HDRI: hdr files vs jpg files

Scavenger

I'm looking at some free HDRI's I'm finding online.

They come in various versions..big sizes, small sizes.. jpgs and hdr's....

Which should be used?

the jpgs are physically bigger pictures, and look better as backgrounds, but don't the .hdr's have more info?

Fishtales

The HDRI you have highlighted is light only, the one you want for background and light is the 2048 one, which is quite low for an HDRI. The .jpg ones are for backgrounds only there will be very little light coming from them to use as an HDRI in the dome and you would need extra lights added to compensate e.g. put a distant light for the sun and move it to the sun position.

Scavenger

Well, the one i highlighted is just a happenstance of fate...

The 2048 is the big hdr.

the big jpg is the full.jpg which is 5952 × 2976 pixels

In iray's Enviroment, tab, I only see one place for a map...is it one or another, but not both?

fastbike1

Only one map. Lots of free hdri's available, but relatively few of them have enough range to provide good lighting. Fewer still of .jpg that actually have good lighting.

Bottom line: just because it says HDRI doesn't qualify it as useful for iray lighting use.

Tobor

While there are 32-bit versions of JPEG files (usually with the .JXR) extension, there's no "HDR" in an standard 8-bit JPEG image, so skip these unless you just want the background image. As noted above, while these *will* provide light, it will be diffuse and rather flat.  You need the range -- the "R" in "HDR" that 32-bits provide.

Files with an extension of .HDR are likely -- but not guaranteed -- to be 32-bit, which are suitable for both whatever image is contained in them (you can't have light emitted without something showing in the picture), as well as the lighting effects.

There is only one place to plug in an environment map. You use either the JPEG or HDR version, whichever suits your application. A 2K HDR is probably meant to only provide a specific light, rather than a detailed scene. Free HDRi's are often limited in this way, so if you want a hi-rez HDRi version, you might have to pay for it. That said, there are still plenty of really nice 4K-8K HDRi's out there that are free, and don't have commercial license restrictions.

mjc1016

Tobor said:

 

There is only one place to plug in an environment map. You use either the JPEG or HDR version, whichever suits your application. A 2K HDR is probably meant to only provide a specific light, rather than a detailed scene. Free HDRi's are often limited in this way, so if you want a hi-rez HDRi version, you might have to pay for it. That said, there are still plenty of really nice 4K-8K HDRi's out there that are free, and don't have commercial license restrictions.

Link in my sig...I highly recommend the HDRIHaven images.  Greg Zaal has several very large (pixel size), high range freebies and all of his images have at least a 1-2K 'light only' free version.  Plus, the 'full size' versions of everything else are fairly inexpensive...some up to 16K (a 16k image used for a backdrop is very detailed...). 

There are several other sites that have good mid to large images that are suitable for use as both backgrounds and lighting.  The key factor, for lighting, is a very wide range image.  The key for background use is resolution.  Combining both those elements in a single image will also mean a large file size.  So keep that in mind, too...a small file size for an 8K image means it probably isn't really all that good...especially for use as a background.

throttlekitty

HDRI's have multiple exposure photos inside them, so it's much easier to control the lighting with those.

fastbike1

I will second the recommendation for Greg Zaal's images. Well worth the modest fee, both for lighting and background.