Exposure

Started 11 months ago | Questions
Trazan
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Exposure
11 months ago

I'm curious...how do you prefer to expose a e.g. "dark" scene when ISO is the difference? Do you expose it "full" (as long as highlights are not clipped) and reduce exposure in post, or adjust in camera on the spot?

Did anyone compare resulting noise from reducing exposure in camera vs doing it in post?

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VertigonA380
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Re: Exposure
In reply to Trazan, 11 months ago

It's too long to explain here but if you understand how a CMOS sensor handles brightness information, then you will expose to the right. As much as 50% of the information can be retained in the brightest stop all the way down until the shadows have minimal information retained in them. As you can see, it doesn't average exposure information like you might expect. This way you bring up the shadows in PP. This applies to low light exposure and not to middle exposure scenes. Look up "exposing to the right" and more than likely you will find some information.

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samjstern
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Re: Exposure
In reply to VertigonA380, 11 months ago

http://www.cambridgeincolour.com/tutorials/digital-exposure-techniques.htm

I gave you a link with some info to read.

ETTR is not always the correct way.

It is somewhat more involved than always exposing to the max.

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VertigonA380
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Re: Exposure
In reply to samjstern, 11 months ago

That link itself says:

Advantages:

  • Maximizes the number of tones recorded.
    Note: many recent digital SLR cameras have RAW files which record tones with 14-bit precision, so this is less of a factor than it used to be. It is highly unlikely that a RAW image will have insufficient tones (and become posterized) as long as it isn't grossly underexposed.

The OP is talking about low light, and exposing to the right is the right way in low light with RAW. If in doubt take an identical picture with different exposures and then pull out the shadows in PP. Crop in for noise and it will leave you with no doubt.

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Trazan
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Re: Exposure
In reply to VertigonA380, 11 months ago

VertigonA380 wrote:

The OP is talking about low light, and exposing to the right is the right way in low light with RAW. If in doubt take an identical picture with different exposures and then pull out the shadows in PP. Crop in for noise and it will leave you with no doubt.

How about if I'm convinced I don't need more dynamic range into shadows? From the link posted:

ETTR:
Requires more light than normal, and potentially a higher ISO speed
(which could mitigate any reduction in image noise from ETTR).

Exposing "dark":
Requires less light than normal, potentially enabling a lower ISO speed
(which would offset any increase in image noise).

So...exposing to the right/lighter areas gives less noise, but the use of higher ISO mitigates that.
Exposing darker results in more noise, but the use of lower ISO offsets this increase.

Assuming the resulting noise is equal I'd definitely chose ETTR. However I'm a bit unclear on whether plain reduction of exposure in post will equalize the gain/noise applied from higher ISO...

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Scott McMorrow
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Re: Exposure
In reply to Trazan, 11 months ago

Trazan wrote:

VertigonA380 wrote:

The OP is talking about low light, and exposing to the right is the right way in low light with RAW. If in doubt take an identical picture with different exposures and then pull out the shadows in PP. Crop in for noise and it will leave you with no doubt.

How about if I'm convinced I don't need more dynamic range into shadows? From the link posted:

ETTR:
Requires more light than normal, and potentially a higher ISO speed
(which could mitigate any reduction in image noise from ETTR).

Exposing "dark":
Requires less light than normal, potentially enabling a lower ISO speed
(which would offset any increase in image noise).

So...exposing to the right/lighter areas gives less noise, but the use of higher ISO mitigates that.
Exposing darker results in more noise, but the use of lower ISO offsets this increase.

Assuming the resulting noise is equal I'd definitely chose ETTR. However I'm a bit unclear on whether plain reduction of exposure in post will equalize the gain/noise applied from higher ISO...

Here's a simple rule of thumb to maximize dynamic range and noise for most recent Nikon sensors:

For D800/D6x0/D7x00/D5x00  Expose to the right up to ISO 1600.  Above that, leave ISO at 1600 and adjust in post.  If using AutoISO, set the maximum ISO to 1600 and be aware of this during your photography.  When AutoISO approaches 1600, be sure to use manual aperture and shutter speed settings to maintain better control of DOF and blur.

In general, ETTR in the ISO range where the sensor is using Analog gain.  Above that range, where digital gain is used, perform your final exposure adjustments in post processing.

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VertigonA380
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Re: Exposure
In reply to Trazan, 11 months ago

It's not intuitive but its about the way the sensor handles information, and how you can use that information to push more detail into the shadows, in low light. Unless you read about it, you won't understand it and unless you try it, you won't believe it. As for adjustment in camera vs post it, RAW does not hold extra unseen pixels, it just doesn't suffer the JPEG suppression.

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olakiril2
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Re: Exposure
In reply to VertigonA380, 11 months ago

VertigonA380 wrote:

It's not intuitive but its about the way the sensor handles information, and how you can use that information to push more detail into the shadows, in low light. Unless you read about it, you won't understand it and unless you try it, you won't believe it.

Shooting under dark conditions with moving subjects and unpredictable light, ETTR will often give me blurred shots and clipped highlights. That is why in dark conditions I ETTL, but that's just my shooting method.

ETTR is very useful for static subjects with a tripod and well thought metering.

As for adjustment in camera vs post it, RAW does not hold extra unseen pixels, it just doesn't suffer the JPEG suppression.

14bit vs 8bit makes a huge difference. Unless you try it, you won't believe it.

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InTheMist
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Re: Exposure
In reply to Trazan, 11 months ago

I usually just try to get it right in-camera. As I prefer my night scenes to be dark, I add negative exposure compensation.

I only use expose-to-the-right when I know the scene is going to be a exposure challenge.  Street lights are going to be blown, it's ok.

An advantage of not overexposing is that you keep a higher shutter speed.

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Trazan
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Re: Exposure
In reply to Scott McMorrow, 11 months ago

Scott McMorrow wrote:

Trazan wrote:

VertigonA380 wrote:

The OP is talking about low light, and exposing to the right is the right way in low light with RAW. If in doubt take an identical picture with different exposures and then pull out the shadows in PP. Crop in for noise and it will leave you with no doubt.

How about if I'm convinced I don't need more dynamic range into shadows? From the link posted:

ETTR:
Requires more light than normal, and potentially a higher ISO speed
(which could mitigate any reduction in image noise from ETTR).

Exposing "dark":
Requires less light than normal, potentially enabling a lower ISO speed
(which would offset any increase in image noise).

So...exposing to the right/lighter areas gives less noise, but the use of higher ISO mitigates that.
Exposing darker results in more noise, but the use of lower ISO offsets this increase.

Assuming the resulting noise is equal I'd definitely chose ETTR. However I'm a bit unclear on whether plain reduction of exposure in post will equalize the gain/noise applied from higher ISO...

Here's a simple rule of thumb to maximize dynamic range and noise for most recent Nikon sensors:

For D800/D6x0/D7x00/D5x00 Expose to the right up to ISO 1600. Above that, leave ISO at 1600 and adjust in post. If using AutoISO, set the maximum ISO to 1600 and be aware of this during your photography. When AutoISO approaches 1600, be sure to use manual aperture and shutter speed settings to maintain better control of DOF and blur.

In general, ETTR in the ISO range where the sensor is using Analog gain. Above that range, where digital gain is used, perform your final exposure adjustments in post processing.

Thanks, good to know! Disregarding dynamic range, could I apply the same guidelines to jpeg and video capture, noise wise?

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VertigonA380
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Re: Exposure
In reply to olakiril2, 11 months ago

I was referring to static objects and referring to the way information shifts during RAW processing and yes there is a massive difference for greater bit depths.

As for generally exposing a shot in low light, I like to bracket when possible. Getting it best in camera is a great idea although these days I PP anyway, getting it right just gives me more latitude in Photoshop.

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Scott McMorrow
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Re: Exposure
In reply to InTheMist, 11 months ago

InTheMist wrote:

An advantage of not overexposing is that you keep a higher shutter speed.

-

So then, it seems to me for the D800/D6x0 that the process which maximizes creative control, dynamic range and noise is:

  • manual control of shutter and aperture
  • Auto ISO to 1600
  • Exposure compensation to control highlight overexposure
  • let the camera underexpose once AutoISO hits 1600
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