Best way to slightly underexpose in auto-iris?

D

Danny1280

Well-known member
Hello all,

I'm actually much more comfortable getting proper exposure with tungsten lighting. I check my wave form, and get eveything in that sweet spot, no clipped highlights, etc.

Outdoors, I'm still a work in progress. For run-and-gun, I've been using auto-iris, just because I simply can't keep up with adjusting it manually when the lighting changes so quickly. When I do that, I've been getting a lot of clipped highlights. I generally prefer a slightly underexposed look. Is the best/only way to go in through the scene file (I usually use Spark) and adjust my A.Iris level? Or is there a global way to affect it, independent of scene file? Also, does anyone have any experience with what the numbers mean on the A.IRIS setting? For instance, what would be a good setting if I wanted it 1/2 stop darker. Or one stop darker? (The numbers go from -6 to +6)

Thanks in advance!
 
The A.Iris function in the AF100 provides for up to 1-stop overexposure or 1-stop underexposure. I am not near my HMC40 right now so I can't verify that offhand, but I'd bet it's the same. On the AF100 the steps are pretty evenly distributed, so A.Iris -3 would tell it to underexpose by about a half a stop, and A.Iris -6 would tell it to underexpose by about a full stop.
 
Yep the 150 works just like that. I actually push mine the other way as I find the 150 to be a bit too conservative if I have to use auto iris.
 
Thanks, Barry and Jystyn.
Interesting about Justyn's opposite results. Wondering if it's dependent upon the scene file. Like, maybe Spark is a higher exposure?
Having not played around with knee, how would you say that plays into the equation?
For instance, would leaving auto iris where it's at, but bringing the knee down one notch... would that give me a better dynamic range w/out clipping highlights, compared to taking the auto iris down?
 
We're not having opposite results... the A.Iris Level setting lets you go to 1 stop over, or 1 stop under, whichever you prefer. Your original post asked about going for underexposure, so that's what I described the settings for.
 
Sorry, Barry. I wasn't clear. I meant that Justyn and I had opposite results when using auto-iris. He needs to increase to his auto-iris to get a good exposure, and it seems I have to decrease mine. Bringing my auto-iris footage into FCP, I see clipping warnings show up. Thanks again for your help.
 
Danny... Yes you might be getting that under uncontrolled conditions... but most of my shooting lately is under lighted conditions and on a steadicam or such where I can't use manual iris. I can see what you are talking about if you are going to be shooting outsider or such.... and yep the whites will blow out quite easily, but it's a lot better than it is on my SD9 or other cheap crash cams... Those willl really blow the whites out...

I do though really like to push my exposure and Barry's advice about 105 zebras is so rock solid it's never failed me..
 
Justyn, thanks again for your response. Can you help me with a little confusion on my end about the 105 zebras? Wouldn't setting them to 105 make it more likely to risk clipping/blowing out whites? As opposed to using a lower zebra warning, like, say 80?
 
When you set your zebras at 105, you make sure that they never, ever, ever show up. If you see 105 zebras, then yes you're clipping. If you never ever see zebras at 105, you're extremely likely to not be clipping anything. And since writing that, I've now pulled back my recommendation to say that for most folks, riding the ragged edge at 105 might be a bit much, and they should consider setting their top zebras at 100.
 
Barry that might be a good conservative estimate especially for new camera owners. I've had great results from the HVX to the 150. It's so bloody hard to do this on the 7D and other DSLRs that dont have zebras and a waveform. I've just begun to be so happily reliant on them.... Thanks to you and your and have a great Holiday season!
 
Danny, I am glad you started this thread as I have been having the exact same issue..I too am using mostly "spark" scene file.

I would be curious to know how things have been working out? Did you go for the 1-stop under exposure thing while using auto-iris? I have not gotten around to trying it myself.

The one thing that worries me, is what will be the exposure result when zoomed in? While I have been experiencing the blown highlights, it has always been when zoomed way out. When I zoom in, I don't seem to have those issues near as much. And if I use auto iris and set to under expose by one stop, I am worried that the zoomed in shots will be too under exposed. Of course I am sure it doesn't help that the situations I am experiencing this are all run and gun available light (which is always less than ideal to say the least).

I guess I need to just get out there and try some more different settings. I was just curious how things were working out for you?

Regards,

G.
 
Hi G. Yes, I need to do the same. Get out there and run a bunch of informal tests. I'll let you know my results if I do.
 
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