Lowering the exposure of an HDR image

[stevepugh]

Hi all,

I am converting some high-range EXR frames into JPEGs and running into clipping/artifacting within the areas of the frame with highest exposure (blown out windows convert as cyan and pink pixels, for instance). Reducing exposure on the EXR frames in AfterEffects shows me that there is good data in there, but a straight conversion is no good.

Is there an easy way to reduce the exposure by a stop and a half or so within the command line using convert.exe? If I just use -level (which I'll try when I get to the office), will that preserve the data provided I have compiled with HDR support (which I have)? Many thanks!

Steve

[snibgo]

A "+level" might do what you want, or you might need a non-linear adjustment with gamma or "-sigmoidal-contrast".

("-level" currently clips but "+level" doesn't.)

I can't currently read EXR files, but if you create a floating-point tiff, I can take a look.

Code: Select all

convert in.exr -define quantum:format=floating-point -depth 32 out.tiff

[stevepugh]

I'll see what I can dig up, thanks much!

[fmw42]

I have some tonemapping scripts that work with HDR and EXR images, if you are using Linux/MacOSX or Windows/cygwin. They require HDRI compile of IM. see my link below. See for example the lamp on the desktop example in tonemap4.

If you post an example of one of your images, I can take a look at it and see about +level or +sigmoidal-contrast, etc.

I also have a script, xposure, that adjusts by stops. It uses -function polynomial.