. 1/500 will give you a darker shot. I don't have the time to explain it to you if you don't understand, it's really common sense if you've been doing this for a little bit, no offense. The only quality you will lose for the 1 second exposure is camera shake if hand held, motion blur i the subject is moving or from trees or grass or whatever if the wind is blowing. If you want to induce motion, set your shutter speed to 1 second or even up to 3, i wouldnt go past 3. THEN set your aperture til the light meter says it's correct lighting for the exposure. That why the shot won't be too dark or over exposed but you'll get that feel of motion in the shot. Good luck!
 

macdsean

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As mentioned above, long exposures at night can cause a lot of noise. Many cameras have the ability to compensate for this (my Nikon D50 has a menu setting).
 

manaheim

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I think OP was asking about sharpness, though... not noise.

james... are you talking about blurriness of the pictures? Or random dots of color?

If the former, are you using a tripod on your longer exposures, or are you taking the pictures holding the camera in your hand? Are you using a remote shutter release cable (or wireless remote)?
 
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jamesino

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I was actually referring to both. It appears that my long exposure shots are not as sharp as my shorter shots. I'm mounting the camera on a tripod and shooting with a mirror lock up followed by a 2 or 3 second countdown on a Rebel XTi.
 

manaheim

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I was actually referring to both. It appears that my long exposure shots are not as sharp as my shorter shots. I'm mounting the camera on a tripod and shooting with a mirror lock up followed by a 2 or 3 second countdown on a Rebel XTi.

Ok...

On blur... how stable is your tripod? Have you tried a longer countdown? With just 2-3 seconds, you may still be experiencing the results of your pressing the button by hand. I highly recommend getting a remote shutter release cable. They're relatively inexpensive and worth every penny. (figure $26-40... don't go cheaper... they break) You may also simply need a sturdier tripod. The typical sub-$100 model isn't always as sturdy as you would hope, though for a 1s exposure in normal conditions you would hope you would get away with it.

On noise... long exposures do introduce noise. It's a matter of the physics on how the sensor works, which can be shorthanded as saying "It heats up, causing voltage spikes and other oddities which wind up being represented as color inconsistencies in the capture."

That being said, a 1 second exposure shouldn't introduce any noticable amount of noise.

Can you post some examples for both short and longer shutter times so we can see?
 

chris

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Using a half decent tripod you should not have any problems with blur due to camera shake. However you still have subject movement to contend with and if there is anything that can move, such as foliage, it may well produce some blur even at times when wind speed is low.
 

Garbz

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Many things have already been said here and they are right, but don't let that scare you.
A 10 second photo at ISO100 has less noise in it than a 1/1000th photo at ISO400.
Dead pixels caused by thermal issues with long exposures die consistently so they are easily taken care of with long exposure NR or in photoshop with the clone tool afterwards.

http://farm1.static.flickr.com/204/483765404_1fbe2d624e_b.jpg
An example 3 minute shot at ISO200 I think. The blur in the foreground was caused by me firing the flash multiple times.
 

Computer_Generated

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Gotta say I have a huge issue with sharpness. I think it's my crap tripod and I'm cheap so I don't have a shutter release. Somethings happening from the time I push the button and the exposure is done after the timer goes off. I think my tripod is moving the camera a hair when I push or when the shutter opens... it's pissin' me off though.
 

benpsut

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From the time the exposure starts, if there is any shake present, even the smallest that you can't see physically, it WILL show up. Just think, the camera is picking anything up from the very beginning of the exposure to the very end and everything in between. So a hair of shake from the milisecond you let go of that button, most likely will be picked up in the long exposure in the beginning of it. It doesn't matter if it's a one second exposure or a 30 second exposure, if the camera shakes for les than a fraction of a second in the first half second of that 30 second exposure but is steady through out the 29 in a half more seconds, it still will show up. Not as a big blur but that "lack of sharpness" you are describing. I picked up my cable release off of amazon for 20 bucks and it's still intact and works beautifully, invest in one.
 

Rachelsne

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I use self timer on 10 seconds, as I cant afford shutter release at the moment. 10 seconds is long enough for the camera shake to stop after you press the button
 

TamiyaGuy

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I'd agree with getting a remote for your camera. I mean, what can you buy for £15 nowadays (sorry, I don't work in dollars)? A couple of beers? A pizza? Or you could get something that will allow you to take flawless night time photographs. Although to be honest, I manage to do OK with a 2-second self timer and a tripod.

Another thing that I think has not yet been mentioned is that it may be the scenery that is moving. For instance, trees may be swaying slightly in the wind in the background. Because they're swaying so little, the movement might not have the characteristics of "normal" camera shake, but might look as though the lens is not sharp.

Another thing is that the noise reduction processing used on cameras with 1s or longer exposures might make the image a little less sharp (although it shouldn't make any real noticable difference).

There ya go. Best of luck getting those shots!
 

Computer_Generated

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Another thing is that the noise reduction processing used on cameras with 1s or longer exposures might make the image a little less sharp (although it shouldn't make any real noticable difference).

Well that's a really good point, I always forget about in camera processing. Just out of curiosity I can understand on the JPG images, would this sharpness thing happen with the RAW images too? I've just started to do the JPG+RAW... so I haven't been able to check the differences.
 

TamiyaGuy

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I don't think it should. RAW files are, essentially, the data from your camera's sensor. No processing done at all. Because of this, RAW files usually need some post-processing done to make them look their best, but when it is done (well :p), the results are better than a JPG.

Another option, if you want to keep shooting JPGs, is to turn off any kind of noise reduction in your camera. I've read somewhere that you can individually turn off both high-ISO noise reduction and/or slow shutter speed noise reduction in a Nikon D200, although I'm not sure about other cameras. Try turning off all noise reduction your camera has, then try again. Although like I said, it shouldn't make a massive difference. I've done 30-second long exposures which are nice and sharp.

Actually, if you have any sharpness issues with long-exposure photos, check the aperture you were using. Very small (or large) apertures can degrade lens performance, but yet again, the difference isn't mind-blowing.
 

Bifurcator

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Right, it won't kill the detail in RAW (because RAW is not processed at all) but I wanted to add that in-camera NR for very noisy images will just destroy image detail and leave the photo looking muddy and dull (as in not crisp & sharp!). It depends on the amount of noise it has to remove.
 

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