DSLR Long Exposure Processing Question

[Gerrit Gulden]

I have a Point and Shoot camera and have found that with Long exposures my processing time equals or doubles the original exposure. Such as a 64 second exposure photo processing time is around 1-2 minutes. My question is related to DSLR camera's and how long it takes for the processing to complete. If you use the Bulb setting and take a 10 Minute exposure how long does it take to process. Is there a difference between 5,10,15,30,60 second exposures and then Extremely long exposures such as several hour exposures if indeed the battery allows this.

I am closing in on my DSLR purchase and really felt I should ask incase One model differs from the other, etc.

Thanks...

 

[Jim Saueressig]

As far as I know all use the same time for noise reduction as they do for the actual exposure.

10 minute exposure has 10 minute processing.

 

[James Langford]

I can only speak from my Canon perspective. On my 10D, there is no noise reduction option, and you really don't need it at ISO 100 for exposures under a few minutes. Anything over that, and you could shoot a dark frame yourself to subtract out later in processing. On my 30D, there is a noise reduction option that takes just as long as the exposure you shoot, same as your point and shoot I imagine. The nice thing is that you can turn off the noise reduction. I never use it, as I hate the delay it creates, and noise is pretty easy to clean up in processing.

 

[Cris Schroeder]

My experience is the same as James. My XTi has a menu option to turn off the long exposure noise reduction. I leave it off. When active, the noise reduction takes the same time as the exposure.

 

[Mike Hollingshead]

Think about this too, you're going to be upgrading to a DSLR that should have a larger sensor than what you've been using and be much better in the noise department.

I've had 2 canon rebels now and a Sony F707. I don't know which ones have even had noise removal. I've never once used in camera noise removal in the last 6 years. It's pretty simple to do it after the fact, to the level you want, with an ap like Neat Image. You can make a layer with a filtered image, then place it on your original and adjust the opacity till it looks decent. I usually even do a mask over things like the foreground, where the noise was more detail than anything. No sense in killing detail for the sake of removing noise in the sky.

The noise difference from my first Rebel 300d and the Rebel XT 350d was huge. It was far far less, and it was a nicer form of noise. And even that not so great 300d rebel was way way better than the earlier F707 was(and hell that camera was $1000 at the time...the F707). If you are upgrading to DSLR you'll just see much better noise anyway, and especially so if your camera is older at all.

I understand the Rebel XSi has a new different format of noise removal that does well and doesn't take double exposure time to get it.

One thing to always remember with noise, don't under expose. An under exposed 100 ISO image will probably be more noisy than a well exposed 200 ISO image once the 100 ISO one is lightened. I'd even go as far as to say that with 100 ISO under exposed to 400 ISO properly exposed.

 

[Gerrit Gulden]

So the length of processing is mainly a Noise Reduction process and if your camera allows it, you can turn the Noise reduction off and have lower processing times? I always thought or assumed that with a DSLR and for the price there would be a stronger processor. Its like a Pc with 256mb memory (point and shoot camera) and then a 4gb memory (DSLR).

If you do decide to turn of the Noise Reduction and are shooting lightning will the result be a great image or would it need work? I imagine if you leave it on the image will be fine, youll just have a lengthy processing time.

 

[Dustin Wilcox]

Noise Reduction?? Is there some program that does such a thing? (No wonder my pics always suck) Some links as to where and what to buy would be much appreciated!!

 

[James Langford]

I use Noise Ninja, which has both a stand alone program, and a very nice Photoshop plugin. You can also download custom Noise Profiles for your individual camera. I don't have a link right now, but Google is your friend.

 

[Mike Hollingshead]

So the length of processing is mainly a Noise Reduction process and if your camera allows it, you can turn the Noise reduction off and have lower processing times? I always thought or assumed that with a DSLR and for the price there would be a stronger processor. Its like a Pc with 256mb memory (point and shoot camera) and then a 4gb memory (DSLR).

If you do decide to turn of the Noise Reduction and are shooting lightning will the result be a great image or would it need work? I imagine if you leave it on the image will be fine, youll just have a lengthy processing time.

Like has been commented on in other recent threads, yes, having noise reduction on extends the time.

There is almost zero need for noise removal with lightning images, either in cam or after the fact. If you leave it on you'll miss lightning...that simple. If that is cool, then have at it. I just know I fear that split second it takes me to unclick and reclick the cable release as it is. Some situations I'll ISO up when the lightning isn't terribly bright(lots of incloud stuff) and I want to get the storm lit up. Those are the only ones I'll need to later remove noise. And generally, for those scenes, noise removal isn't terribly kind to the shot/storm anyway.

It's really simple....download a noise removal ap and try it. I'm sure they come with free trial periods. Neat Image and Noise Ninja are the two that come to my mind.

 

[Darren Addy]

I think there are multiple issues the impact what the original questioner is asking about. Yes, the noise reduction is normally the biggest issue for the delay before writing to the card. The term "processing" though is a bit general. If you are talking about the amount of time before you can take another picture, you are discussing cycle times. Ignoring how full the buffer is, the cycle time is going to be affected by the in-camera processing PLUS the write time to the card. Some cameras will show significant improvement with a higher performance (faster transfer time) Compact Flash or SDHC card. The SanDisk Extreme III (SDHC) and Extreme IV (CF) are fast cards, for instance. When you get a real DSLR, there will also be issues such as whether you are shooting JPEGs, RAW or a combination (RAW +JPEG). The bigger the file(s) the longer it will take to write to the card (obviously).

But I agree that the noise reduction is the biggest single factor for the long cycle times on a long exposure.

To answer your question regarding battery life, a lot of DSLRs have the ability to accept an A/C adapter (if practical for where you are shooting). You can also get vertical grips for most DSLRs which allow you to double the amount of batteries you are shooting with. In any event, you will hopefully be using rechargables, so battery life isn't a huge concern anyway. My Pentax K200D takes AA size batteries rather than proprietaries, which is nice. You can get a couple of packs of Sanyo Eneloops and a charger and be good to go.

I highly recommend adding the Pentax K200D to the list of cameras you are considering. It's made to be good for people using their first DSLR, but also has the customization options that you can grow with for a long time. I'm pretty impressed with it so far, but have not yet tried long-exposures such as you are describing. Check out what people say about it in the Reader Reviews on Amazon. I think you'll like what you see when you compare features to the Rebels and entry-level Nikons.

 

[Mike Deep]

My understanding is in-camera noise reduction, at least with Canon, is intended to remove hot pixels. Like Mike said, it would kill you if you left it on when shooting lightning. The camera takes a second exposure of equal length with the shutter closed in order to perform noise subtraction. Hot pixels are absolutely trivial to remove in most image programs so I wouldn't worry about it.

Gerrit, if you're concerned about buffer timings on a DSLR, which is what it sounds like, you shouldn't be. Buffers in DSLRs are much larger and much faster than point and shoot cameras, and you can still compose and shoot even if images are still being written to the card, at least until the buffer is full - On most cameras that's at least nine RAW shots. For lightning it won't be a consideration at all.

 

[Mike Hollingshead]

Yeah I've often wondered about the noise removal name and how that would work. Doesn't that thing do more than remove hot pixels? I could see how it wouldn't and that would indeed make it seem even more useless if that's all it is improving(hot pixels).

And yeah, other than that added time if you want to use automatic noise reduction, there's no relevant write time issues for storm photography with any fairly new DSLR. Unless of course you are standing right by a tornado and a house is flying by you that you want to capture for photogrametry purposes, lol. I'd say with my first rebel, yeah, still a little slow between clicks on lightning(over a second if I remember correctly, and that could be too long if done at the wrong moment). With my second one, the XT, which is rather old itself, it's just about as fast as you can unclick and reclick the cable release.

 

[Dan Robinson]

The XSi can fire off at least 2-3 shots per second in continuous mode - no lag in between shutter close-open, which is a huge improvement over the point-and-shoots I've used in the past. In once instance, using manual 'reaction' triggering and continuous mode, I was able to get three successive images of a single lightning strike (return stroke and bead-out). That was in RAW+JPG mode (which I always use).

The buffer does run out quickly when you're doing rapid successive shots. 9 sounds about right in my experience, but it's rare when that happens.

 

[Darren Addy]

Hot pixels are white, and you'll often see them on long exposures. RGB noise is different colored pixels (reminds some of film grain) and will be seen in crappy light conditions at high ISOs (camera/sensor/etc. variable). If you are doing a long exposure AND doing it at high ISO, you will probably see both hot pixels and RGB noise in your images.

Noise reduction (generally speaking) is a way of "smoothing" the off-colored pixels by blending them by algorithm to a color that takes into account the surrounding pixels and makes an educated guess as to what it "should" be. This smoothing process will result in a loss of detail. It is a compromise, but not always a bad one. It may be best used in post-processing when you can apply it only to the areas of the image where noise is objectionable, rather than the image as a whole.

 

[Mike Deep]

Yeah I've often wondered about the noise removal name and how that would work. Doesn't that thing do more than remove hot pixels? I could see how it wouldn't and that would indeed make it seem even more useless if that's all it is improving(hot pixels).

I think as far as Canon is concerned, that's all it is. Hot pixels are a type of noise, I suppose.
From dpreview's XT review:

With the introduction (or return of depending on how you look at it) of custom functions the 350D allows you to enable or disable long exposure noise reduction. When enabled this noise reduction system works in the typical 'dark frame' manner, a second exposure immediately after the first but with the shutter closed, the noise pattern is used to remove 'hot pixels' from the image. In our tests up to the timed maximum of 30 seconds we couldn't find any evidence of hot pixels even with noise reduction switched off.