Automatic & Manual Gain
 

Dear Friends

I know that in order to have full manual control of my exposure I need to manually control my shutter speed, iris and gain. But is there a way of 'locking' the automatic gain in the same way that the automatic iris can be locked?

Failing that, how do you good folks set your gain? Do you have rule of thumbs for certain enviroments, or do you just use what feels 'right' at the time?

Thanking you for your trouble,

Saxon

Pressing the gain button will put it on manual. However you will then need to program the 3 position switch to the desired levels (or accept whatever the defaults are, can't remember).

It depends on what I'm shooting as to what I set the switch. For work in relatively bright places I set it to 0-3-6. For dark stage shows I might use 3-6-12. For stage shows with a lot of variation in levels I might choose 0-3-9. In really dark places you might want 12-15-18.

You need to gain a little experience with what to expect in order to refine the settings for a given situation. But I really wish they had given us a dial where we could just pick any level we want. And that would also allow a smooth transition instead of discreet "bumps" with the switch.

I leave my gain on manual and then tend to have the three different positions on the gain switch set to something along the lines of 0dBs 6dBs and 9dBs.. although i havent used gain in so long im not even sure if those numbers are accurate.

Joe

The FX1 comes with the factory default levels at 0, 9 and 18. Pages 28 and 29 of the FX1 US manual have all the details.

Page 52 discusses how to change the values in the 3-position switch.

You can also set an automatic gain limit through the use of picture profiles (pp 34-35).

Automatic & Manual Gain
 

Many thanks for these answers chaps.

In actual fact, I have set my Gain levels (for me it's 0-9-12), but was uncertain how folk decide which gain settings to use in different circumstances. Boyd's figures show that there's a fair amount of scope for me to experiment.

I was wondering if I could somehow lock the AUTOMATIC gain setting, just as I sometimes lock the automatic iris.

As this is my first thread, I'd also like to say how incredibly helpful this forum has been in offering so many viewpoints on so many topics.

Best wishes,

Saxon

Hi Saxon,

I guess actually you are asking is if the gain can act like the iris does when you leave auto iris. Using the camera to auto set the gain, (say at 6.8 db or some arbitrary figure) then leaving it locked at this setting.

I'm afraid it can't.

When you switch out of auto gain it will adjust to whatever the gain switch position is in.

Why? Because the gain switch is set in one of three positions.

The Iris wheel however turns with (on a proper lens) a stepless range of settings. That's why it acts differently. Also the camera should be used on a certain gain/shutter setting, then the iris is used for fine control.

No-one would leave the iris on a camera and adjust gain to correct their exposure. (I'm not suggesting that's how you do it of course!) If you needed a certain f-stop you should set the iris, then the gain to an acceptable level, also adjusting NDs and the shutter speed for correct exposure.

It's how things are done on full size kit, and it's been handed down to the Z1.

Personally I quickly switch from auto gain to a manual gain setting with the iris and shutter set and locked (I always have the shutter on 50 for normal shooting - I'm PAL here too).

If there's a huge change in exposure I'll know the gain setting needs adjusting. Switch back and forth until you're in a ballpark area. However the LCD on the Z1 is just so incredible, and works in any light, that manual exposure is really easy. Also 12dB of gain still looks really clean.

So I use 6dB and 9dB, or 9dB and 12dB.

Don't forget you can try a test recording, with autogain on. The review the recording, hits the datacode button twice and see what settings the camera decided to use for it's gain. It only shows 3-6-9-12 etc, not sub divisions however.

Sorry for the waffle, hope this helps.
Duncan.

I think I understand what your question is all about. The manual buttons on the FX1 are not really straight forward. Pressing the set to manual( middle switch position), then pressing iris, locks at the current setting( but does leave ALL the others in automatic), continuing to press gain redirects the auto setting to the setup of the switch( ie it doesn't lock at the current setting which I think is what you would like?). IF you want to HOLD all the setting you can set HOLD with the selector switch. This will hold all the settings. There are a lot of control settings in the Picture Preset menus that you may want to explore such as sharpness, AE shift, gain limit, iris limit etc.

Ron Evans

Oops forgot to ask if it's the Z1 or the FX1 we are talking about here....

Either or. They both work the same that way.

I thought the FX1 and Z1 were similar too, but some posts above had me a little baffled until I read them again.

The Z1 is totally logical and simple to use, I can't see where the issue is here.

Firstly, I never use the hold or autolock function - ever. I wouldn't trust any camera to auto everything. And I always use the camera based on full manual anyway.

I say 'based on full manual' as I'll switch to auto iris to check I'm not miles from where the camera thinks I should be, then adjust as I see fit. Then when required, I'll switch to auto white to check I'm correct on whites. I'll do this when I'm repositioning or reframing, not during a take.

Obviously I'll only use auto iris and white when I'm framed on a proper reference image eg. neutral colour and neutral lighting.

If, once I switch back to manual iris and the readout says I'm almost opened up fully I'll drop in some more gain for example, and repeat the auto routine.

So:

Iris control on the front silver wheel.
Gain on the 3-way switch , no camera has a variable smooth gain control (edit) - AFAIK
Shutter on the back wheel.
ND slider on the side.

That's 4 controls and 4 buttons

Then there's the well placed white balance buttons and most importantly white shift, which I have assigned onto Buttons 1 & 2.

All of these functions (except ND) can be adjusted instantly and whilst filming on my DV Rig Pro or a tripod. It's as easy as a full size camera (with shutter at the front of the camera) Even easier, when you consider the screen is so good you can get great colour with the white shift as well.

P.S. I use a Picture profile with boosted chroma, some softening, black stretch and AE at -1 stop.

Regards, Duncan.

Automatic
 

I say 'based on full manual' as I'll switch to auto iris to check I'm not miles from where the camera thinks I should be, then adjust as I see fit.


Sorry, was trying to bookmark and sent .. .

Thank you Duncan, and everyone, for your replies.

With your viewpoints and more experimentation at the weekend, I'm sure that I'll get more confident with the Gain!

Best wishes,

Saxon

Good luck this weekend.

I'm filming a huge wedding all day and night Saturday, a big commercial shoot on Sunday (Full Jib/Hothead/Track - the works).

Then my birthday bash Sunday night. :-0

I'm already knackered so who knows what I'll be like for Mondays edit !?

Duncan.