PDA

View Full Version : Some HDRI questions


D-e-W
05-17-2010, 09:47 AM
Hey!

I am doing some IBL in maya and have finally gone out to take my own images.
Done the IBL thing in maya several times but never with my own images.
I used a Canon 30D camera and got .cr2 images that have a 16-bit color space.

Now I have never stitched or created my own HDR images and searched around here on the forum to find answers but couldn't really figure this out and I don't have time to buy the HDR Handbook :P

So how many images do I need?
I mean if I combine two images with different exposures I should get a 32-bit images right?
16 + 16 = 32 is what my mind is thinking but after reading a few threads here I have understood that most of you guys use more images.

Why is that necessary?

And one more thing. I am probably going to blur the image to make it easier on the flickering when I render my 3d so how well do the images have to be aligned? I didnt have a tripod when shooting my chromeball so the images aren't perfect...
Sorry for beeing a noob :P

DeW

D-e-W
05-17-2010, 12:47 PM
Okay skip the post above.
I have gone through that and made a few HDR files but one of my files gets really screwed up by the aligning process.
SO I need to align the images myself but I cant do this in photoshop since it cant handle the rawfiles.

Is there any software that will let me align raw files without touching the image color info?

DeW

Guacomodo
05-18-2010, 04:43 PM
Use Canon Photo Professional to convert those files to 16bit tiff files. Most programs should be able to read them.

MisterS
05-21-2010, 12:49 PM
You should buy the HDRI handbook, it's a wealth of information.

you should aim to shoot exposures with 1 or 2 stops between them - or more if you want a smoother result.

the number of frames is determined by range of brightness values in your shot.

To work out what you need to do, switch to spot metering on your camera, stick it in AV mode.

Meter on the darkest part of your scene (without exposure compensation), write the shutter speed down - this is your first shot that you need to take when in manual mode. then meter on the brightest part of your scene, write this down - this is going to be the other end of the exposures.

now take a shot for every stop between these shutter speeds (or take more to get a better result)

This is written in more detail in that book. Can't rate it enough - has all you need to know.

D-e-W
05-21-2010, 12:53 PM
Thanx for your replies guys! :)

To bad we already have gone through production.
Should have read up some more on the acctual process when tkaing the images.
I will definatley buy that book :)

Anyway I will try the tiff thing and see where I get. Seems right no as if my images are a bit low on light butt im sure i can figure it out. Otherwise Ill just post again :)

Cheers!
Martin

sundialsvc4
05-22-2010, 12:13 AM
Most professional-grade digital cameras support "auto-bracket" modes which will rapidly take a group of exposures covering a specified gamut of settings. All of the images will be accompanied by metadata containing all of the relevant parameters.

I still shoot a gray-card, a gray-ball and a white-ball in any setting, before and after each group of shots (to allow for changes in light during that time).

D-e-W
05-22-2010, 02:36 PM
I will definatley remember that.
Havent had time to look at this problem for a few days now but I went by the library and they are going to get the HDRI handbook for me :)
Ill definatley buy it when I get the money though! :)


Thanx again
DeW

CGTalk Moderation
05-22-2010, 02:36 PM
This thread has been automatically closed as it remained inactive for 12 months. If you wish to continue the discussion, please create a new thread in the appropriate forum.