How to reduce high ISO noise while shooting

BBear · 05-14-2008, 06:28 AM

Originally posted by Outlaw

So if I read correctly, what you have posted, if higher ISO is needed, then make sure to increase the exposure to compensate for noise and this will allow a faster shuuter?.

I thought i was understanding the whole topics... but the comment above threw me off: how can you increase exposure and have a faster shutter at the same time? (keeping aperture constant)

Wouldnt be the opposite? for the same aperture and same ISO, I had understood from the discussion that you'd basically have to stop down shutter to reduce noise.

anyone?

PentaxPoke · 05-14-2008, 07:44 AM

Originally posted by BBear

I thought i was understanding the whole topics... but the comment above threw me off: how can you increase exposure and have a faster shutter at the same time? (keeping aperture constant)

Wouldnt be the opposite? for the same aperture and same ISO, I had understood from the discussion that you'd basically have to stop down shutter to reduce noise.

anyone?

Bear,

I think Outlaw was asking a question to which I replied that there is a tradeoff. Yes for any given ISO, you either have to stop down shutter or aperture.

Let me propose one other idea: If one agrees with the argument in the Expose Right link, then the way we should expose our DSLRs is to the right at all ISO values. If that is the case, and that is the proper way to expose, then there really is no tradeoff at all between iso choices. There only is a tradeoff if you are comparing an exposed right image at a higher iso to a lesser exposed image at a lower iso.

See what I am saying? In other words; the argument of using a higher EV and then reducing sensitivity in the RAW converter compared to just a normal exposure at a lower iso is no longer valid, because the higher EV should be used at ALL iso values to reduce noise. Then with the advantage of RAW, and the fact that you have captured the most information possible with the sensor, you can adjust your picture down to any sensitivity to get the exact look you want.

jonboy · 05-16-2008, 04:57 AM

Originally posted by PentaxPoke

Who said blow highlights? Certainly not me! Did I blow the highlights in this example? No. Did you read my post above regarding highlights? Post #3. Seriously, it is basic forum etiquette to actually read a thread before commenting. There is a whole wide range between underexposure and blowing highlights.

1) Try not to be so cranky.
2) I read all your post (try not to be presumptuous, either)
3) With regard to your photos, because the conditions are indoors the exposure latitude is pretty narrow, so it'd be difficult to blow highlights in those lighting conditions. In the real world, however, over-exposing (which is what you're doing by increasing the exposure compensation) will almost always lead to blown highlights to some degree.
4) The only way to reduce noise is to use a low ISO, which will often mean a tripod in low light. Yes, software noise reduction (if applied skillfully) can make a big difference, but there's no magic bullet. When the sensor's gain is increased (which is what you're doing by increasing the ISO) then noise is a simple product of this process and is usually directly proportional.

RiceHigh · 05-16-2008, 05:38 AM

SONY ICX413AQ Exposure Latitude + Dynamics Linearity Test (Pentax *ist D + FA* 85/1.4 in RAW )

Originally posted by PentaxPoke

We have all heard about "exposing to the right" in order to increase signal to noise on the sensor. I thought I would run a demonstration of how this can be used to reduce high ISO noise without using noise reduction software, and without reducing detail.

Here is the setup:

k20d, ISO 6400
3 exposures: EV-1, EV0, EV+1
No NR of any type
Shot in RAW, converted to jpeg on "Natural" and "Highest Quality" (be careful of download size)

The EV-1 was "pushed" +1 to get to EV0. The EV+1 shot was "pulled" down to EV0. Compare all the shots. You will see that the noise in the EV+1 "pulled" is significantly lower than the other two. You could make the case to just set the camera to ISO 3200, but I am just trying to illustrate the improved signal to noise of exposing to the right using 1EV steps (because it is convenient)
Expose Right to reduce ISO noise test - a set on Flickr

WMBP · 05-16-2008, 08:12 AM

Originally posted by jonboy

And blow out your highlights? No thanks, that's not for me.

jonboy, take a look at the "Expose to the Right" article at Luminous Landscape. The suggestion is that you expose to the right as far as you can without blowing important highlights. The article explains why you should do this and it's pretty cut and dried. Boils down to this: The way digital sensors work, you capture at LOT more info at the bright (right) end of the histogram. If you're so scared of blowing any highlights at all, you end up getting photos with considerably less dynamic range. Note that I said, without blowing important highlights. There's nothing wrong with blowing unimportant highlights, and you have to do this all the time - that or lose shadow detail, and often you have no good choice but to do both.

The problem, I find, is that it's really hard to tell what's an important highlight and what's not just by looking at the camera's histogram or even using blinkies (letting the camera tell you what's getting blown). So if I'm shooting outdoors in the sun, and especially if the sky is in the shot anywhere, I almost never get a histogram that's weighted to the right, because if I do, I've usually blown important highlights and can't recover them. SO I find myself often having to expose for the highlights, and then bring the midtones and shadows up in post-processing. And that of course brings in noise. I'd like not to do it this way. I accept the rationale of the expose to the right idea. But in practice, what I really need isn't to push my exposures to the right - I need a camera with greater dynamic range!

Will

PentaxPoke · 05-16-2008, 08:59 AM

Will,

Your summary pretty much nails it. I think the place where expose to the right is very helpful, and a lot easier to do, is for indoor shots. I find that in those situations, it is easier to avoid clipping because the lighting range is not as wide. As you mention, I agree it may be harder outside. If one has the time to adjust after the shot, and shoot again it is certainly easier to get a proper right exposure.

jonboy · 05-17-2008, 07:17 AM

Originally posted by WMBP

There's nothing wrong with blowing unimportant highlights, and you have to do this all the time - that or lose shadow detail, and often you have no good choice but to do both.

I'm not convinced there are "unimportant" highlights. However, I think it should be recognized that the whole issue, to a large extent, is a subjective one. There is no such thing as perfect exposure; a certain amount of sacrifice has to be accepted in order to achieve the photographic objective at the time.

I think that working in RAW is a big factor, and a small but significant amount of detail can often be recovered with a little patience and experimentation.

Originally posted by WMBP

But in practice, what I really need isn't to push my exposures to the right - I need a camera with greater dynamic range!

Ah! Now isn't that just the truth. We're all chained to the limiting factors of currently available technology. Another five years will see enormous changes, and another ten will, I suggest, be very much a different world. So all things considered, these are rather exciting times.

Oh, and if I've come across as a little bit too strongly opinionated, I apologize.

05-14-2008, 07:44 AM	#17
PentaxPoke Veteran Member Join Date: Jan 2008 Location: Oklahoma Posts: 1,411 Original Poster	Originally posted by BBear I thought i was understanding the whole topics... but the comment above threw me off: how can you increase exposure and have a faster shutter at the same time? (keeping aperture constant) Wouldnt be the opposite? for the same aperture and same ISO, I had understood from the discussion that you'd basically have to stop down shutter to reduce noise. anyone? Bear, I think Outlaw was asking a question to which I replied that there is a tradeoff. Yes for any given ISO, you either have to stop down shutter or aperture. Let me propose one other idea: If one agrees with the argument in the Expose Right link, then the way we should expose our DSLRs is to the right at all ISO values. If that is the case, and that is the proper way to expose, then there really is no tradeoff at all between iso choices. There only is a tradeoff if you are comparing an exposed right image at a higher iso to a lesser exposed image at a lower iso. See what I am saying? In other words; the argument of using a higher EV and then reducing sensitivity in the RAW converter compared to just a normal exposure at a lower iso is no longer valid, because the higher EV should be used at ALL iso values to reduce noise. Then with the advantage of RAW, and the fact that you have captured the most information possible with the sensor, you can adjust your picture down to any sensitivity to get the exact look you want. Last edited by PentaxPoke; 05-14-2008 at 11:20 AM.

05-16-2008, 05:38 AM	#19
RiceHigh Veteran Member Join Date: Nov 2006 Location: Hong Kong Posts: 1,934	My Old Lengthy Experiment SONY ICX413AQ Exposure Latitude + Dynamics Linearity Test (Pentax ist D + FA 85/1.4 in RAW ) Originally posted by PentaxPoke We have all heard about "exposing to the right" in order to increase signal to noise on the sensor. I thought I would run a demonstration of how this can be used to reduce high ISO noise without using noise reduction software, and without reducing detail. Here is the setup: k20d, ISO 6400 3 exposures: EV-1, EV0, EV+1 No NR of any type Shot in RAW, converted to jpeg on "Natural" and "Highest Quality" (be careful of download size) The EV-1 was "pushed" +1 to get to EV0. The EV+1 shot was "pulled" down to EV0. Compare all the shots. You will see that the noise in the EV+1 "pulled" is significantly lower than the other two. You could make the case to just set the camera to ISO 3200, but I am just trying to illustrate the improved signal to noise of exposing to the right using 1EV steps (because it is convenient) Expose Right to reduce ISO noise test - a set on Flickr

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05-14-2008, 06:28 AM	#16
BBear Veteran Member Join Date: Mar 2008 Location: CT / NY Photos: Gallery Posts: 822	Originally posted by Outlaw So if I read correctly, what you have posted, if higher ISO is needed, then make sure to increase the exposure to compensate for noise and this will allow a faster shuuter?. I thought i was understanding the whole topics... but the comment above threw me off: how can you increase exposure and have a faster shutter at the same time? (keeping aperture constant) Wouldnt be the opposite? for the same aperture and same ISO, I had understood from the discussion that you'd basically have to stop down shutter to reduce noise. anyone?

05-16-2008, 04:57 AM	#18
jonboy New Member Join Date: Apr 2008 Location: Cambridge, UK Posts: 9	Originally posted by PentaxPoke Who said blow highlights? Certainly not me! Did I blow the highlights in this example? No. Did you read my post above regarding highlights? Post #3. Seriously, it is basic forum etiquette to actually read a thread before commenting. There is a whole wide range between underexposure and blowing highlights. 1) Try not to be so cranky. 2) I read all your post (try not to be presumptuous, either) 3) With regard to your photos, because the conditions are indoors the exposure latitude is pretty narrow, so it'd be difficult to blow highlights in those lighting conditions. In the real world, however, over-exposing (which is what you're doing by increasing the exposure compensation) will almost always lead to blown highlights to some degree. 4) The only way to reduce noise is to use a low ISO, which will often mean a tripod in low light. Yes, software noise reduction (if applied skillfully) can make a big difference, but there's no magic bullet. When the sensor's gain is increased (which is what you're doing by increasing the ISO) then noise is a simple product of this process and is usually directly proportional.

05-16-2008, 08:12 AM	#20
WMBP Veteran Member Join Date: Dec 2006 Location: Dallas, Texas Photos: Gallery Posts: 2,482	Originally posted by jonboy And blow out your highlights? No thanks, that's not for me. jonboy, take a look at the "Expose to the Right" article at Luminous Landscape. The suggestion is that you expose to the right as far as you can without blowing important highlights. The article explains why you should do this and it's pretty cut and dried. Boils down to this: The way digital sensors work, you capture at LOT more info at the bright (right) end of the histogram. If you're so scared of blowing any highlights at all, you end up getting photos with considerably less dynamic range. Note that I said, without blowing important* highlights.* There's nothing wrong with blowing unimportant highlights, and you have to do this all the time - that or lose shadow detail, and often you have no good choice but to do both. The problem, I find, is that it's really hard to tell what's an important highlight and what's not just by looking at the camera's histogram or even using blinkies (letting the camera tell you what's getting blown). So if I'm shooting outdoors in the sun, and especially if the sky is in the shot anywhere, I almost never get a histogram that's weighted to the right, because if I do, I've usually blown important highlights and can't recover them. SO I find myself often having to expose for the highlights, and then bring the midtones and shadows up in post-processing. And that of course brings in noise. I'd like not to do it this way. I accept the rationale of the expose to the right idea. But in practice, what I really need isn't to push my exposures to the right - I need a camera with greater dynamic range! Will

05-16-2008, 08:59 AM	#21
PentaxPoke Veteran Member Join Date: Jan 2008 Location: Oklahoma Posts: 1,411 Original Poster	Will, Your summary pretty much nails it. I think the place where expose to the right is very helpful, and a lot easier to do, is for indoor shots. I find that in those situations, it is easier to avoid clipping because the lighting range is not as wide. As you mention, I agree it may be harder outside. If one has the time to adjust after the shot, and shoot again it is certainly easier to get a proper right exposure.

05-17-2008, 07:17 AM	#22
jonboy New Member Join Date: Apr 2008 Location: Cambridge, UK Posts: 9	Originally posted by WMBP There's nothing wrong with blowing unimportant highlights, and you have to do this all the time - that or lose shadow detail, and often you have no good choice but to do both. I'm not convinced there are "unimportant" highlights. However, I think it should be recognized that the whole issue, to a large extent, is a subjective one. There is no such thing as perfect exposure; a certain amount of sacrifice has to be accepted in order to achieve the photographic objective at the time. I think that working in RAW is a big factor, and a small but significant amount of detail can often be recovered with a little patience and experimentation. Originally posted by WMBP But in practice, what I really need isn't to push my exposures to the right - I need a camera with greater dynamic range! Ah! Now isn't that just the truth. We're all chained to the limiting factors of currently available technology. Another five years will see enormous changes, and another ten will, I suggest, be very much a different world. So all things considered, these are rather exciting times. Oh, and if I've come across as a little bit too strongly opinionated, I apologize.