[WIP] Exposure Value Calculator for HDRI (EVCalc)

Posting this here, in case anyone else will find it useful :)

For the past day I've been working on a little piece of software that calculates the required camera settings to effectively capture HDR scenes, based on your camera's f-stop, ISO, and shutter speed.

Here's a quick screenshot of the interface below, as well as a link to the current version:

Download (Requires .NET 4.0)

http://dl.dropbox.com/u/2028/EV%20Ca...screenshot.png

Code:

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Highlights = 0.031250s @ ISO100, f/8.00 (11.00EV)
Midtones  = 0.100000s @ ISO100, f/8.00 (9.32EV)
Shadows    = 1.500000s @ ISO100, f/8.00 (5.42EV)

Highlights to Midtones = 1.68EV
Midtones to Shadows    = 3.90EV
        Warning: Exceeded tonal threshold of 2.00EV.

Tonal threshold exceeded between midtones and shadows, calculating necessary exposure(s)...
Exposing for the midtones and shadows...
        Midtone to Shadow Span        = 3.90EV
        Using a tonal threshold      = 2.00EV
        Additional exposures required = 1
                7.32EV = (0.400535s)


Captured Dynamic Range = (8.00EV) + [(11.00EV) - (5.42EV)] = 13.58EV
Dynamic Range Increase = 69.75%

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In a nutshell, my program asks for the required settings to successfully capture the highlights, midtones, and shadows of a scene. It then calculates the relative exposure values (EVs) and prints back whether the camera's settings can grab all of the information, and if not, what additional exposures would be necessary, in case there is too large of an exposure gap between the highlights and midtones or the midtones and shadows :)

Questions, comments or suggestions for features are always welcomed and appreciated :up:

neat program. i am just not sure how one would use this instead of just taking the usual 3 shots then using HDR software like Photomatix HDR to tone map or HDR the pictures.
i understand this tries to give you proper values to set your camera to to get good HDR +/- EV settings but because most HDR softwares do so much already, how does one use this.
not only that but how does one use this when your not around a computer, your outside shooting pictures lol.

he needs to make it an iphone app now :)

no-no, android! :D

haha yes!

Thanks for the replies :)
As for a mobile application, since many phones can open Excel sheets now, an Excel version is a possible solution in the future :yepp:

Quote:

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Originally Posted by Lestat

neat program. i am just not sure how one would use this instead of just taking the usual 3 shots then using HDR software like Photomatix HDR to tone map or HDR the pictures.
i understand this tries to give you proper values to set your camera to to get good HDR +/- EV settings but because most HDR softwares do so much already, how does one use this.
not only that but how does one use this when your not around a computer, your outside shooting pictures lol.

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While Photomatix and other HDR programs merge multiple exposures together, what my program tells you is if your scene exceeds your camera's AEB range (which can happen quite often), by providing the settings to expose for the highlights and shadows, it will automatically provide and fill in the necessary middle exposures. Many HDR programs will "force" the provided exposures into merging, often resulting in high levels of noise in the shadows when there shouldn't be any.

EVCalc is less of a HDR merging software and more of a helper and optimizer in terms of the necessary exposures :)

Here's an example I did about a week back:

http://dl.dropbox.com/u/2028/Xtreme%...er_HDR_Web.jpg

The overall dynamic range was far greater than what my XTI could grab with it's ±2EV. I set the highlight exposure to 1/250s, midtones to 1/8s and the shadows to 1.6s. I thought this would be enough at the time since I was indeed exposing for each of the ranges.

After merging together, I noticed inconsistencies between the transitions of the midtones and highlights, which had odd hue and luminance changes, as well as a lack of contrast (can see seen on the white walls and trim in the above photo).

After plugging in the numbers I used into EVCalc, it did match what I was finding wrong in my merging process. I was about a full f-stop off in getting proper exposure between the midtones and highlights and could be corrected if I had one more shot at ~1/25s :)

ok can you say that in engrish pleez lol.

ok just read what i am saying, i am just trying to understand where the program can be used.

i see a use for RAW but nothing else.
you cant use this on site out in the field, you cant meter midtones and shadows, etc. without walking the entire frame with a light meter in your hand and documenting each exposure in each section of the frame to be shot.

i guess i am at a total loss as to how this is to be used.

I am standing out in a wonderful green field or a beautifil church... its impossible to use this program, see what i mean?
best i could do is get the best exposure i could with RAW and use this to maybe get me closer results using DPP or PS.

or am i thinking completely way too deep into this???
This is my lack of general knowledge and overly self taught snap shots doing everything the wrong way lol.

but i see what you are doing, but dont understand how to even remotely use this outside of a laptop, netbook, PDA or other device that can be carried with you while you shoot, and then stand there for 20 minutes trying to figure everything out.

i aint bashing it. man no way, you've done more than i could even think about doing, i just don't get it or its practical use outside of a studio

and as usual, wouldn't taking a lot more exposures help instead of the somewhat default of 3? it would be faster too than using the program even if u had it on ur phone.

Quote:

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Originally Posted by Lestat

i aint bashing it. man no way, you've done more than i could even think about doing, i just don't get it or its practical use outside of a studio

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No offense taken. I do realize the limited use of my program since it's currently tied down to Windows-based computers. I guess since I stick mostly to inside subjects, I forgot that there are people who shoot outside as well :p:

Quote:

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Originally Posted by ripken204

and as usual, wouldn't taking a lot more exposures help instead of the somewhat default of 3? it would be faster too than using the program even if u had it on ur phone.

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While more exposures will always result in better image quality, there's a point of diminishing returns since you can only cram so much information into the 16-bits of a TIFF or DNG.

Much of my program was influenced by this article on dynamic range by Guillermo Luijk. I guess I could say that my program is more of a mathematical than practical approach to doing HDR photography, providing the user the minimum number of shots needed.

My future plan is to allow importing of 16-bit TIFF or DNG files and do all of the blending in my program, creating an optimal 16-bit file with the full dynamic range embedded in it.