Normalized tonemapping for multiple hdr images?

Panfoto

Hi,

Been lurking for a couple of months now but this is driving me batty. Batty enough to register <gasp>.

I have a couple dozen HDR images that I'd like to tonemap into LDR. I'm using linux with pfstools and qtpfsgui. When I tonemap the images it seems to compress the dynamic range, err, dynamically. These shots are going into a panorama and it looks pretty bad when the dark areas of one frame is lighter than its neighbor.

A bit of background: I'm new to both processing hdr images and panorama stitching. I tried hugin with the hdr files but they slow it down to a crawl. I also can't seem to get it to compress the dynamic range to display on a monitor.

I figure there are 4 possible things I'm doing wrong

1) creating the hdr files improperly
2) not grokking tonemapping
3) using the wrong tools for the job
4) everything

Any suggestions?

Snoleopard

A couple of things, since you did not post any samples. Try stitching pano before tonemapping once they are hdr images, or stitch each group of exposures then make them a hdr then tonemap. Also tonemapping will accentuate things like vignetting, you need to clear up any vignetting before stitching and before tonemapping. Without seeing samples or more details it is pretty tough to help out.

Alan

Zeus1

You should really buy the book The HDRI Handbook: High Dynamic Range Imaging for Photographers and CG Artists +DVD by Christian Bloch.
http://www.amazon.com/s/ref=nb_ss_gw/102-2662557-8908918?url=search-alias%3Daps&field-keywords=bloch+hdri&x=0&y=0

It's the "bible" of HDRI and tonemapping. He includes a large section on making pano's using tonemapping.

Another good book is Complete Guide to High Dynamic Range Digital Photography (A Lark Photography Book) by Ferrell McCollough
http://www.amazon.com/Complete-Guide-Dynamic-Digital-Photography/dp/1600591965/ref=pd_bbs_sr_1?ie=UTF8&s=books&qid=1220613080&sr=8-1

Panfoto

Alan,

I'll try to post 2 adjacent shots tomorrow, I just got back from out of town and I'm exhausted. I've definitely got some geometric distortion to fix up before the final stitching (I angled the camera up a bit), but right now I'm just trying to get the merge and stitch process ironed out.

Zeus1,

Thanks for the links. That first one looks especially interesting. I think I'm going to have to check it out!

Panfoto

Ok, I've attached an image that shows 2 adjacent shots. There's obviously other issues with them but right now I'm just trying to get the two consistent hdr images down to ldr in a consistent manner. If you look at the worn road and the shadow of the tree to the right you'll see what I'm talking about. I'm assuming this is happening because there's more highlights in the first shot and more shadows in the second shot.

Any ideas?

Snoleopard

You should really stitch the exposures then tonemap, not try and tonemap them and then stitch. Also try using the smartblend to do the blending. Stitch each set of shots then load the stitched hdr and combine, then tonemap down to ldr.

Alan