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05-02-2010, 09:01 AM   #1
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[langtitle=da]HDR billeder[/langtitle]

Hej
Jeg har et PENTAX K-X spejlreflekskamera. Jeg har lige hørt om HDR teknikken, og skulle afprøve dette på mit kamera i dag.

Hvorfor kan PENTAX K-X ikke gemme HDR-billeder i RAW-formatet (DNG-format), men kun i JPEG? Er dette noget der bliver muligt senere (firmware opdatering)?

Det er fint, at kameraet samler billederne og laver det om til et HDR-billede, men kan man ikke få kameraet til at gemme alle billederne som er taget for forskellig eksponeringer, så man selv kan samle det til et HDR-billede (hvilket er den forgangsmåde jeg har læst om på nettet)?


05-02-2010, 09:23 AM   #2
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Your question comes from not understanding HDR I think.

Let me try to explain.
Your camera has a HDR function, but will store LDR (Low DR) images as a result from HDR processing in JPEG.
Your computer display, your printer etc, are not capable of representing HDR images complete dynamic range.
Therefore the HDR image needs to be translated again to LDR (for instance in a JPEG file) before it can be printed or displayed.
It is the dynamic range processing technique (which needs all kinds of trics) that will give the typical HDR feeling of a picture (not your out of camera pictures).
My K-7 (and I assume your K-x) use flat compression, giving images with lots of detail in shadow and high light, but without any contrast.

Why not store in RAW?
RAW is a format that stores orignal sensor image data, that data is lost in this process, since it is about combining 3 images (3 raw files), compiling an HDR image and transforming this HDR image in an LDR result using Dynamic Range compression.

If the image was to be stored using the orginal HDR contect, not the resulting JPEG file, RAW would not be the target format (since the resulting image is not sensor data), but TIFF 16 bit, or even better the special HDR format.
RAW files do not have the extra DR resolution capability that TIFF 16 or HDR files have.
There is a special HDR file format, using floating point numbers representing pixels, instead of the 8 bit / 16 bit integer formats used by JPEG or TIFF.

HDR is probably a much more complicated subject than initially seems.
If you are interested, there is a lot to read on the subject on the Internet.

- Bert
05-02-2010, 11:27 AM   #3
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It would still be nice if the camera (K7 as well) could store the RAW images used to produce the HDR photo. To the OP, if you want to do HDR, you are better off, In my opinion, to use bracketing and then a third party program to produce your HDR images. The In camera processing (on the K7) just doesn't do it for me. I know you are using the Kx but I think the processing is the same for HDR between the two.

05-03-2010, 11:26 AM   #4
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QuoteOriginally posted by JeffJS Quote
It would still be nice if the camera (K7 as well) could store the RAW images used to produce the HDR photo. To the OP, if you want to do HDR, you are better off, In my opinion, to use bracketing and then a third party program to produce your HDR images. The In camera processing (on the K7) just doesn't do it for me. I know you are using the Kx but I think the processing is the same for HDR between the two.

Jeg har kigget lidt på eksponeringsbracketing på mit kamera, men har ikke fået det helt til at køre endnu.

Hvis jeg har forstået det rigtigt, så laver kameraet et billede med normal eksponering, et billede med undereksponering og et billed med overeksponering. Er det rigtigt forstået? Kameraet gemmer de tre billeder i DNG-formatet.

Hvilket programmer kan man lave HDR-billeder med? Photoshop? Lightroom? Hvad er bedst at bruge?

Jeg har lige fundet dette program, hvor man kan lave et HDR-billede på baggrund af ens DNG-billeder.

Photomatix Pro 3
HDR photo software & plugin for Lightroom, Aperture & Photoshop - Tone Mapping, Exposure Fusion & HDR Imaging for photography


05-03-2010, 11:40 AM   #5
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There are probably a dozen software programs that will turn bracketed photos into a large HDR file.

I would never use the K7 onboard HDR feature after using specialized software. The software gives you so much more control over the final product than the K7 or KX version. I use photomatix by the way.

bracketed photos are the way to go and both the K10/k20/K7/KX have a fairly good implementation of it, better in some respects than some more popular cameras. There's an instructional article on Adorama about HDR cameras, and they give high marks to Pentax.

As to your question, locking RAW into an HDR file eliminates some of the artistic flexibility in using bracketed photos. For example, the files may need to aligned in a special way, ghost images may need to be removed, one or more of the files to be combined might need to be removed from the HDR attempt, etc.

Also, if there is a noise problem or some basic toning issues, it is better to remove these from the files before combining into an HDR.

best wishes
05-03-2010, 11:47 AM   #6
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I've had some fun shooting at high ISO, high shutter speed, and large aperture doing this handheld in camera for the hell of it.

Only got about 2 decent shots out of 30 attempts, but it's fun and a challenge!
05-03-2010, 11:58 AM   #7
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When i want HDR, i take just 1 RAW picture and PP it in 3 (or more) different exposure versions. In my favorite photo program (Photoshop CS4) i combine those files in 1 HDR image.
Working this way, you don't have to allign you're images and won't have any ghosting in the HDR result.

I also tried the K7 on-board HDR function, but it didn't produce the pictures i wanted. It is also extremely slow, after making a HDR shot, you're cam is a rather long time not usable because it is processing.
05-03-2010, 12:06 PM   #8
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QuoteOriginally posted by Sakura Quote
When i want HDR, i take just 1 RAW picture and PP it in 3 (or more) different exposure versions. In my favorite photo program (Photoshop CS4) i combine those files in 1 HDR image.
Working this way, you don't have to allign you're images and won't have any ghosting in the HDR result.
Let's see samples. It is hard to evaluate a technique that is offered as an equivalent or better without seeing the results you have obtained.

woof!

05-03-2010, 12:50 PM   #9
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QuoteOriginally posted by Sakura Quote
When i want HDR, i take just 1 RAW picture and PP it in 3 (or more) different exposure versions. In my favorite photo program (Photoshop CS4) i combine those files in 1 HDR image.
Working this way, you don't have to allign you're images and won't have any ghosting in the HDR result.

I also tried the K7 on-board HDR function, but it didn't produce the pictures i wanted. It is also extremely slow, after making a HDR shot, you're cam is a rather long time not usable because it is processing.
How do you combine them in CS?
05-04-2010, 11:26 AM   #10
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Hvordan sætter jeg eksponeringsbracketing i kameraet, så jeg kan lave et HDR-billede?
05-04-2010, 11:51 AM   #11
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Since you should use a tripod anyway, you should just do the metering manually as 3 or 5 shots.

Also, I would adjust the SHUTTER SPEED to bracket, and not the aperture. If you change the aperture, you're changing the depth of field. This doesn't really matter for scenic shots focused to infinity, but for other types of shots, changing the aperture may hurt you.
05-04-2010, 12:55 PM   #12
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QuoteOriginally posted by nph12 Quote
Hvordan sætter jeg eksponeringsbracketing i kameraet, så jeg kan lave et HDR-billede?
I don't have the KX but the K200D with probably a different menu structure. I get to the Auto bracketing function trough the FN button and then to the different photo modes like continues shooting or single shot and of course Auto bracketing. Trough the menu button and digging a bit in the menu I am able to control the amount of ev. compensation that is applied over all the three shots one is able to take with Auto bracketing. You should be able to find how this works in your manual. Otherwise you can use Ira his suggestion and do it manually which gives you more direct control.
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