Help with ETTR Please...

Pagman wrote in post #16639484
I am trying to get my head around and use ettr, i have been sellecting anything from +1/3-+1 ec, and today although using + 1 in poor weather and in sh priority, i was having to keep opening up my aperature till it reached 5.6 even though 400iso was selected by the camera, yet the meter kept saying - lo even with 125/sec sh speed, anyway when i processed my raws they where not showing any under exposure but just about spot on, my question is - why was lo showing even with ec of + 1 that created a good exposure.

Sorry for the stupid question just curious.

P.

Heya,

Meter your scene.
Take a photo and look at it's histogram. Or use liveview (equivalent) to see the current histogram.
Adjust your three exposure settings for your scene for a better histogram.
Further tweak via the EC correction to push it the last bit to the right.
Look at the histogram again after you take a photo.

Very best,

So you want the histogram as far right as possible without clipping? And of you can achieve this, does exposure need to be touched in post?

John from PA wrote in post #16640573
So right, saw ETTR and this 70 year old brain equated that to ETTL.

Sorry.

John, let's not get into politics...

jk

brettjrob wrote in post #16640089
EDIT: OK, I think I see what you're saying now. However, it assumes you're simply going to load the file into LR, jerk the exposure slider to -1.00 and be done with it. As long as you're willing to do a bit more work in PP (even as simple as using the Shadow/Fill Light slider after dialing in -1.00), ETTR should still give optimal image quality without impacting DR.

Yes, I am saying if you are moving your histogram to the right while shooting, and then back to the left in post (in addition to your normal post processing), you've clipped the 1 stop of dynamic range off the top of your sensor and decreased the dynamic range. Now, in reality it's a good thing that you do! There's very little to no data you want in that range (as you've clipped stuff to the right of the highlight peak in your histogram). The trade you are making (since nothing is free) is all of your shadows and blacks will be less noise prone because they are over exposed before your post processing.

So you overexpose with ettr to avoid noise in the shadows and pull it back down the same amount you ettr in camera?

Frodge wrote in post #16640855
So you overexpose with ettr to avoid noise in the shadows and pull it back down the same amount you ettr in camera?

Heya,

Slightly over-expose to get the highest amount of dynamic range (DR), as a method to do it with the least amount of perceivable noise. When you have noise and bring exposure down and smooth out noise with reduction, the image is cleaner while still having dynamic range because the light was there. If you under-expose and try to increase exposure and levels to make up for it, the noise amplifies and the image looks like a hot mess of grain from a web cam. Well, exaggerated, but pretty close.

This method is for making post processing of increasing dynamic range cleaner.

Very best,

Frodge wrote in post #16640855
So you overexpose with ettr to avoid noise in the shadows and pull it back down the same amount you ettr in camera?

Correct.

Pagman wrote in post #16639484
I am trying to get my head around and use ettr, i have been sellecting anything from +1/3-+1 ec, and today although using + 1 in poor weather and in sh priority, i was having to keep opening up my aperature till it reached 5.6 even though 400iso was selected by the camera, yet the meter kept saying - lo even with 125/sec sh speed, anyway when i processed my raws they where not showing any under exposure but just about spot on, my question is - why was lo showing even with ec of + 1 that created a good exposure.

Sorry for the stupid question just curious.

P.

Sometimes you just don't have enough light for the settings you are trying to use. They may call for f1/8 at 1/60, or even more in darker times needing exposures of 30 seconds or longer, or require a much higher ISO. Each shot has its own required exposure combination that it will take to get you proper exposure. It's all about how much light is there in the scene then selecting the right exposure for that particular scene, and ETTR simply means you are going to expose it just a little more than what a "proper" exposure calls for.

Frodge wrote in post #16640547
This is an interesting subject to me. Is there a video or tutorial on ettr and using the histogram? I would like to learn more in depth of how to get the perfect exposure.

In basic terms it's quite simple really, you just have to keep letting more light into the camera, or making the camera more sensitive to light, until you reach the limit that highlight detail you wish to retain is just short of the point where it will clip. Now we come to the factors that may complicate this.

The first problem is actually knowing how much light to let into the camera in the first place. The standard histogram displayed on the back of the camera, be that the total luminance or the colour channels is NOT based on the RAW data. It is actually based on the in camera JPEG image produced by converting the RAW data using the cameras settings. Almost all of the in camera processing settings will have some affect on the JPEG histogram, The major ones are the White Balance, and Picture Style as they have the largest affect on how the data is processed. Changing the picture style for Canon cameras changes the tone curve that is applied to the image, as well as altering saturation, contrast, noise reduction and sharpening. The application of the white balance will often push a colour channel that is not clipped in the RAW data into clipping when reduced to 8 bits. People shooting ETTR will often chose a neutral picture style and reduce the contrast and saturation to minimum. This is also where using "UniWhiBal" comes in, this custom WB setting ensures that all of the colour channels are treated equally. Unfortunately this also means that the image will have a strong green cast on the camera's LCD display. For many Canon cameras it is possible to install Magic Lantern which enables you to actually display the RAW histogram on the cameras LCD, so that you can then ensure that you are not actually going to blow data for any of the RAW colour channels.

So once you have a means of reliably checking where the RAW histogram is going to sit, now you can start to ETTR. The easiest way at first is to chimp your way there. Starting with the "normal" exposure simply check where the histogram sits, with a grey card filling the image that would be a peak just to the left of center. For an average scene it would be similar, but the peak will be quite a bit wider. Now add some plus EC and expose again, this will move the peak to the right. You would simply keep adding EC (or opening the aperture or lengthening the shutter duration in M mode). Eventually the peak will reach the right hand side of the histogram. This is usually the point to stop at. If you move any further to the right you will start to clip highlights. Now your image in the real world may have some highlights with no information in them anyway, reflections of the sun from chromium for example, or point light sources in a night scene. In this case you would probably want to keep going as it doesn't actually matter if these are clipped anyway. When you are learning this it is probably a good idea to keep taking exposures until you are a long way into the indicated clipping zone, so that you can learn what you can and can't do. If you run out of shutter speed or aperture before you get to the point of clipping, then what?

ISO, or as I said camera sensitivity. For CANON cameras at least this requires that you use only whole stop ISO values, and you do not use any of the extended ISO settings, so no L (ISO50) or H, H1, H2 etc. With canon cameras the additional noise added by increasing the ISO by one stop up to the limits mentioned will add less noise than you gain back from lowering the image brightness in the RAW converter. So if you cannot open the aperture any more for any reason, it is already wide open for example, or you need to keep f/8 for DoF reasons, and you cannot slow the shutter any more, because you will get unwanted motion blur for example, the Up the ISO.

So now you have done the first half of the ETTR system, now you have to process the image. ETTR is not a system for those who do not want to put any effort into processing the images afterwards. It is not that you cannot batch convert images, but for each set of conditions that you might shoot in there will generally be different processes needed and different optimisations still might be needed on an image by image basis. Your choice of RAW processor will also contribute to how you might expose for ETTR. DPP Canons own RAW processor is actually not very good for ETTR, as it is not optimised for extreme highlight recovery like some other processors are. Probably the two best RAW converters for ETTR, with the best highlight control are probably On-One C1 version 6 and Adobe's Process Version 2012 as included with LR4 onwards and ACR 8 with PSCS6 onwards. Personally I use LR4 for my conversions.

As someone said in another post processing an image that was shot ETTR is not simply a matter of pulling the exposure slider down by however many stops you boosted the exposure by. Although you may well pull down the Highlights and Midtones (which is effectively what the exposure slider in PV2012 controls), you will also often find that you can then boost the shadows and so effectively extend the range of tones that can be represented within the image. The important thing here is that because you exposed for the shadows as much as possible you are not actually boosting the shadow tones, just returning them to the level they were exposed at, so opening the shadows does not introduce additional noise to the image, and often the levels are lower than exposed anyway, which will reduce noise.

Hope this is of some help

Alan

To answer what I think is Pagman's issue. If you are dialing in +EC and are in Tv exposure mode with a fixed ISO once you have reached the maximum aperture the system cannot open up any further and so will indicate that you will underexpose according to what the lightmeter thinks the exposure +EC should be. So if you have +2 stops EC added to the "normal" exposure simply for ETTR purposes but due to aperture limitations you are 2 stops below what the meter would set, what will happen to the resultant image? It will be perfectly exposed as if you hadn't tried to do ETTR in the first place. Your resultant image will look fine, well unless you then try toing the post processing part of the ETTR process on the image.

Alan

Frodge wrote in post #16640547
This is an interesting subject to me. Is there a video or tutorial on ettr and using the histogram? I would like to learn more in depth of how to get the perfect exposure.

the HAMSTER thread

Thank you for all the comments on this, i get the use of the histogram and i view it after uploading my files into Lr, but with some of my picture taking being of suden subjects without the time to shoot -check the histogram then re -take, sutch as planes or bif shots.
My main line of questioning is relating to a scenario i experienced yesterday - the outdoor light was poor and i wanted to shoot a a family of deer but they were a little distance away so i was at max zoom, beacuse of the lens/lighting circumstances i had shoot wide open f5.6 and to avoid camera shake the best i could get was 125/sec even with my meter showing a lo exp warning, i was at 400Iso and had and EC of +1 stop.
I was under the impression that adding Exposure Compensation ontop of a fairly accurate meter reading was the act of ETTR, but after reading the HAMSTER Threads on here, they put more weight on Higher ISO being more to do with ETTR eg - using say 800Iso instead of 100Iso as long as enough light is reaching the sensor.
But how can this work under poor light where a wider aperature with high enough shutter speed is needed.


P.

Pagman wrote in post #16641357
But how can this work under poor light where a wider aperature with high enough shutter speed is needed.


P.

To some degree ETTR goes out the window when you are under conditions that max out your gears capability. If your lens is maxed out, and your shutter speed is as low as you can go without risking motion blur, then the only option is to raise ISO. When you are already maxing out the settings just to get a shot, overexposing to save some shadow detail is really a minor consideration.

Pagman wrote in post #16641357
But how can this work under poor light where a wider aperature with high enough shutter speed is needed.


P.

If you are already at your max aperture and slowest shutter speed you would like to use, your only other option is to bump ISO....

Lo exp warning basically means the settings you selected cannot meet your exposure need with EC set to +1.

kin2son wrote in post #16642065
If you are already at your max aperture and slowest shutter speed you would like to use, your only other option is to bump ISO....

Lo exp warning basically means the settings you selected cannot meet your exposure need with EC set to +1.

So that makes me wonder why the OPs camera was set to ISO 400 instead of increasing it. Perhaps a flash was on the hot shoe?

OP, if you are using the camera's auto exposure, it may overexpose or underexpose the scene, depending on the scene's dynamic range. So you will need to dial -EC when the scene has a wide dynamic range or +EC when the scene had a narrow dynamic range. Or none at all.