Garyminor Loc: Raleigh, NC

This is in response to Dave Graham’s post titled Tutorial: Welcome to Raw Exposure.
I have carefully read his post and understand the concept of extra raw-accessible dynamic range (ERADR).
Note: The following discussion is based on a fixed ISO.

There are some statements that are completely accurate.

Basically, he's right. If you need maximum dynamic range, then expose as far to the right as you can, without exceeding the highest range of the sensor (blowing out the highlights).

However, this comes at a cost. Dave is misleading when he writes

In reality, you would need an f/1.4 lens in order to expose one stop to the right, instead of an f/2.0 to expose normally.
Dave goes on to write:

In reality, you give up one stop of exposure (illumination) for every stop that you move the exposure to the right.

This is not only wrong, but the reverse is true. You need one stop slower shutter speed when you move the histogram one stop to the right.

Dave's advice is good if you need to bring out data from the shadows.
If you have a low key (black cat in a coal bin) scene, it's a good deal to EBTR and give up shutter speed or depth of focus to gain shadow detail.

However, if you have a low dynamic range scene, with midtones in zone V, then it may be better to use normal exposure, rather than give up shutter speed or depth of focus.

Keep in mind, this is based on fixed ISO, adjusting exposure as necessary. If you want to vary ISO in order to EBTR, then that is a discussion for another day.

Please don't consider this as an attack on Dave. I'm just stating the facts as I see them. Any comments (positive or negative) are welcome.

Gary Minor

Rongnongno Loc: FL

Negative comment:

Why not post this in the relevant thread then?

big-guy Loc: Peterborough Ontario Canada

Please re-read the original quote and you will see that he says the same thing you do. By cutting the shutter speed in half, as he says, you slow the shutter speed, as you say, by 1 stop regardless of who or how it is said.

***Addendum*** - just re-read my post and realized that technically, cutting the SS in half speeds up the exposure, BUT many, including yours truly, mistakenly use the term to mean the exposure and not SS. Mea Culpa

As with all rules there are times to implement and times to use another rule. In a high dynamic range scene then ETTR or HDR are fine tools to use. In a low dynamic range scene a standard exposure is fine to use. And on the flip side, sometimes creative license lets us break a rule for a totally different effect and as we all know, sometimes a dramatic failure too.

Also, to clarify, EBTR, you mean expose beyond the right? If that is true then highlights will be clipped and your post loses credibility. I think you meant ETTR, expose to the right.

Garyminor Loc: Raleigh, NC

I considered that. The original thread was a bit old. I thought it was better to start a new thread.
I'm new to forums so I have some learning to do. I'll keep your suggestion in mind.

As I said, all comments are welcome.

Garyminor Loc: Raleigh, NC

We agree that the shutter speed needs to be slowed, but his example implies a faster shutter speed.

This says that you can go from 1/100 sec with metered exposure, to 1/200 with EBTR, and therefore gaining the ability of handholding a 200 mm lens. This is opposite from what really happens. With EBTR you need to change shutter speed to 1/50 to get the added exposure.

Nikonian72 Loc: Chico CA

Part of the problem is the mis-use of the term 'shutter speed' rather than the correct term 'shutter duration'. Camera shutters do not change speed, but the time duration between leading shutter and trailing shutter can be increased or decreased. A shutter duration of 1/100-sec is twice as long as 1/200-sec (resulting in 1-stop increase exposure), and half as long as 1/50-sec (resulting in 1-stop decrease exposure).

Garyminor Loc: Raleigh, NC

It depends what you define as "the right". If this means the right of the true raw histogram, then you are correct. Anything beyond the right will be blown out and not recoverable.

The way I've seen the terms used is in relation to the camera display histogram. ETTR pushes the histogram data to the right of the display, where EBTR pushes the data beyond that, but still within the usable range of the sensor. In fact, this difference is what Dave calls extra raw-accessible dynamic range (ERADR), the primary topic of his original post.

My credibility is important to me. Part of that is to acknowledge my mistakes or misunderstanding. However, in this case, I think my credibility is intact.

Rongnongno Loc: FL

He monitors his 'old threads', as I am.

Garyminor Loc: Raleigh, NC

Although he used 'shutter speed' instead of 'shutter duration", I knew what he meant because he speaks of cutting the shutter speed in half to permit hand-holding with a longer lens. With EBTR, you loose the ability to hand hold a long lens, rather than gain this ability.

pego99

What are benifits? I prefer LGBLT.

rmalarz Loc: Tempe, Arizona

Nothing confusing about it. If you are at 1/100 and need to cut your shutter speed in half, it's 1/50.
--Bob

Dan De Lion Loc: Montana

Let’s forget f stops and shutter speed for the moment. Look at exposure in terms of letting in less or more light. For a given exposure situation, the more light you let hit the sensor the better (higher) the signal/noise ratio. That means you get better shadow detail. The limit on that effect is when you let in so much light the important highlights get blown out (they turn entirely white.)

F stops and shutter speed are two ways to let in more or less light.

The graph of the histogram should, almost all of the time, just touch the right side (highlights) and the left side (shadows.) Many cameras have a display mode that flashes blown-out highlights. Decreasing the amount of light hitting the sensor will eliminate those blow-outs.

SteveR Loc: Michigan

Negative comment.

And we know, that's all who matters.

rmalarz Loc: Tempe, Arizona

Dan, the histogram, displayed on the back of the camera, is the result of the internally processed jpg. It is not an accurate indication of the actual RAW exposure.
--Bob

freddusel Loc: Nashville

I am entirely new to digital photography having been a large format film user until I got too weak from cancer to manage my Linhof and Sinar. I am purchasing a Sony mirrorless A7rII. What is the "normal" dynamic range of the 42mp sensor in this camera?