Author Topic: Wrong HDR bracketing exposures  (Read 5122 times)

janjan

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Wrong HDR bracketing exposures
« on: November 25, 2014, 08:22:34 PM »
Hi,
ML may produced images with SAME exposure instead of varying exposure.
e.g I may get the following bracketed shots sequence:
1) A:5.6, T:1/200,   ISO:100
2) A:5.6, T:1/400,   ISO:200
3) A:5.6, T:1/800,   ISO:400
4) A:5.6, T:1/1600, ISO:800
5) A:5.6, T:1/3200, ISO:1600
The ISO is changing and as a result all exposures are the same

I have a Canon 600D and I ma using the latest nightly build.
I did not have this issue with the ML stable release from 2011 (or was it 2012?)

I use the auto detection mode to decide how many exposure to take.
My camera settings:
Manual mode for A/T, as recommended
I sometimes set constant ISO and sometimes leave it in auto.

ML Settings:
Bracket Type: Exposure (Tv,Ae)
Frames: Auto Detect

Is this a bug?
Am I setting something wrong?
Does it only work in manual mode (well, from my experience it does not really work even in manual mode)

Any help would be appreciated.

Dan


garry23

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Re: Wrong HDr bracketing exposures
« Reply #1 on: November 25, 2014, 10:05:48 PM »
Don't use Auto ISO.  ;)

janjan

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Re: Wrong HDR bracketing exposures
« Reply #2 on: November 26, 2014, 08:24:44 AM »
This is not the way it is supposed to work even with auto ISO.

russellsnr

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Re: Wrong HDR bracketing exposures
« Reply #3 on: November 26, 2014, 01:07:05 PM »
Hi, Also use a 600D and never have a problem.
Normaly take 5 exposures 1 stop apart in the 0+++ option first exposure 2 stops under ie, if I have 1/125 at F8 will set the first at 1/500 at F8 2nd at 1/250 3rd at 1/125 4th at 1/60 5th at 1/30
NEVER change ISO from 180 unless really dark. and NEVER touch the Apt.
Have you got ISO shifting OFF?
If the problem goes on can I suggest you go into Prefs-Config files-Restore ML defaults and see what happens after you setup bracketing again.

janjan

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Re: Wrong HDR bracketing exposures
« Reply #4 on: November 26, 2014, 02:15:48 PM »
Thanks for the reply,

In your flow you are not using the auto feature, perhaps this is why you do not detect any problems.
You are using 5 stops always, am I correct?
You intentionally start with -2 under exposure and take 5 shots of +1 each, correct?
If you do then why did you go for the 0+++ option and not the 0+_ starting with normal exposure? 

You never change aperture? What exactly do you mean?

In my settings I have ISO shifting OFF and I want to use the auto option for the number of exposures to shoot.
I shall try resetting the preferences and see if it solves it.

russellsnr

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Re: Wrong HDR bracketing exposures
« Reply #5 on: November 26, 2014, 02:38:24 PM »
Hi, OK what I mean when I say I do not change apt I am saying for that bracket of shots I will change the app if and when I take another series of images if it needs to be changed for the DOF.
I use the 0+++ option as I found that when it comes to PP I no that every set of images will be in that sequence, I did try the 0-+--++ but to me that sequence is to mixed up I want an even work flow and found that useing the 0+++ kept everything in order.
As I said in the first reply I normaly use  5 exposures 1 stop apart but obviously if the situation arises that I need more I will take more, most people who do HDR say that actually on most occassions 3 exposures should be enough for most scenes.
I will try your way with the system set to auto and see what happens, maybe not today but ASAP.

janjan

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Re: Wrong HDR bracketing exposures
« Reply #6 on: November 26, 2014, 03:01:56 PM »
Thanks,
I used to shoot 3 exposure or 5 but I am trying to use the auto method because in some situations you may not always know which 5 exposures you really need.
e.g. it may be that you need -1 0 +1 +2 +3.
Indeed I found that in some shots the auto feature gave me unbalanced 7 exposures from -4 tp +2

I just tries it again:
When I set auto ISO the some shots have the same over all same exposure values with different ISO.
When I set ISO to manual as well the results were as expected.
As the user guide says, this feature works best in manual mode and it should add that ISO should be set to manual as well.

If you give auto a try please, could you test with auto and manual ISO?




garry23

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Re: Wrong HDR bracketing exposures
« Reply #7 on: November 26, 2014, 06:57:11 PM »
Just to complete our little e-conversation', as I said above, onlt use a fixed ISO with manual exposure set.

I find the auto-bracketing is robust and adequately covers the highlights end.

Where I find it 'lacking' is the shadow end, ie it will stop bracketing too soon for my taste.

To overcome this, I meter for the shadows and start my auto bracketing from there.

One thought I had was to introduce an ETTL (sic) offset variable, is that the auto bracketing algorithm uses to ensure the shadow end is x Ev offset. x being the ETTL offset. As I say, just an idea, although by metering for the shadows as your base bracket you dont really need the ETTL offset.

Finally, these days, if I do use bracketing (I mainly use dual-ISO) I also find myself simply creating a 'flat' 32-bit TIFF in LR, ie not really using HDR toning, as LR workd great in 32-bit space, ie +/- 10EV to play with.

janjan

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Re: Wrong HDR bracketing exposures
« Reply #8 on: November 27, 2014, 08:01:10 AM »
I also found that the auto feature is lacking in the shadows.
I shall try metering for the shadows instead of using exposure compensation.

Two things which are still not clear to me:
1. Is what I described; getting the same exposure values when using auto expose bracketing with auto ISO, a bug or is this how it is supposed to work by whoever wrote the code?
If it is a bug I will report it hoping someone will look into it.

2. When not using the auto exposure bracketing feature, do I still need to use fully manual controls, Av,Tv & ISO?

Did you ask for a feature enhancement concerning the shadows issue in auto mode?

And lastly, thanks for sharing you flow.
I use HDR Efex Pro for Photomatix. I find it more flexibly and versatile then ACR.


garry23

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Re: Wrong HDR bracketing exposures
« Reply #9 on: November 27, 2014, 02:27:45 PM »
@janjan

Regarding auto-ISO, just don't use it when bracketing. With Auto ISO I believe the camera's exposure system will be 'fighting' the ML bracketing algorithms. Simply don't use Auto ISO. Use a fixed ISO.

So it's not a bug, it's simply how auto ISO works.

I have not requested a feature enhancement as Alex and the devs have a lot on their plate and by placing the base exposure for the shadows I get what I need.

Try the Photomatix 32 bit plugin in LR, it really works well.

janjan

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Re: Wrong HDR bracketing exposures
« Reply #10 on: November 27, 2014, 02:47:57 PM »
Thank you for that.

russellsnr

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Re: Wrong HDR bracketing exposures
« Reply #11 on: November 27, 2014, 03:42:53 PM »
 Hi, I did a quick test today in all the modes at 1 stop intervals I could think of and all came up with exposures from lights to darks the only thing that I was not really happy with was the auto exposure option, it did exposures of different values but for the same scene shooting from inside to out through a window at F8 with the first exposure taken for the highlighted window it took 10 exposures when really only 5 would have been enough.

garry23

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Re: Wrong HDR bracketing exposures
« Reply #12 on: November 27, 2014, 04:20:23 PM »
@russellsnr

You most probably don't need a 1Ev increment, try 1.5 or 2 to lower the image count.

Also if you rebracket a scene when the exposure is changing because of sun and cloud interactions, you may well see the auto bracket sequences different between shoots.


russellsnr

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Re: Wrong HDR bracketing exposures
« Reply #13 on: November 27, 2014, 06:06:42 PM »
Hi, Yes Garry see that point but like you do not really use the auto bracket feature, rather use my hand held meter and use that reading as a base.
A little off topic!!
Do you no if it is possible to use ML via a pad? Nexus etc etc.
I have DSLR Controller on the pad but not as many options as in ML.
Thanks
Russ

garry23

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Re: Wrong HDR bracketing exposures
« Reply #14 on: November 27, 2014, 06:27:47 PM »
Russ

I do use the auto bracket feature, but choose the base exposure part of my scene as the area that is the 'darkest' where I wish to see detail, ie I do a spot meter there from the camera or use my Sekonic 1 deg spot meter.

What I do find is that the dual ISO covers a lot of my wider DR needs. Hence I don't do much bracketing these days, eg only in high DR environments such as churches etc.

I have a CamRanger running from my iPad, but I don't think there is a tablet or iPad based interface for ML yet, but I believe some are working on this.

Cheers

Garry