HDRi
- Thread starter surf
- Start date
Matt Grunau
Adobe Demigod
There is more to creating a HDR image than simply photographing a sphere, but you definately have the setup going right. HDR stand for High Dynamic Range, and it means just that. The file includes more info than an ordinary .jpg would (although you CAN use .jpg setup in you app to be used not only for reflection but for Radiosity), specifically in the regions of "exposure" if you will.
A typical HDR would have say, 5-7 different actual pictures of evaxtly the same thing, but with different apature settings. The reasons are simple. Normal imagry simply can not hold more info than it can capture. But, by combining multiple pictures, each with different exposures, you have everything you need. You have pictures with detail in the darks by over exposing it, and you have pictures with details in the highlights by underexposing it.
Start off with just your setup and then take a picture. Then up your fstop and take a picture, than up it again and take another. Then go back to your base fstop, back it down one, take a picture, back it down another, and take another picture. The result in that case would be 5 pics of differing exposure starting from underexposed all the way to overexposed. Combine them and you have all those varying degrees or whiter than whites and blacker than blacks to use as you please.
In the situation you described surf, it would not be 2 pics at 90 degrees, but 10 at 90 degrees. 5 pics up and down the apature from each angle.
But, for most purposes, you can CERTAINLY create an image based on your method that would serve a lot of purposes. Unless you REAALY need all that additional light info (and sometimes you really do) you can get away with taking only 2 pics at different angles or maybe just 6.
The important thing to remember is the purpose: To be able to get all the highlight, shadow, and midtone detail you could want.
A typical HDR would have say, 5-7 different actual pictures of evaxtly the same thing, but with different apature settings. The reasons are simple. Normal imagry simply can not hold more info than it can capture. But, by combining multiple pictures, each with different exposures, you have everything you need. You have pictures with detail in the darks by over exposing it, and you have pictures with details in the highlights by underexposing it.
Start off with just your setup and then take a picture. Then up your fstop and take a picture, than up it again and take another. Then go back to your base fstop, back it down one, take a picture, back it down another, and take another picture. The result in that case would be 5 pics of differing exposure starting from underexposed all the way to overexposed. Combine them and you have all those varying degrees or whiter than whites and blacker than blacks to use as you please.
In the situation you described surf, it would not be 2 pics at 90 degrees, but 10 at 90 degrees. 5 pics up and down the apature from each angle.
But, for most purposes, you can CERTAINLY create an image based on your method that would serve a lot of purposes. Unless you REAALY need all that additional light info (and sometimes you really do) you can get away with taking only 2 pics at different angles or maybe just 6.
The important thing to remember is the purpose: To be able to get all the highlight, shadow, and midtone detail you could want.
oneinfiniteloop
Veteran
Greg Ward (http://www.anyhere.com/) suggests taking 10 pics changing the shutter speed and leaving aperture fixed. He has a lot of good info on the subject, as well as Paul Debevec, http://www.debevec.org/
Matt Grunau
Adobe Demigod
oneinfiniteloop said:
Same thing really, differing shutter speeds would result in differing amounts of exposure. Had'nt heard that though. Downloading some info from his site now.
Good one dude.