For an interior shot, 12 EVs is usually enough, but for an outdoor shot where the sun is visible, you might need around 22 EVs to capture everything depending on the time of day and the weather. My point is this: It’s quite difficult to capture the whole dynamic range of a scene in many cases. Thus you can shoot a larger exposure range and, with a strong enough filter, capture the entire brightness of the sun. You can buy Neutral Density filters, which essentially block a certain amount of light, allowing you to shoot darker photos.
Since this is a difficult problem to solve, most folks just don’t bother at all and thus we’re left with HDRIs that do not contain the entire brightness of the sun.įlashing red area is a solid colour, indicating the brightness is clipped and therefore incorrect.īut it’s not an impossible problem. And usually the fastest any typical commercially available camera will go is 1/4000 or 1/8000 (which is still not enough). The sun is so bright that even 1/4000th of a second is too long and captures too much light. For example, any time you need to capture the sun. The challenge comes in when the range of brightness you need to capture is so high that it’s difficult to get it all in one go. This is all quite easy to do, in fact the camera does all the work of calculating the right values and capturing them in sequence, all you have to do is point and shoot. which means the dynamic range is really 12 EVs (4×3). You might think that 5 photos with 3 EVs between them would mean a dynamic range of 15 EVs (5×3), but in fact there are only 4 gaps between the 5 photos. The exposure times would be 1/4000th, 1/500th, 1/60th, 1/8th of a second and finally 1 whole second.īoth the light bulb and the darkest shadows are properly exposed
So to capture all of this you would shoot 5 photos with a 3 EV gap between each one. The filament of a light bulb might only be properly exposed (not over-bright or “blown out”) at 1/4000th of a second, and in the same view you can see the corner of the room cast in shadow, which might require an entire second of exposure before it’s bright enough to see clearly. Instead they do 1/15th because they want to make our lives difficultīut most environments have an extremely wide range of brightness. Side note: Cameras can’t do 1/16th exposures, You might start with an exposure of 1/16th of a second, then do 1/8th and then 1/4th. But it seems to be the norm for HDRI dynamic range measurements to ignore this fact and just include the range between the shutter speeds.)Įach EV means double the lighting information, so a dynamic range of 2 EVs means you captured three photos, each one doubling the last exposure time. (Side note for you techies… This is a pretty silly way to measure it in my opinion, because a single shot already encompasses a certain range of brightness (dynamic range), and depending on the camera you use this can vary between 10 and 14 EVs. So if you capture two images, one twice as bright as the other (double the exposure time), and merge them into a single image, that new image would have a dynamic range of one EV. But an exposure value (in terms of HDRIs) is a measurement of the range of exposure. Typically you’ll see something like “12 EVs” which means that when they took the photos, for each camera angle they captured multiple photos at different exposures that encompassed a 12 EV range.īut what the heck is an EV in the first place? Well it stands for Exposure Value. As you might know, exposure refers to the amount of time that the camera shutter is open, and thus the amount of light that gets captured on the sensor. Let’s begin with what is, to me, the most important aspect of any HDR image that you intend to use for lighting.ĭynamic range is an indication of the contrast in an image. Just like art, the quality of an HDRI can be a subjective thing, but I think we can all agree that there are a few fundamental attributes that define (although not exclusively) how useful or accurate an HDRI is. So without further ado, let me explain… What Makes a Good HDRI In truth, this is an unending quest, but I’ve made some fair progress over the years. I wanted to create the perfect high dynamic range environment map that would give you perfectly accurate and realistic lighting as if you had teleported your CG scene to the actual location of the photo itself. So, after I created my first crappy HDRI and discovered how challenging it could be, I decided to embark on a quest.
Vray hdri software#
If you’ve got a half-decent camera, a tripod and some software you can even make them yourself.īut just like creating art in Blender, being able to do it at all is not the same as being able to do it well.
Vray hdri how to#
FebruWhat Makes a Good HDRI and How to Use It Correctly
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