EX1 AUTO Iris/gain LOGIC seems illogical at DVinfo.net

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Old July 27th, 2008, 10:52 PM   #1
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EX1 AUTO Iris/gain LOGIC seems illogical

Got 2 EX1s last week and kicked the tires at a wedding last Sat. At the reception, it's looking a bit dim, I click my iris to manual and open it up all the way. But my assistant, in the exact same situation leaves the iris in auto. My assistant's EX1 in auto, instead of opening the iris all the way to allow more light, increases gain (in AGC mode). My video looks quite clean with the iris open - my assistants video is noticeably more grainy.

It seems illogical to me that the camera would opt to add gain first, before opening the iris all the way. Is this stupid logic or is a grainy look something Sony is assuming us EX1 owners like?

What I would really expect/like to happen is this... IRIS OPENS FULLY, THEN, AND ONLY THEN, AGC TAKES OVER. I'm not a big fan of grain but I'll tolerate what I see up to 6db on the EX1. Is there a menu setting that can require the EX1 to behave this way?
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Old July 28th, 2008, 12:43 AM   #2
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Just go into the menu options and go into the TLCS menu turn off auto gain or adjust your max gain there.
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Old July 28th, 2008, 07:53 AM   #3
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The auto Iris control in the TLCS is probably not going to allow it to open up all the way either.
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Old July 28th, 2008, 08:33 AM   #4
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Yeah, in another thread I wrote about some aspect of TLCS being very limited (like the max. auto shutter speed being just 1/200th); I'm afraid the Iris can only open up at F2.8 max.

While itself being a very clever idea basically, the TLCS is designed to not use the various EX1's settings at their extreme values... Why? Don't ask me :(

One thing you should certainly do (if using auto at all), is limit gain to some 6 dB when in auto, though.
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Old July 28th, 2008, 09:32 AM   #5
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The iris will open up to f1.9 after the gain limit has been reached. Just set a lower gain limit if you want to go to f1.9 sooner, or use the manual switch to add gain if needed.

The max auto shutter speed is 1/250 in 60i on my cam.

I'm really very happy with the way the TLCS works, in all conditions and especially low light. You just have to set the parameters for the look you want.

I have them set like this:

f2.8
f5.6
1/250
+9 db

But if it can't stay within the ranges above, it will override them at either end to insure correct exposure.
Be sure to turn Full Auto OFF, but enable AGC, enable Auto Shutter, enable auto Iris.

TLCS is a very functional feature, one of the few lacking on my otherwise excellent XH-A1.
Unfortunately, my EX1 includes a few non-functional ones as well, like the abysmal ATW and useless Auto Knee.
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Old July 28th, 2008, 11:01 AM   #6
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Tom, we have discussed the thing before and you're right - there is a logic to it (also, it's 1/250 and not 1/200 indeed). Did you check though the Iris will open up to 1.9 when the shutter speed/gain limits have been achieved?
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Last edited by Piotr Wozniacki; July 28th, 2008 at 12:41 PM.
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Old July 28th, 2008, 11:21 AM   #7
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Originally Posted by Piotr Wozniacki View Post
Did you check though the Iris will open up to 1.9 when the shutter speed/gain limits have been achieved?
It absolutely will open to 1.9 when the limits have been achieved.
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Old July 28th, 2008, 11:42 AM   #8
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But if it can't stay within the ranges above, it will override them at either end to insure correct exposure.
An unrelated side benefit to using Auto Shutter is that it seems to have intermediate or variable shutter speeds inbetween the discrete shutter speeds. It's a shame you have to use TLCS to get them.

You can easily test this by putting the gain and iris in manual, then toggle between auto shutter and fixed shutter speeds while looking at the histogram.

It would have been nice to have the actual shutter speed and gain displayed on the LCD when using these features in Auto.
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Old July 28th, 2008, 01:29 PM   #9
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It would have been nice to have the actual shutter speed and gain displayed on the LCD when using these features in Auto.
Absolutely; with my old V1E, used in run & gun style with no time for re-adjustments while shooting, it was so reassuring to have it at the fixed 1/25 or 1/50th shutter, and watch the iris open all the way up to F1.6, followed - if the lighting conditions required - by the gain raising slowly up the the limit set at some 6 or 9dB maximum (it would always do it in exactly this order). Or - when there was more light - to see gain being reduced to zero, and only then iris closing (but never beyond the F5.6 value set in the menu, in order to avoid diffraction softening). And all those values displayed in real time in your LCD/EVF.

And should those limits be too prohibitive in a given lighting situation, you would be so notified and engage the ND filters accordingly. Sounds like the amateurish, auto mode - but with all those values working logically and being actually displayed for your information, it really worked when needed.

Add to it its perfect AWB, and it becomes really strange Sony dropped this capabilities on the EX1...
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Old July 28th, 2008, 02:08 PM   #10
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Originally Posted by Tom Roper View Post
It absolutely will open to 1.9 when the limits have been achieved.
I understand how the camera works but my point is that it seems dumb. Iris should open fully, then and only then should AGC kick in. I'll be redundant: Gain should only be added after IRIS limit has been achieved.

It's puzzling to me how some are satisfied with how it works now? Compare video with iris NOT all the way open and 9db gain for instance. It's always more grainy than: iris fully open and 3db gain. Both videos may have equivalent brightness but the video shot with the iris open will have less grain. Mr Magoo could see the difference! ...and he drives his car on a roller coaster!
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Old July 28th, 2008, 02:31 PM   #11
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In some instances you may want a greater depth of field that that obtained with the wide open iris!

geoff
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Old July 28th, 2008, 03:21 PM   #12
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Originally Posted by Geoff Addis View Post
In some instances you may want a greater depth of field that that obtained with the wide open iris!

geoff
In such cases you don't use auto anything!
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Old July 28th, 2008, 03:57 PM   #13
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It seems to me that the only real solution to this would be configurable preferences - the ability to assign both limits and preferences, such as:

First, add up to 3 dB gain
Second open aperature as much as needed
Last, increase gain as needed

Or, there is always the option of shooting fully manual. Sometimes, some situations, the auto settings can be pretty important. It would just be nice if we could all dictate their logic and predetermine the order of things.
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Old July 29th, 2008, 08:22 AM   #14
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It actually should have been obvious to Sony, that all they had to do was add in to the iris points 2.8,4.0,5.6 one more....1.9.

It could be the consequence of one person in a back room coding the firmware who's not a videographer.

The same person who decided we only needed a few manual shutter speeds...


Upon self examination, it honestly reminds me of what I did when I was programming PLC's and embedded micro-controllers. The company I contracted for hated some of the restrictions I put into the code when I thought I knew more about what they did than they did. 10 years later, I took over running the company and another in Canada, and first order of business was to undo it all.
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Old July 29th, 2008, 09:02 AM   #15
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Originally Posted by Geoff Addis View Post
In some instances you may want a greater depth of field that that obtained with the wide open iris!

geoff
Just a quick curmudgeonly correction - it's actually less depth of field that's achieved by opening the iris.

Depth of field refers to the depth of what is in focus in your scene. Greater depth of field means that more of scene is in focus, and this is achieved by closing down the iris.
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