Exposing to the right! An example

[billhercus]

It is a cold, windy spring day here so looking out of my attic window it came to me that I should experiment with 'exposing to the right.' After all, what else is a chap to do?

Two pictures below are from a 100% crop of two images taken within a few seconds from my attic window to the small ex fishing village which is about 4 miles away. The camera is on a tripod and the lens is a Sigma 100-300 f4 EX with a Sigma 1.4 TC at full stretch.
The top image was exposed at 1/160th and the botttom at 1/40th - both at f13.
Images were processed in RawShooter identically, except for exposure correction. There is no clipping in the longer exposure's histogram. Limited corrections were made in Photoshop to levels + some sharpening and sizing. Identical corrections were made although both images would require different processing to get the best results, I suspect.

Others will know far more than I about that!

From this simple experiment, the differences in these pictures are quite marked with the bottom (exposed to the right) image looking as if it has been through some noise reduction software (it hasn't).

I'd be interested in any guidance/comments here about how the bottom image should be processed for best effect or any general views on this technique.

[scottbergerphoto]

Shooting to the right is done to make sure that you capture the most data you can for an image. 1/2 the available data is in the far right stop of the histogram. It may be indistinguishable from a shot not done that way on a computer monitor. Your second shot is blurry, I suspect from the longer exposure on a shaky tripod? I don't think any of what you are seeing is do to shooting to the right.

[PacAce]

Originally Posted by billhercus

It is a cold, windy spring day here so looking out of my attic window it came to me that I should experiment with 'exposing to the right.' After all, what else is a chap to do?

Two pictures below are from a 100% crop of two images taken within a few seconds from my attic window to the small ex fishing village which is about 4 miles away. The camera is on a tripod and the lens is a Sigma 100-300 f4 EX with a Sigma 1.4 TC at full stretch.
The top image was exposed at 1/160th and the botttom at 1/40th - both at f13.
Images were processed in RawShooter identically, except for exposure correction. There is no clipping in the longer exposure's histogram. Limited corrections were made in Photoshop to levels + some sharpening and sizing. Identical corrections were made although both images would require different processing to get the best results, I suspect.

Others will know far more than I about that!

From this simple experiment, the differences in these pictures are quite marked with the bottom (exposed to the right) image looking as if it has been through some noise reduction software (it hasn't).

I'd be interested in any guidance/comments here about how the bottom image should be processed for best effect or any general views on this technique.

http://www.mayfieldghouse.freeserve....Exposetest.jpg

I'm curious to know how you determined the exposure to use for your first sample image. Was the shot properly exposed? The reason I'm asking is because the shot seems noisy and it looks like it might have been underexposed and corrected to get the right exposure.

The idea with "shooting to the right" is to use as much of the sensor's dynamic range as possible and that means making sure that the brightest part of the image is always at the right edge of the histogram without blowing out the highlight details that you would care about. Shooting to the right is most effective for low key shots where the bulk of the data is in the left half of the histogram. For normal scenes where there is data already near the right side of the histogram, shooting toward the right may not produce a noticeable change in the final image and, in fact, may risk blowing highlight details.

After you've taken a picture shot to the right, you now have to correct the exposure to get it where it's supposed to be, especially for low-key shots where it'll be obvious that the shot was over exposed. Doing this results in a cleaner image, expecially in the dark shadow areas.

[slin100]

Leo is right. The purpose of exposing to the right is to maximize dynamic range. RAW data is linear, so the data is even distributed throughout all stops. 1/2 of the data in the brightest stop is only true for JPGs due to gamma-encoding, which effectively redistributes bits into the brighter regions.

[scottbergerphoto]

Originally Posted by PacAce

The idea with "shooting to the right" is to use as much of the sensor's dynamic range as possible and that means making sure that the brightest part of the image is always at the right edge of the histogram without blowing out the highlight details that you would care about. Shooting to the right is most effective for low key shots where the bulk of the data is in the left half of the histogram. For normal scenes where there is data already near the right side of the histogram, shooting toward the right may not produce a noticeable change in the final image and, in fact, may risk blowing highlight details.

After you've taken a picture shot to the right, you now have to correct the exposure to get it where it's supposed to be, especially for low-key shots where it'll be obvious that the shot was over exposed. Doing this results in a cleaner image, expecially in the dark shadow areas.

Well said.

[scottbergerphoto]

Originally Posted by slin100

1/2 of the data in the brightest stop is only true for JPGs due to gamma-encoding, which effectively redistributes bits into the brighter regions.

According to this article http://www.luminous-landscape.com/tu...se-right.shtml , which has been cited numerous times as the reason for exposing to the right, that is not correct.

Home on The Dynamic Range
Let's assume for the purposes of illustration that a digital SLR has a dynamic range of 5 stops (it's usually closer to 6 stops, but let's not quibble). When working in RAW mode, which you should be, most cameras record a 12 bit image. (Yes, we say it's in 16 bit mode, but the reality is that it's only recording 12 bits in a 16 bit space. Better than 8, but not as good as a real 16 bits would be).

A 12 bit image is capable of recording 4,096 (2^12) discrete tonal values. One would think that therefore each F/Stop of the 5 stop range would be able to record some 850 (4096 / 5) of these steps. But, alas, this is not the case. The way that it really works is that the first (brightest) stop's worth of data contains 2048 of these steps — fully half of those available.
Why? Because CCD and CMOS chips are linear devices. And, of course, each F/Stop records half of the light of the previous one, and therefore half the remaining data space available. This little table tells the tale.

Within the first F/Stop, which contains the Brightest Tones 2048 levels available
Within the second F/Stop, which contains Bright Tones 1024 levels available
Within the third F/Stop, which contains the Mid-Tones 512 levels available
Within the fourth F/Stop, which contains Dark Tones 256 levels available
Within the fifth F/Stop, which contains the Darkest Tones 128 levels available

This realization carries with it a number of important lessons, the most important of them being that if you do not use the right-hand fifth of the histogram for recording some of your image you are in fact wasting fully half of the available encoding levels of your camera.
But, we all know (or at least should by now) that the worst sin in digital imaging is to blow out the highlights — just as it was when shooting slide film. Once they're blown (past the right-hand edge of the histogram) it's bye-bye data.
Quoted from the above linked article.

[PacAce]

To further illustrate what Scott posted above, I took a picture which has data that covers both ends of the range recorderable by a typical digital camera This is shown in first attachment below. I shot it in RAW and converted it as a standard TIFF image. What the converter did under the covers was apply a tone curve that more evenly distributed the image tones to what we're used to seeing. The data was also normalized from 12-bit to 16-bit so that the white point of the original 12-bit data from the camera lines up with the white point of the 16-bit format.

The 2nd attachment show you what the image from the camera looks like without any tone curve applied or normalized to 16-bit data. The white part of the image really isn't white because the maximum value you can specify with 12 bits falls short of the maximum value in 16 bit. You'll also note that you really can't make out the two dark tones on the left side of the image. That's because the data is all bunched up together.

Continued on next post....
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[PacAce]

To get the linear image to a more useful image, we would have to apply a tone curve similar to what the RAW processor applies when converting RAW to JPEG or TIFF. The first attachment show a sample tone curve that I appled to the linear image. It got the image close to what the RAW converter put out. And the 2nd attachment is the linear image after the tone curve was applied to it in PSCS.

BTW, if you go back to my Part 1 above and compare the histograms of image 1 and image 2 you can see the the two spikes on the right representing the bright tones are very close together whereas in the second image, they are pretty spead apart. This further illustrates what Scott posted above.
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[slin100]

Thanks for the excellent examples. I stand corrected regarding bit allocations.

[billhercus]

To be honest, I had assumed that a simple correction to exposure on the 'overexposed' image would be all that this technique requires but it seems that there is more to it.

To answer some of the questions which may explain the irregular quality of the pictures used, I submit the following:-

Exif for first shot:
(Second only difference is shutter speed)
100-300mm @ 420mm
1/160 sec, f/13
Mode: Av
Metering: Evaluative
ISO: 200
AF mode: AI Focus AF
Drive: Single frame shooting
White balance: Auto
Flash: Off
File size: 7,088KB
Image size: 3504 x 2336
Saturation: Normal
Sharpness: Normal
Contrast: Normal
Tone: Normal

The tripod is a Kenlock 3000 (about 20 years old) and I used a remote cord (but no mirror lockup) - the image is some 4 miles away.
I had left the focus on AI Focus AF which was not intended but I don't know if that would have an effect on this - can't think why.

For the first shot I used +0.35 EC in RSE which means exposure was not correct I know but would that not be within an acceptable tolerance?

For the exposed to the right image, I corrected -0.80 in RSE

The 'normal' image RSE histogram showed no detail in the right hand eigth of the display.
Capture sharpening by Photokit used High-Res and superfine edge
I used USM amount 22, radius 50 and threshold zero.
Output sharpening on Web and 800 pixel Superfine.
Any guidance on post processing errors will be gratefully received.

Scott's explanation from The Luminous Landscape was my original motivation for playing with this technique. There is obviously more to it than checking histogram, overexposing then correcting exposure in your RAW converter which is what I'd thought.
I shall certainly be taking more images 'to the right' bearing in mind comments here, as I feel sure this will be worth the effort, principally because of the pure logic of the case.

PacAce, I will study your reply at length ......

Once again, thanks for the distilled wisdom here!

[Harry Settle]

Excuse me, but I'm a little slow at some of this. When I read the "Shoot to the right", article at Luminous Landscape I assume that they are saying to shoot the picture exposed to the right of the histogram in order to ensure you have captured more detail in the low end. What you all seem to be doing here is adjusting a shot in post.

[PacAce]

Originally Posted by Harry Settle

Excuse me, but I'm a little slow at some of this. When I read the "Shoot to the right", article at Luminous Landscape I assume that they are saying to shoot the picture exposed to the right of the histogram in order to ensure you have captured more detail in the low end. What you all seem to be doing here is adjusting a shot in post.

Yes, you are correct. Shooting to the right does mean to set the exposure so the the data shows up as far right on the histogram as possible without blowing the highlights. And, as I mentioned in a previous post, this is most effective for dark or low-key scenes. However, after you have shot to the right, you just can't leave it that way or else the image will look over exposed. So, you'll need to post process the image to bring the exposre back in line with what it's supposed to be. In effect, in post processing, you will have to move the exposure to the left again.

[Harry Settle]

Thanks

[PacAce]

Here are a couple of examples of what shooting to the right does for you for low-key or dark subjects and scenes. All shots were taken at ISO 1600.

In the 1st attached image, A was shot using the correct exposure. B was shot 1 Stop under exposed. And C was shot to the right so that it was really over exposed as you can see from the bottom left image. The exposure for C was then corrected during RAW conversion processing. The image on the bottom right is the corrected image of C.

The 2nd attached image shows a 100% crop of A (the correctly exposed image), B (the under exposed image) after it was corrected in PSCS for the correct exposure, and C (shot to the right and corrected). As you can see high ISO noise is marginal in A, really bad in B and practically non-existent in C. Check out how silky smooth the background of C is.
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[PhotosGuy]

Great job, Leo!