Why does Lightroom's "Auto" feature always change the exposure?

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LongTimeNikonUser Senior Member • Posts: 1,285
Why does Lightroom's "Auto" feature always change the exposure?

I use center-weighted auto exposure on my D3.  The results look fine.  I use Adobe Lightroom for post.  If I click on the AUTO button (LR Classic 9.4), the exposure is always changed.  Now I don't know what to trust, the Nikon's metering or Adobe's adjustments.

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michaeladawson Forum Pro • Posts: 14,538
Re: Why does Lightroom's "Auto" feature always change the exposure?
3

LongTimeNikonUser wrote:

I use center-weighted auto exposure on my D3. The results look fine. I use Adobe Lightroom for post. If I click on the AUTO button (LR Classic 9.4), the exposure is always changed. Now I don't know what to trust, the Nikon's metering or Adobe's adjustments.

I shoot RAW.  I let the camera meter and do it's thing with the exposure.  Sometimes I dial in +/- exposure comp.

In post I change the exposure myself 99% of the time.  Exposure, contrast, highlights, shadows, whites, blacks, etc.  Why do you think Adobe wouldn't when you select Auto?

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Mike Dawson

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Mark Scott Abeln
Mark Scott Abeln Forum Pro • Posts: 15,940
Adobe's Hidden Baseline Exposure Compensation

LongTimeNikonUser wrote:

I use center-weighted auto exposure on my D3. The results look fine. I use Adobe Lightroom for post. If I click on the AUTO button (LR Classic 9.4), the exposure is always changed. Now I don't know what to trust, the Nikon's metering or Adobe's adjustments.

Adobe software has what's called a 'hidden baseline exposure compensation', which is different for every model of camera, and may also vary with ISO. The purpose for this adjustment, presumably, is to take into account variations between cameras, particularly the amount of highlight headroom, and so making them look and act more like each other.

This article describes the issue and also shows how to determine your camera's hidden compensation:

https://www.rawdigger.com/howtouse/deriving-hidden-ble-compensation

There is one change, however. Adobe software used to name the various versions of Calibration Processes by year, and so while the article describes Process 2010, nowadays that is called Process Version 2. Instead of switching back to Process 2012 (or Version 3), just go back to the highest version in your software. The various versions are described by Adobe here:

https://helpx.adobe.com/camera-raw/using/process-versions.html

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md lucero Regular Member • Posts: 263
Re: Why does Lightroom's "Auto" feature always change the exposure?

I'm not a scientist, but here is my take.... You camera's light meter is calibrated to measure 18% gray (or a luminance of 18% gray). If you are using spot, center weighted, etc. it doesn't matter, whatever the type of method you use, it will come up with an 18% gray calculation. This is why it is so important to compensate for snow scenes, night photography, dark environments, etc....you would not want the meter to come up with an exposure that brightens up what should be a dark scene... I usually am my meter to what I would like to be the baseline of 18%, use ael (exposure lock) then recompose my image.

The math in LR's auto exposure is probably doing it's calculation based on a different calculation, just as it may often change the color temperature if done left done automatically..

Best,

Michael

hikerdoc Senior Member • Posts: 2,758
Re: Why does Lightroom's "Auto" feature always change the exposure?
1

It is supposed to be a reasonable guess starting point. I think it is setting white point, black point, pulling shadows, and preserving highlights. Sometimes it is right on, sometimes nowhere near what you are looking for. That is where the reset button comes in.

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ciaran33 Contributing Member • Posts: 636
Re: Why does Lightroom's "Auto" feature always change the exposure?

I often hit Auto just to see what it will suggest, but it always seem to sent Whites way to the right. Usually far to much for my liking. Nice to have the option, I suppose.

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OP LongTimeNikonUser Senior Member • Posts: 1,285
Re: Why does Lightroom's "Auto" feature always change the exposure?

michaeladawson wrote:

LongTimeNikonUser wrote:

I use center-weighted auto exposure on my D3. The results look fine. I use Adobe Lightroom for post. If I click on the AUTO button (LR Classic 9.4), the exposure is always changed. Now I don't know what to trust, the Nikon's metering or Adobe's adjustments.

I shoot RAW. I let the camera meter and do it's thing with the exposure. Sometimes I dial in +/- exposure comp.

In post I change the exposure myself 99% of the time. Exposure, contrast, highlights, shadows, whites, blacks, etc. Why do you think Adobe wouldn't when you select Auto?

I didn't think that Lightroom would always change the exposure. I'm just a bit surprised. I also shoot RAW. I used to shoot RAW+JPG, but now it's strictly RAW unless I need to get a photo out to people right away.

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michaeladawson Forum Pro • Posts: 14,538
Re: Why does Lightroom's "Auto" feature always change the exposure?
4

LongTimeNikonUser wrote:

I didn't think that Lightroom would always change the exposure. I'm just a bit surprised. I also shoot RAW. I used to shoot RAW+JPG, but now it's strictly RAW unless I need to get a photo out to people right away.

The camera is metering to get some sort of average middle gray value for the photo.  How it arrives at that value will depend on the metering mode, matrix or center weighted.

One of the things to realize about post-processing programs like LR is that the "Exposure" adjustment is not the same thing as the camera exposure.  Sure, it seems to behave similarly.  But it's really just a brightness adjustment.

When you press the "Auto" button in LR you're really not telling LR to override the camera's exposure metering.  You're telling LR to act like a human and post-process the photo to get the best looking result.  That means adjusting the overall brightness/exposure in combination with the highlights, shadows, whites, and blacks to get a good overall looking photo.  At least based on the algorithms that were programmed into it.

So when LR adjusts the exposure don't think of it as LR deciding the camera's metering was wrong.  The camera's metering was designed to capture the best "exposure" without blowing out highlights or severely underexposing shadows.  The work of post in LR is to move those bits of data around to get a pleasing looking photo.

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Mike Dawson

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TheGrilledCheese Forum Member • Posts: 84
Re: Why does Lightroom's "Auto" feature always change the exposure?

Lightroom doesn't use center-weighted metering like your camera. Use whichever method looks better to you. It's all about creative control!

NotASpeckOfCereal Senior Member • Posts: 1,571
Re: Why does Lightroom's "Auto" feature always change the exposure?

In addition to what's already been said:

When it adjusts all of the other values (black / white, shadow / highlight, contrast, color saturation, etc.), it is also changing luminescence values. That's going to change the base exposure value.

Try this:

  1. Without hitting AUTO, slide the exposure value up until the over-exposure indicator lights up. Note the exposure value, then reset to zero.
  2. Adjust a bunch of other things to taste (or hit AUTO), then see if the exposure over indicator lights up at the same place. It probably will not.

Another thing I found: if I find black/white points pre-AUTO (shift-doubleclick on slider handle), then hit AUTO and check the black/white points again, they may adjust to different values.

Also: when I hit AUTO, it often adjusts exposure, but not 100% of the time as you stated. Usually, but not always.

Chris

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michaeladawson Forum Pro • Posts: 14,538
Re: Why does Lightroom's "Auto" feature always change the exposure?

NotASpeckOfCereal wrote:

In addition to what's already been said:

When it adjusts all of the other values (black / white, shadow / highlight, contrast, color saturation, etc.), it is also changing luminescence values. That's going to change the base exposure value.

Sorry, I mean this very light-heartedly, but I can't help but comment.  I think you mean luminance values.  Luminescence is something entirely different.

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NotASpeckOfCereal Senior Member • Posts: 1,571
Re: Why does Lightroom's "Auto" feature always change the exposure?

michaeladawson wrote:

NotASpeckOfCereal wrote:

In addition to what's already been said:

When it adjusts all of the other values (black / white, shadow / highlight, contrast, color saturation, etc.), it is also changing luminescence values. That's going to change the base exposure value.

Sorry, I mean this very light-heartedly, but I can't help but comment. I think you mean luminance values. Luminescence is something entirely different.

Thanks Michael, yes, I meant luminance.

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OP LongTimeNikonUser Senior Member • Posts: 1,285
Re: Why does Lightroom's "Auto" feature always change the exposure?

michaeladawson wrote:

LongTimeNikonUser wrote:

I didn't think that Lightroom would always change the exposure. I'm just a bit surprised. I also shoot RAW. I used to shoot RAW+JPG, but now it's strictly RAW unless I need to get a photo out to people right away.

The camera is metering to get some sort of average middle gray value for the photo. How it arrives at that value will depend on the metering mode, matrix or center weighted.

One of the things to realize about post-processing programs like LR is that the "Exposure" adjustment is not the same thing as the camera exposure. Sure, it seems to behave similarly. But it's really just a brightness adjustment.

When you press the "Auto" button in LR you're really not telling LR to override the camera's exposure metering. You're telling LR to act like a human and post-process the photo to get the best looking result. That means adjusting the overall brightness/exposure in combination with the highlights, shadows, whites, and blacks to get a good overall looking photo. At least based on the algorithms that were programmed into it.

So when LR adjusts the exposure don't think of it as LR deciding the camera's metering was wrong. The camera's metering was designed to capture the best "exposure" without blowing out highlights or severely underexposing shadows. The work of post in LR is to move those bits of data around to get a pleasing looking photo.

Thank you for this lucid and helpful explanation.

Now I feel better about my Nikon D3.

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