Photomatix and ACR - ACR cropping a little??

Hi guys,

I have tried searching for a relevant post but cant seem to find anything.
Basically I blend multiple exposures and bits of an HDR (made out of the same exposures) into one image.
For some reason the HDR created with Photomatix appears to have approx an extra 10 pixels on all sides. Each of the separate rawfiles are pretty much identical (all tripod shot) but the HDR created from them definitely has extra information?

I'm guessing that Adobe Camera RAW when developing the image "cuts off" this extra data but Photomatix sees and uses it (I tell PM to use the RAW files directly)?

This is a slight problem for me as when I blend in Photoshop the HDR image obviously isnt the same size.

Has anyone come across the same issue? I guess I can develop each of the RAWs into tiffs and then use the tiffs in Photomatix to get round the problem but just wondered why this is happening?

Any info most welcome!

Cheers.

A major part of the conversion from RAW to a rendered RGB image is a process called demosaicing. In a RAW each pixel carries data for only one color channel, but in a color image each pixel has data for all three channels. During demosaicing the immediate neighborhood of each pixel is inspected and data for the two "missing" channels is interpolated. However, pixels at or near the edge of the sensor have incomplete neighborhoods and the interpolation can be faulty. For this reason Canon (camera or DPP) and ACR/LR discard those pixels. Other converters, including those that are based on the DCRaw conversion engine (an Open Source converter used by a several dozen applications) retain all the pixels.

Thanks Tzalman. I had heard about demosaicing but hadnt really studied any further. Your explanation makes good sense. Guess I will be converting my RAWs to tiffs before working on them further.

Thanks again for the help.
Cheers.

rusty.jg wrote in post #11543351
Thanks Tzalman. I had heard about demosaicing but hadnt really studied any further. Your explanation makes good sense. Guess I will be converting my RAWs to tiffs before working on them further.

Thanks again for the help.
Cheers.

That's a good idea because the RAW conversion done by Photomatix is rather rudimentary. You can do a much better job with ACR.

Yes it does. I remember a thread from 1-3 years ago that talked about it, and there was a tool to change it. It may have worked on a DNG file, i'm not sure.

Blending from a TIFF is a better idea anyway.