Why doesn't the iris go to "open" when I know scene is dark?

M

makeall6

Member
If there is one item I cannot understand about this great camera is auto iris. I shoot a lot of night football games. It is run and gun so I use auto iris. But even though I know the scene is dark, the iris will not go to the "open" setting. For decades I have been using a "broadcast" camera with a high dollar Fuji lens. If a particular scene was dark, that iris would open all the way and I would think about adding gain. But the 200 does not do that. I shot a game last night and had the same problem. Thoughts? I love the camera but this issue is still bothering me.

Thanks.
Tom
 
I don't own the camera, but perhaps the issue is related to the variable f/stop the camera has, where as you zoom, the widest f/stop changes?
 
This happens to me too! Auto iris doesn't seem too work correct. Example, as I'm filming in a low lite room, it is evident by using auto Iris, that the image is way to dark, the waveform monitor confirms this, by stopping at say 55 maybe 60 IRE setting on white walls. Personally I don't understand this & therefore cannot use auto Iris for anything. My biggest obstacle right now is trying to figure out why the DVX200 looks so green when filming indoors ? I'm getting ready to post on this issue as I know the camera & it's menu structure very well, but I cannot seem to overcome this greenish look (Tint) no matter what steps & what adjustments I make, there is still a greenish look to the over all image, some indoor shoots are worse then others.
 
sbossick said:
This happens to me too! Auto iris doesn't seem too work correct. Example, as I'm filming in a low lite room, it is evident by using auto Iris, that the image is way to dark, the waveform monitor confirms this, by stopping at say 55 maybe 60 IRE setting on white walls. Personally I don't understand this & therefore cannot use auto Iris for anything. My biggest obstacle right now is trying to figure out why the DVX200 looks so green when filming indoors ? I'm getting ready to post on this issue as I know the camera & it's menu structure very well, but I cannot seem to overcome this greenish look (Tint) no matter what steps & what adjustments I make, there is still a greenish look to the over all image, some indoor shoots are worse then others.
Click to expand...

I've seen several clips that are greenish as well... Have you found any solution to this and the auto-iris problem?
 
Could it be because you're zooming in and the aperture ramps from ƒ/2.8-4.5. So you expose for 2.8 but then zoom in and now the image is a stop-and-a-third under?

The aperture is 2.8 at 12.8m and when you zoom in the maximum aperture decreases until you hit 84.6m where the aperture max rests at 4.5. In other words, maybe the only way to achieve OPEN is when the lens is at 12.8m with aperture at 2.8? I'm not near my camera so I can't verify that it doesn't say OPEN when zoomed in past 84.6m and referring to the aperture being fully open at 4.5 at that point in the focal range. It probably does...especially if you hit 4.5 and keep racking the iris ring it'll remind you that's all it has left by displaying OPEN briefly. That seems right to me. Can't confirm it myself until I get back home.

Anyway, don't shoot with Auto Iris. Night football games at 4.5 are not initially pleasant. I remember shooting high school football games with a cheap Canon 75-300mm 5.6 lens and pushing Kodak T-Max 400 up to ISO 3200. You'll have to increase your gain by a lot to achieve proper exposure and appropriate shutter speed.
 
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My observation is that it doesn't register as "open" until almost a last resort. In other words, the shutter is as slow as can be allowed per given gain AND the light is still too low AND the lens is as wide as possible AND the exposure is in auto. Zoom just a little and the "OPEN" goes away and it registers the f stop. Now there may be other circumstances or zoom settings that it goes to "open" but this is pretty much what I have observed to be it's consistent behavior (for me). Also, one would think that 2.8 would = open, but not always the case unless the light drops well below what it thinks is adequate for 2.8. Kinda weird operating logic, and it may not be a defect. I've been getting in the habit of setting the aperture to 4.5 and pretty much leaving it there (light permitting & circumstances allowing me to get away with it) to avoid ramping without the shutter speed going ape $h1t. In low light, well, you either have to be pretty good - have a strategy planned out -or be resigned to getting what you get. Low light isn't this things strong point. BUT if you can plan the shot you can get away with quite a lot - you're just having to work harder at it - but the "bottom threshold" for me is decent stadium light or good street lighting. Get below that and I'm reaching for my Canon XA30 (which is a really kick-ass low light camera). But hey... if this stuff was easy, anyone would do it! :2vrolijk_08: Oh... one last observation... the lower the light, the more sensitive the DVX seems to be to correct white balance. Be off just a bit (or careless) and you can end up with some really bizarre color hues.
 
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