[HDR-photo] xmp files

Sun Dec 10 21:05:28 EST 2006

Hi all,
I'm working on a "How to" book about HDR photography to be published '07. 
All my previous work from the film years and into the digital years is 
pretty useless so I've been doing lots of traveling and shooting. The 
majority of my days are filled with traveling, shooting, or writing.

My website is www.beforethecoffee.com but I'm saving the HDR images for the 
book.

I shoot a Nikon D2x and use a PC.

Ferrell McCollough

----- Original Message ----- 
From: "Jack Howard" <jackhowardphotography at gmail.com>
To: "High Dynamic Range Photography" <hdr-photo at hdr-photography.com>
Sent: Sunday, December 10, 2006 4:54 PM
Subject: Re: [HDR-photo] xmp files

> I'm working on some replies to these questions/comments, but first
> off, it might be nice for everyone to give a short introduction so we
> all know who's in the room, so to speak.
>
> I'm Jack Howard, Associate Editor for Popular Photography &
> Imaging/www.PopPhoto.com.
>
> I'm currently at work on the Photomatix User's Manual, and also on an
> eBook on various HDR softwares from different companies.
>
> I work primarily on Macs, though am very familiar with PCs. I shoot
> mostly Canon, but shoot with whatever camera needs to be
> reviewed/tested for the magazine.
>
> I live in New Jersey, and work in midtown Manhattan.
>
> My iChat screen name is baileyscotiadog.
>
> Jack Howard
>
>
>
>
>
> On 12/10/06, Ferrell McCollough <ferrellmc at comcast.net> wrote:
>>
>> Hello,
>>
>> I think xmp files for HDR images would be a benefit to the user.
>> Although PM includes in the file name the number of images and the 
>> starting
>> file, for example Set01HDRI5from_DSC2535.hdr,  it doesn't help us if we 
>> have
>> 5 bracketed images and only use 2 or 3 of the set.  An xmp file should 
>> list
>> the file name w/ extension, image size, exposure values, and EV steps.
>>
>> Some cameras, like Nikon have a max 1EV step when using AEB mode, so in
>> order to use AEB and get a +2EV and a -2EV sequence we need to shoot 5
>> images and delete or not include the +/-1EV images in the merging. I've
>> notified Nikon of the need for AEB of 5frames @ 2EV steps. Hopefully it's
>> just a firmware update. Other camera's like Pentax, Fuji and Olympus only
>> allow 3 frames at a max of 1EV step (except for the Fuji S3 Pro which 
>> allows
>> 2EV steps)
>>
>> Here's a typical Nikon AEB shoot sequence:
>> 5 images @ 1EV step:
>>
>> 5385.nef    0EV
>> 5386.nef    -2EV
>> 5387.nef    -1EV
>> 5388.nef    +1EV
>> 5389.nef    +2EV
>>
>> If I used 3 images of this 5 image set I'd like to know in the xmp file 
>> if
>> it was the 0EV, +1EV, -1EV, or the 0EV, +2EV, -2EV for example. Using all 
>> 5
>> images isn't necessary.
>>
>> Here is an example of xmp info in which the +/-2EV steps were used. It
>> includes the file names, sizes, exp and EV step.
>>
>> DSC5385.NEF    4320x2868    1/50sec - F/18    +/-0EV
>> DSC5386.NEF    4320x2868    1/200sec - F/18    -2EV
>> DSC5389.NEF    4320x2868    1/13sec - F/18    +2EV
>>
>>
>> Canon on the other hand is able to shoot 3 frames @ 2EV steps in AEB 
>> mode.
>> For a high contrast scene in which +/-4EV is needed, the photographer can
>> dial in -2EV then shoot AEB for a sequence of -4EV, -2EV, 0EV. Then dial 
>> in
>> +2EV and shoot another AEB set for a sequence of +4EV, +2EV, 0EV. The end
>> result is a very high dynamic range capture but there are two images that
>> are 0EV. One must be deleted or not used in the merging. It would be nice 
>> to
>> know, especially in ghost analysis, which 0EV was used.
>>
>> So as you can see present camera technology is designed for small
>> incremental bracketing or limited bracketing. This is good for choosing 
>> the
>> best single shot of the scene but not for HDR merging. So as we shoot we
>> capture more images than we need, some get deleted, and some become part 
>> of
>> the merging. An xmp file will show us which ones were part of the 
>> merging.
>>
>> Shooting in AEB mode is the superior method as it doesn't require 
>> touching
>> the camera between images. The less you touch the camera the less the 
>> chance
>> of camera movement. Also AEB allows for continuous shooting at high fps.
>> Shooting in manual, or using exposure compensation requires dialing-in 
>> each
>> exposure and unless the camera is tethered there is a chance of movement
>> even if on a pixel level. Shooting in manual also has a slight 
>> disadvantage
>> of not including EVsteps in the Raw xmp file, just f-stop and shutter 
>> speed.
>>
>> With today's limititions in DR of our monitors, HDR images are a stepping
>> stone to the final tone mapped image. How much we need to open and view 
>> our
>> HDR images will be limited, it's mostly archived information once the 
>> tone
>> mapping is completed. If we decide later the tone mapped image is not to 
>> our
>> liking we can begin with the HDR file again or begin with the raw files
>> again. The tone mapping data would be very valuable either with the hdr 
>> or
>> as a separate file like PM has now.
>>
>> I believe we should always save our original RAW files, especially the 
>> 0EV
>> for that single shot metered exposure of the scene. I think it would be 
>> nice
>> but somewhat redundant if the HDR image contained info that the Raw file
>> has, white balance, ISO, Color Mode, Focal length, lens used, etc. It
>> doesn't change between exposures so it's not critical. File size doesn't
>> change between images, but it's important to see if an hdr is derived 
>> from a
>> reduced image set, for speed of processing.
>>
>> On another note, I think it would be great if the HDR image had 
>> information
>> of the real world dynamic range captured expressed as EV range. I'd like 
>> to
>> know if the scene had a range of 6EV, 9EV or even 12EV. It would be 
>> valuable
>> in learning to associate a particular scene with a dynamic range. That 
>> would
>> then give us some insight into bracketing range.  Right now the only way 
>> to
>> learn the DR of a scene is to spot meter the scene and record the EV of 
>> the
>> darkest and lightest part of the scene or as most of us do, just wing it. 
>> Of
>> course the sun would have to be eliminated from the calculation, as
>> photographers we rarely want to expose for the sun's disc but only the 
>> blue
>> sky around it.
>>
>> So I think an xmp file should have:
>>
>> File names
>> File sizes
>> Shutter speeds & f-stops
>> EV's
>> Dynamic Range
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> _______________________________________________
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>> HDR-photo at hdr-photography.com
>> http://www.hdr-photography.com/mailman/listinfo/hdr-photo
>>
>>
>>
>
>
> -- 
> Jack Howard
> 732/682-7628
> www.sportsshooter.com/jackhoward
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