In-Camera NR...

Candid Arts · March 2, 2009

When is it good to have the in-camera noise reduction on or off? Also, same question with long exposure NR on or off?

I guess I'm asking, if you're not using high ISO, is it negatively affecting the photo to have NR on? Same goes with the latter, if you're not doing long exposures, is it negatively affecting the photo to have long exposure NR on?

I hope this made sense... Thanks everyone in advance!

scole · March 2, 2009

Candid Arts wrote:

When is it good to have the in-camera noise reduction on or off? Also, same question with long exposure NR on or off?

I guess I'm asking, if you're not using high ISO, is it negatively affecting the photo to have NR on? Same goes with the latter, if you're not doing long exposures, is it negatively affecting the photo to have long exposure NR on?

I hope this made sense... Thanks everyone in advance!

The only negative I'll mention is that it will double your exposure time so a 5 minute exposure becomes a 10 minute exposure since the camera will expose a second image for the same duration in order to know what in the exposure is noise. Of course, that will drain your batteries a bit faster as well.

So I guess the negative can be that you might not have that much time to experiment and get everything right (exposure, composition, etc). You'll probably glad you did use it when you get it right, though!

ziggy53 · March 2, 2009

Candid Arts wrote:

When is it good to have the in-camera noise reduction on or off? Also, same question with long exposure NR on or off?

I guess I'm asking, if you're not using high ISO, is it negatively affecting the photo to have NR on? Same goes with the latter, if you're not doing long exposures, is it negatively affecting the photo to have long exposure NR on?

I hope this made sense... Thanks everyone in advance!

It is my understanding that using the high-ISO NR will tie up part of the shot buffer, reducing both the number of frames you can record as well as reducing the ultimate frame rate. Long-exposure NR definitely creates a "dark frame" as required, but I think it kicks in after a 1/2 second or longer exposure and does not impact shorter exposures at all.

In-camera NR does not seem to degrade the fine detail as much as some noise reduction software, but some folks claim nearly equal results using the "best" NR software.

My own strategy is to use both NR settings as it makes sense and to turn them off when it makes sense to do that. I like options.

Pindy · March 3, 2009

Haven't tested the 5DmkII, but on the Nikon long-exposure NR turned on means the burst goes from 19 RAW to only a handful, maybe 7 or 8. I don't notice a change with "high ISO" NR.

Candid Arts · March 3, 2009

ziggy53 wrote:

It is my understanding that using the high-ISO NR will tie up part of the shot buffer, reducing both the number of frames you can record as well as reducing the ultimate frame rate.

Pindy wrote:

Haven't tested the 5DmkII, but on the Nikon long-exposure NR turned on means the burst goes from 19 RAW to only a handful, maybe 7 or 8. I don't notice a change with "high ISO" NR.

So does the high-ISO NR or Long-Exposure NR change the burst rate? I kinda got contradicting thoughts here...

But from what I've gotten so far, turn high-ISO NR off when not using high ISO. and turn long-exposure NR off when not doing long exposures. Only use them when you need them?

ziggy53 · March 3, 2009

Candid Arts wrote:

So does the high-ISO NR or Long-Exposure NR change the burst rate? I kinda got contradicting thoughts here...

But from what I've gotten so far, turn high-ISO NR off when not using high ISO. and turn long-exposure NR off when not doing long exposures. Only use them when you need them?

Long-exposure NR is going to be slow when you use it but it should not affect the shot buffer when it is not using the Long-Exposure NR, as in short exposures.

Yes, I recommend only using the high-ISO NR when you need it. On the 50D that would start at ISO 800 or so for most applications.

Candid Arts · March 3, 2009

ziggy53 wrote:

Long-exposure NR is going to be slow when you use it but it should not affect the shot buffer when it is not using the Long-Exposure NR, as in short exposures.

So the High-ISO NR turned on affects the shot buffer then?

Ziggy53 wrote:

Yes, I recommend only using the high-ISO NR when you need it. On the 50D that would start at ISO 800 or so for most applications.

Which I tend to not go above anyways...unless ABSOLUTELY necessary, or for a specific effect.

ziggy53 · March 3, 2009

Candid Arts wrote:

So the High-ISO NR turned on affects the shot buffer then? ...

That is my understanding and I kind of "feel" the effects when I use it on the 40D, but I haven't really timed or counted to verify how much of an imapct it has on the shot buffer.

Candid Arts wrote:

...
Which I tend to not go above anyways...unless ABSOLUTELY necessary, or for a specific effect.

I should think that ISO 1600 would be usable for quite a bit and ISO 3200 fine when you really need it, but get the exposure correct by the histogram.

I grew up with film and today's high-ISO digital SLRs are just wonderful by comparison.

CWSkopec · March 3, 2009

Here's a shot I took with long exposure noise reduction on:

I took it the night I discovered that I had long-exposure noise reduction, so I'm not expert. I took quite a few shots that night, some with it on and some with it off. I don't see any degraded image quality with it on, just far less noise. This was a 7 minute exposure and there was hardly a speck of noise when I looked at the raw file. Other shots, starting at just 45 seconds or so, show noise in the form of "hot pixels." From all I've gathered, the long expo NR just eliminates these. How exactly it does that, I haven't found an answer. What I do know is that the camera took an "exposure" right after this one and the exact same length and sought out the "hot pixels" then extracted those from this shot, probably by blending the surrounding pixels. Zooming in, I can't find where it did that.

If you're planning some long exposures at night, it's a good idea to use them, but I would recommend figuring out your exposure exactly, then turning it on. I made the mistake of turning it on and then trying a five minute exposure... which meant that I had to wait around for 5 minutes while it took the "dark frame" then I tried a 6 minute exposure... waited for 6 minutes... tried 6.5 minutes... waited 6.5 more minutes... etc... Good thing it was peaceful!

I'm certainly no expert, but those are the facts as far as I know them, however that might not mean much in the so called "Real World." Hope they help!

PS - the second exposure isn't an actual exposure in that it doesn't show up on you CF card, it's just a tool that the camera uses to clean up your actual image.

Candid Arts · March 3, 2009

ziggy53 wrote:

That is my understanding and I kind of "feel" the effects when I use it on the 40D, but I haven't really timed or counted to verify how much of an imapct it has on the shot buffer.

I should think that ISO 1600 would be usable for quite a bit and ISO 3200 fine when you really need it, but get the exposure correct by the histogram.

I grew up with film and today's high-ISO digital SLRs are just wonderful by comparison.

I haven't been impressed at all with ISO above 800 on my 50D. I must be not properly exposing my photos? I've been shooting a lot of film lately for my beg. B&W photography at school. Highest I've shot thus far is ISO 400 (Illford) and haven't had any noise (grainy) issues with my 8x10 prints so far. I'd have to look at some of my ISO 400 shots with my 50D and have them printed to see the difference. But on my monitor, I can most certainly see noise even at ISO 400. Reasons like this are why I've brought up this question. I thought because I have both in-camera NR turned on all the time, it's doing something to the photos when I'm not "in need" of those NR settings (kind of like when a lens has IS but is mounted to a tripod...).

Thanks for the info Ziggy.

Candid Arts · March 3, 2009

CWSkopec wrote:

Here's a shot I took with long exposure noise reduction on:

I took it the night I discovered that I had long-exposure noise reduction, so I'm not expert. I took quite a few shots that night, some with it on and some with it off. I don't see any degraded image quality with it on, just far less noise. This was a 7 minute exposure and there was hardly a speck of noise when I looked at the raw file. Other shots, starting at just 45 seconds or so, show noise in the form of "hot pixels." From all I've gathered, the long expo NR just eliminates these. How exactly it does that, I haven't found an answer. What I do know is that the camera took an "exposure" right after this one and the exact same length and sought out the "hot pixels" then extracted those from this shot, probably by blending the surrounding pixels. Zooming in, I can't find where it did that.

If you're planning some long exposures at night, it's a good idea to use them, but I would recommend figuring out your exposure exactly, then turning it on. I made the mistake of turning it on and then trying a five minute exposure... which meant that I had to wait around for 5 minutes while it took the "dark frame" then I tried a 6 minute exposure... waited for 6 minutes... tried 6.5 minutes... waited 6.5 more minutes... etc... Good thing it was peaceful!

I'm certainly no expert, but those are the facts as far as I know them, however that might not mean much in the so called "Real World." Hope they help!

PS - the second exposure isn't an actual exposure in that it doesn't show up on you CF card, it's just a tool that the camera uses to clean up your actual image.

First of all, beautiful photo. Aside from your 7 minute exposure, what were your other settings?

Now I've seen this term "dark frame" in this thread earlier, but haven't heard of it. And it's making me question if I have long-exposure NR turned on or not because I've taken a few long exposure shots, and haven't noticed the camera take twice as long as the exposure is...

So what you're saying is, with long exposure (for future reference, I'm just going to say LE NR) NR turn off, expose the picture properly. Turn LE NR on, and take the photo. It will take the photo at the required time length, then expose the sensor again for the same time length to identify the "hot pixels" and clean them up? I definitely haven't noticed my camera do this before. I'll have to look into this a bit.

Thanks for all the help guys!

CWSkopec · March 3, 2009

Candid Arts wrote:

First of all, beautiful photo. Aside from your 7 minute exposure, what were your other settings?

Now I've seen this term "dark frame" in this thread earlier, but haven't heard of it. And it's making me question if I have long-exposure NR turned on or not because I've taken a few long exposure shots, and haven't noticed the camera take twice as long as the exposure is...

So what you're saying is, with long exposure (for future reference, I'm just going to say LE NR) NR turn off, expose the picture properly. Turn LE NR on, and take the photo. It will take the photo at the required time length, then expose the sensor again for the same time length to identify the "hot pixels" and clean them up? I definitely haven't noticed my camera do this before. I'll have to look into this a bit.

Thanks for all the help guys!

Let me start out with a Thank you!

Other notable camera settings were ISO 100 @ f4.5

I took this just a couple days after a full moon so there was still plenty of ambient light. The stair case was also lit up by a far off street light.

From what I've gathered, one of the main problems with digital cameras that film cameras don't experience during long exposures is that the elements inside heat up just because they're "on." That build up of heat over a long exposure causes some of the pixels in the sensor to think they're collecting data that's not really there. In some of the exposures I took before I turned LE NR on, there are very random red, green or blue pixels which is just a result of that pixel overheating and acting up.

So the theory behind LE NR is that, within a short time period (ie. successive shots) the same pixels will light up. So when LE NR is on, the camera creates this "dark frame" which is just an exposure at the same length of the previous shot with the shutter closed. If there wasn't an issue with hot pixels, it would be a pure black image. But those hot pixels will show up as a pure red, pure green or pure blue so the camera can find & identify them easily and subtract them from the previous frame. Then it just discards the "dark frame" since there's no more use for it.

On my XTi, when LE NR is on, right after the exposure is taken, I get a "BUSY" not on the LCD and the CF indicator is lit up. If you haven't seen either of those, it's probably not on, but I really don't know how your 50D handles it. The 50D probably handles hot pixels better without it on anyway. If you wanted to test it, you could try taking a 1 minute shot at night and checking to see if you've got those random hot pixels. Then find LE NR and turn it on, take another 1 minute exposure and compare.

I sure hope that most of that makes sense... I've had a couple cocktails this evening, so feel free to ask for clarification... I'll answer tomorrow, when I'm smarter!!

Candid Arts · March 3, 2009

Thanks for all the info, and yes it made sense.

I went and looked at my camera this morning and it was set to LE NR: Auto. Which "For 1 sec. or longer exposures, noise reduction is performed automatically if noise typical of long exposures is detected. This [Auto] setting is effective in most cases. The ON setting says, "Noise reductions is performed for all exposures of 1 sec. or longer. The [ON] setting may be effective for noise that cannot be detected or reduces with the [AUTO] setting.

I tested a 15sec exposure with LE NR off. It took the photo, and that was that. Then I turned LE NR on (not auto). 20" exposure now (I have my camera on Av). Took the picture, then once it was done, the number of photos left number was flashing, no Busy though, and it did that for 20". I took another photo at 15" (i don't know why it's changing, camera is on a tripod in my room facing my closet), but this time once I heard the shutter close and the numbers were flashing again, I tried to push the shutter to take another picture, then the Busy came up, and wouldn't let me take a photo 'till it was done.

I did the last test because everytime I've taken LE shots thus far, to the best of my knowledge, I've been able to focus and re-shoot right away. This after some 2 minute up to 25 minute exposures. So I wanted to see if by having it on auto, it's actually turning on. But when I had it in the ON position it wouldn't let me take a photo when it was processing. I would imagine that, when in the AUTO position, if it get's enabled by a LE shot, I wouldn't be able to focus and re-shoot correct? So...either I've just, by chance, been waiting long enough after every LE shot I've done to not notice it, or it's never enabled... Hmmm... I think I'll just be using OFF or ON from now on when needed.

Now for my High-ISO NR settings, there are Standard, Low, Strong and Disable. Factory setting is Standard, which is where I have it. Like I said though, I tend to not shoot above 800, 400 really, and only when I REALLY need to, or for that specific effect. Here is what it says in my manual for the High-ISO NR:

"Reduces the noise generated in the image. Although noise reduction is applied at all ISO speeds, it is particurally effective at high ISO speeds. At low ISO speeds, the noise in the shadow ares is further reduced. Change the setting to suite the noise level."

Is it best to have that set at Strong to try and eleminate as much noise, in-camera, as possible? Or will that have a negative effect on non-high ISO speeds?

Candid Arts · March 3, 2009

FWIW, all the previous test shots mentioned were at ISO 100.

I went back and tried again, but using AUTO at 15". As soon as the shutter closed, I could take another picture, there was no processing time. So I thought, maybe it's because I have it at ISO 100, and there's not enough noise for it to be needing to do the extra LE NR. So I turned the ISO to 400, no NR. ISO 800...no NR. ISO 1600!...no NR. All were on the AUTO setting, all shutter speeds of 1"3' or longer... SO, I have no idea how to get the AUTO setting to actually turn on and apply the LE NR...

ziggy53 · March 3, 2009

Candid Arts wrote:

...

Now for my High-ISO NR settings, there are Standard, Low, Strong and Disable. Factory setting is Standard, which is where I have it. Like I said though, I tend to not shoot above 800, 400 really, and only when I REALLY need to, or for that specific effect. Here is what it says in my manual for the High-ISO NR:

"Reduces the noise generated in the image. Although noise reduction is applied at all ISO speeds, it is particurally effective at high ISO speeds. At low ISO speeds, the noise in the shadow ares is further reduced. Change the setting to suite the noise level."

Is it best to have that set at Strong to try and eleminate as much noise, in-camera, as possible? Or will that have a negative effect on non-high ISO speeds?

It's best to look at the Canon explanation of how high-ISO NR works so you can see whay you might use the different settings, or even when to use post processing NR software:

http://www.usa.canon.com/dlc/controller?act=GetArticleAct&articleID=1407

Candid Arts · March 3, 2009

ziggy53 wrote:

It's best to look at the Canon explanation of how high-ISO NR works so you can see whay you might use the different settings, or even when to use post processing NR software:

http://www.usa.canon.com/dlc/controller?act=GetArticleAct&articleID=1407

Excellent link. Thank you.

So it seems, because I'm using LR and/or CS3, that the HIGH-ISO NR is useless to turn on in-camera because I shoot RAW and when using a third party editing software program, such as ACR, it will probably ignore the camera settings... If using Canon's DPP, then putting the high-ISO NR to to Standard if you need the higher fps burst rate, or strong if you don't would be ideal. But for users who are using third party software, might as well just disable it as it seems...

I tried to find an article such as the one you linked but for LE NR...but couldn't seem to locate it. I would be interested in reading Canon's review on the in-camera LE NR as well.

ziggy53 · March 3, 2009

Candid Arts wrote:

...

I tried to find an article such as the one you linked but for LE NR...but couldn't seem to locate it. I would be interested in reading Canon's review on the in-camera LE NR as well.

As far as I know, "all" camera manufacturers use the same method for long-exposure NR and it is based on the technique of "dark frame subtraction":

http://en.wikipedia.org/wiki/Dark_frame_subtraction
http://www.takegreatpictures.com/HOME/Columns/Digital_Photography/Details/Dark_Frame_Subtraction_using_Adobe_Photoshopby_Chris_Limone.fci
http://www.anandtech.com/digitalcameras/showdoc.aspx?i=2351&p=2

SteveF · March 3, 2009

I've meant to do this for some time, but have never gotten around to it. Maybe I will soon now that it is on my mind, unless someone here beats me to it.

Set up a dark studio scene that will take a, for example, 5 minute exposure.

Shoot it with and without the in-camera noise reduction.

Then apply a NR program (whichever is your favorite - I currently use Noiseware) to the file without NR done in camera.

Then compare the in camera NR to the computer based NR.

If the in-camera is better then it is worth the time. But if it is not significantly better than the time delay of the in-camera NR seems not worth it.

Candid Arts · March 3, 2009

SteveF wrote:

I've meant to do this for some time, but have never gotten around to it. Maybe I will soon now that it is on my mind, unless someone here beats me to it.

Set up a dark studio scene that will take a, for example, 5 minute exposure.

Shoot it with and without the in-camera noise reduction.

Then apply a NR program (whichever is your favorite - I currently use Noiseware) to the file without NR done in camera.

Then compare the in camera NR to the computer based NR.

If the in-camera is better then it is worth the time. But if it is not significantly better than the time delay of the in-camera NR seems not worth it.

You'll also want to take a picture with in camera NR on and then use your NR software to see it's results. Might find out that the best combination is to use both? I don't k ow, never used NR software, just LR2, CS3 and DPP.

In-Camera NR...

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