Built-in HDR

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Offline littlejohn

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Built-in HDR
« on: 08 / August / 2008, 04:47:59 »
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Hi,

Recently I'm interested in HDR,
(High Dynamic Range (HDR) Photography in Photoshop CS2)
which is often used in an environment with high contrast.

I don't know the details about how the PhotoShop processes the pictures with different EV to one HDR picture,
but I guess that "RAW Average" is not enough to produce one.
CHDK supports Tv bracketing and RAW processing.
Is it possible to support built-in HDR, which selects a few files and generate a high-dynamic-range picture?

Thanks,
John

Ps. It's 8/8 (Father's Day in Taiwan), Happy Father's Day!  :xmas

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Offline dzsemx

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Re: Built-in HDR
« Reply #1 on: 08 / August / 2008, 06:53:02 »
already has been requested by hundreds of people...
first of all, photoshop hdr is 32 bits/channel without compressing it into a normal range image... usually it looks too dark...
after merge we use hightlight/shadow compression to make all details to viewable.
shadow/highlight compression needs complicated algorithms which needs a lot of time to code it...
it would require megabytes of memory but chdk can use few hundred kilobytes of memory, without interfering with the original operation system...
so for the moment it's not posible...

« Last Edit: 08 / August / 2008, 06:57:36 by dzsemx »

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Offline littlejohn

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Re: Built-in HDR
« Reply #2 on: 08 / August / 2008, 07:29:49 »
Thanks, I got it.

It sounds like an external memory algorithm is needed,
which uses limited memory and makes use of the space of disk (SD/SDHC card) to accomplish the task.
We don't have memory, but we have disks.
Any temporary data could be stored temporarily in the SD card,
the number of I/O should be minimized to obtain a fast running time.

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Offline dzsemx

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Re: Built-in HDR
« Reply #3 on: 08 / August / 2008, 07:37:52 »
yeah...it could be made using sd card, but a simple raw average takes more than a minute...


 

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