Light meter - Backlight? What exactly is it doing? at DVinfo.net

Larry Cohen · May 11th, 2011, 07:58 PM

Hi,
I have an XF300 - Sometimes when I'm shooting outside - say of horses running around - sometimes they'll run towards the sun. Or the background will change as they trot around and I'll get a LOT more sky in the background. Of course, the dark horse with the additional backlighting becomes too dark.
Sooo, I would think I would assign a button so I can quickly push an assigned button, and the camera will go into the "backlight" mode. But as I play with it, it just looks to me as though it "overexposes" the scene by about 1/2 stop. Is that what the camera is doing? Is it basically just "overexposing" the scene by about 1/2 stop? I would've 'thought' the meter mode changes and "looks" for strong backlighting and then compensates . . . but that doesn't seem to be what's happening. Unless I'm wrong?

To me as I move the camera around looking closely as I toggle backlighting ON and OFF - it just looks like the entire image picks of about 1/2 stop.
Anyone have any observations on this?
Thanks,
Larry

Robin Davies-Rollinson · May 11th, 2011, 11:36 PM

The backlight function is indeed overexposing slightly, which is what it's supposed to do. When you are in auto-exposure mode and your subject - let's say a person - is backlit - with a strong halo of light around it for example, the autoexposure will want to compensate for the brightest area and stop down the iris, so the face will go darker. The backlit feature will open up the iris to try to get a better exposure and the face will be be properly exposed, BUT other areas around the subject will appear to be overexposed. It's a trade off.
Far better to just use manual exposure and select what's important in the scene as regards exposure...

Larry Cohen · May 12th, 2011, 07:39 PM

Robin, thank you very much for your helpful reply. Just by confirming what I was finding - makes me feel like I do understand what's going on! Thank you.

Let's see . . . while I have you :) maybe can I pry some more info out of you ! Maybe you'll know this, too. I usually shoot 1280x720, because I do a lot of overcranking. Frequently I'll use 48fps or 60 fps - the results are always stunning. Oh, we use Final Cut Pro and are big in Apple!

So I use the 50mbs setting on the camera, and keep the frame rate (NOT frames per second) at 30p. Then I'll overcrank to 48 or 60 frame per second. But I'm a little confused at shooting at 30P vs. 60P. But THIS doesn't refer to frames per second. So I guess what I don't really get - is should I always default at 30p which is what I do? Or should I use the 60p setting? Again, I'm NOT talking about frames per second. My results seem to look very good - even though I don't really know what I'm doing! I kinda do! Thanks, Robin. I really appreciate your reply, to this Yankee Doodle in New Jersey!

May 11th, 2011, 07:58 PM	#1
Larry Cohen Regular Crew Join Date: Aug 2010 Location: Watchung New Jersey Posts: 50	Light meter - Backlight? What exactly is it doing? Hi, I have an XF300 - Sometimes when I'm shooting outside - say of horses running around - sometimes they'll run towards the sun. Or the background will change as they trot around and I'll get a LOT more sky in the background. Of course, the dark horse with the additional backlighting becomes too dark. Sooo, I would think I would assign a button so I can quickly push an assigned button, and the camera will go into the "backlight" mode. But as I play with it, it just looks to me as though it "overexposes" the scene by about 1/2 stop. Is that what the camera is doing? Is it basically just "overexposing" the scene by about 1/2 stop? I would've 'thought' the meter mode changes and "looks" for strong backlighting and then compensates . . . but that doesn't seem to be what's happening. Unless I'm wrong? To me as I move the camera around looking closely as I toggle backlighting ON and OFF - it just looks like the entire image picks of about 1/2 stop. Anyone have any observations on this? Thanks, Larry

May 11th, 2011, 11:36 PM	#2
Robin Davies-Rollinson Trustee Join Date: Dec 2002 Location: Gwaelod-y-garth, Cardiff, CYMRU/WALES Posts: 1,215	Re: Light meter - Backlight? What exactly is it doing? The backlight function is indeed overexposing slightly, which is what it's supposed to do. When you are in auto-exposure mode and your subject - let's say a person - is backlit - with a strong halo of light around it for example, the autoexposure will want to compensate for the brightest area and stop down the iris, so the face will go darker. The backlit feature will open up the iris to try to get a better exposure and the face will be be properly exposed, BUT other areas around the subject will appear to be overexposed. It's a trade off. Far better to just use manual exposure and select what's important in the scene as regards exposure... __________________ TV Director / Cameraman

May 12th, 2011, 07:39 PM	#3
Larry Cohen Regular Crew Join Date: Aug 2010 Location: Watchung New Jersey Posts: 50	Re: Light meter - Backlight? What exactly is it doing? Robin, thank you very much for your helpful reply. Just by confirming what I was finding - makes me feel like I do understand what's going on! Thank you. Let's see . . . while I have you :) maybe can I pry some more info out of you ! Maybe you'll know this, too. I usually shoot 1280x720, because I do a lot of overcranking. Frequently I'll use 48fps or 60 fps - the results are always stunning. Oh, we use Final Cut Pro and are big in Apple! So I use the 50mbs setting on the camera, and keep the frame rate (NOT frames per second) at 30p. Then I'll overcrank to 48 or 60 frame per second. But I'm a little confused at shooting at 30P vs. 60P. But THIS doesn't refer to frames per second. So I guess what I don't really get - is should I always default at 30p which is what I do? Or should I use the 60p setting? Again, I'm NOT talking about frames per second. My results seem to look very good - even though I don't really know what I'm doing! I kinda do! Thanks, Robin. I really appreciate your reply, to this Yankee Doodle in New Jersey!