F350/F330 Auto Iris issues at DVinfo.net

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Old October 30th, 2006, 02:48 PM   #1
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F350/F330 Auto Iris issues

I have been having issues with the way the auto iris behaves from the outset. While I can turn the response speed down on the lens and in the menus I still find the speed to be too fast, the response is also asymetric. That is to say the Iris will stop down very readily but then not open up quite so willingly.

Here's one for all you owners to try. Turn on the auto iris shoot a wide shot with a bright window or other bright object filling a large part of the image. The iris will attempt a correct exposure normaly fairly accuratly. Slowly pan off the window watching the iris. On my camera it dosn't open up until there is absolutly no trace of the bright object left, then it suddenly snaps to the new exposure.

I have demonstrated this to a Senior Sony XDCAM engineer and have been told they will look at it.

Anyone else having auto iris issues?
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Old October 30th, 2006, 02:55 PM   #2
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I had some crazy cycling the other day, after taking the camera outside for a moment. I didn't see this at all before the firmware upgrade (but then again, I wasn't touching it because it was underexposing so badly in 24p).

I was going to try to slow it down the next time I thought of it.

Now that the Cinegammas are placing whites at 100, I can use 100% zebras like I've been used to!

New firmware solved lots of stupid problems for me.
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Old October 31st, 2006, 05:04 AM   #3
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Alister, I just tried this with F350 and CAnon HD lens (not that the lens makes any difference).

When I put it into Auto-Iris mode it does the same thing you said.

Just now I stood in my living room and filled the frame with the window and it was exposed perfectly, I then slowly panned towards the inside wall of the living room, when the window was virtually 98% out of frame (just a tiny vertical line down the edge of the frame) the iris suddenly zips the exposure right up to bring the darker inside wall of the living room up to the right exposure.

Thinking back to my stills photographic days, this is about as far from "Average Area Metering" as you could get. I could not say for sure if this is an issue, or whether is is just supposed to work like this. The auto-iris tracks things perfectly outdoors; well as perfect as I've seen any auto-iris system work anyway.

For the issue that you are experiencing, that I did too after testing, it's almost like it needs a transition into the new iris setting, rather than just banging straight up/down into the new iris reading.

I would never have noticed this as I always use in manual; though there are instances that Auto would be required.

Anyway, you are not alone.
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Old October 31st, 2006, 07:52 AM   #4
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Well Alister,

I just tried it and mine tracked fairly linear throughout the pan. On the full window, it was F11. By the time I had half the window in the shot, the lens had opened to F5.6 and when totally on the wall, it was wide open.

Camera gain is at -3 and lighting is early morning full sun. I watched the auto iris as I did the pan several times and it didn't seem to hang open and then close down suddenly. I'm using the Fuji 18x5.5. I haven't modified any of the auto iris settings (because I don't use it much).

-gb-
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Old October 31st, 2006, 08:54 AM   #5
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Thanks Greg and Nigel.

So could this be a Canon only problem??

I first encountered this effect when tracking aircraft across a cloudy sky, the bright clouds would hold off the iris until out of frame. It's certainly a strange behaviour.

I normally use manual iris, but there are some shots where auto iris works better, but I do find the F350 iris response to be too fast for me.
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Old October 31st, 2006, 09:22 AM   #6
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Funny, in hindsight, I think it could be the lens. The one I'm using right now is the Canon KH20x6.4 HD lens. I wider lens might not have these issues. I suppose it depends on how Sony calibrated the auto-iris system and with what lens/lenses.

Trying the F350 with above lens outside has more accuracy, but it still tends to wait until the last minute before adjusting itself.

If I do a slow tilt from the bright sky down into my garden, the sky is virtually disappearing out of the top of the frame before the iris kicks in and brightens up the garden. If you were recording this way it would look really amateurish as it is obvious the auto-iris is switched in.

The cam I have also has the very latest firmware update with the catch memory function. The new firmware has also fixed the auto-iris problem i.e. before if you had cam in 25P mode with shutter turned on at 50, the auto iris would not compensate for shutter been turned on and underexpose by 1 to 2 f-stops. Now it is fixed and it compensates for this exactly; nice!

Let us know is it does it with wider lenses if you get your hands on one Alister.

Cache record time function in menu has:

0-2 sec
2-4 sec
4-6 sec
6-8 sec
8-10 sec
10-12 sec

Haven't tried them yet and not sure what the above figures mean exactly.
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Old October 31st, 2006, 09:39 AM   #7
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Hi, does the camera have an auto iris function? Sorry just a bit of an in joke, I was with another cameraman last week who claimed jokingly he didn't know what that switch on the lens was for.
I found in a theatre with the first version of the firmware that there was some hunting of the auto iris, only solution was to go manual

Andy
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Old October 31st, 2006, 10:08 AM   #8
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Quote:
Originally Posted by Andy Walton
Hi, does the camera have an auto iris function?
I haven't met anyone who uses the auto iris. Unless you are in a completely controlled situation (or just lucky with lighting), auto iris will open and close for any irregularities in lighting. Any bright area or large dark area will give you an unnatural exposures elsewhere in the frame.
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Old October 31st, 2006, 10:13 AM   #9
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Matthew, Alister and I are well aware of this. Manual is the way to go, ALWAYS, I personally never use auto. But I believe Alister needs the Auto Iris function on the odd rare occasion due to the kind of stuff he shoots, very uncontrollable lighting conditions etc.

But what we are trying to establish here is whether it is the camera at fault or the Canon 20x lens. I know Auto should not be used and rarely is by pros, but this doesn't change the fact that this rarely used feature appears to be slightly flawed in its operation.
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Old October 31st, 2006, 10:19 AM   #10
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Quote:
Originally Posted by Nigel Cooper
Cache record time function in menu has:

0-2 sec
2-4 sec
4-6 sec
6-8 sec
8-10 sec
10-12 sec

Haven't tried them yet and not sure what the above figures mean exactly.
And it's my understanding that you normally won't see any cache action on the 0-2 setting. The 2 second variation on each setting is likely due to interaction with the shock buffer which uses the same memory IIRC. So a smooth ride might get you the higher number, while bumps and shakes might result in the lower end figure. I'm only speculating, not claiming the gospel truth on this.

You also have to turn cache record to ON which is the menu setting above the time window.

-gb-
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Old October 31st, 2006, 10:42 AM   #11
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Quote:
Originally Posted by Nigel Cooper
But what we are trying to establish here is whether it is the camera at fault or the Canon 20x lens. I know Auto should not be used and rarely is by pros, but this doesn't change the fact that this rarely used feature appears to be slightly flawed in its operation.
I have the Fujinon 16x4.6 on my 350 and it behaves the same.

My point above is that I've never used any auto iris function that didn't have this "flaw" you are speaking of. It's not really a flaw, it's (as I'm sure you're aware) just how any auto iris behaves.

If Alister is using the auto iris in "very uncontrollable lighting conditions etc." the problems will be even more exaggerated, as you know.
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Old October 31st, 2006, 10:49 AM   #12
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That's not true - I shoot a lot at airshows and it's impossible to manually expose when you following aircraft at 300 mph acros 270 degrees of sky in variable lighting conditions. Every other camera I've filmed with from a BVW 400 to an HDW 750 has the ability to slow the iris response down and it works very well.

The 350 simply doesn't do it correctly
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Old October 31st, 2006, 11:16 AM   #13
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Apparently Sony wants you to purchase the RM-B150/B750 Remote Control Unit. 8-(

According to page 65 of the second version of the F330/F350 user manual the remote control can be used to adjust iris sensitivity.

"Pay me now or pay me later."

Carroll Lam
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Old October 31st, 2006, 12:44 PM   #14
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The iris sensitivity can be adjusted - it just doesn't work
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Old October 31st, 2006, 02:26 PM   #15
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The iris should not be behaving the way it is. According to the manual you can choose between center metering or average exposure. The iris should give a useable exposure at all times, it may not be perfect, it may not compensate fo highlights or lowlights, but it should not allow a situation where all but 1 or 2% of the entire frame is totaly dark, except for a sliver of a highlight at the edge of the frame.

As Steve says it is impossible to pull focus on a fast moving object, using the zoom and track the exposure while the sun is going in and out behind clouds while working at the long end of a 40x lens. I have this very problem when shooting motor racing and aircraft. I also use auto iris when I am jumping in and out of cars and vans in 60 mph winds with driving rain, lightning and a deadly tornado bearing down on me. Belive me you want as little to worry about as possible. The auto Iris on my Digibeta and DVCAM camcorders worked fine, the F350, even with the latest firmware just dosn't behave as I would expect.
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