Gear Talk > Technical Support

Setting fixed aperture with auto iris lens

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emag:
I use Av mode 99.99% of the time and have since my first 'decent' camera, a Nikon F2 in 1974 and still do today with a 60D and 40D.  When I couple a camera to my telescopes I shoot manual for astro and Av for daylight work.  Recently I've encountered a situation that has me a trifle stumped - given time I might find a solution but I suspect there is a simple solution and I needn't reinvent the wheel.  With an auto iris lens I want to set the opening fixed for timelapse.  Pressing the stopdown preview, then the lens release and turning the lens ever so slightly, I can keep the iris fixed and take a shot.  BUT, I get an ERR01 (lens communication) message after the shot.  A half shutter press clears the error message and I can then take another shot (after releasing the half shutter press - i.e., it take two shutter presses).  This won't work for timelapse.  Anyone know a workaround?  I have ML but have not fully explored its capabilities, perhaps the solution is there.  Maybe it's in the manual, in which case I deserve a slap on the back of the head and a 'RTFM'.

lol:
Am I missing something here, why can't you leave the lens connected normally and use Av mode?

If for some reason you can't do that, you were half way there will the partial twist method. Set desired aperture, press and hold DoF preview, and twist off the lens which will remain at the set aperture. Leave the partially twisted lens in place. The camera wont know its there and can't change the aperture then.

emag:
Yes, I could use Av mode, but I am trying to have the lens remain at the desired aperture setting rather than stopping down for each shot, it reduces the possibility of flickering due to the iris not closing to -exactly- the same position each time. You've given me a thought - I may need to twist the lens a bit more or remove and then partially remount it.  Thanks.

paul13walnut5:
Apart from anything else, even if the aperture did stop down exactly the same each time, it's a hell of a lot wear.
300 stop downs for 10s of timelapse?  Not good.

It does sound like you haven't twisted the lens enough, about a third should be enough to totally disengage the comms pins but keep the lens secure.

I also would recommend looking into ND faders.  I'm not a fan generally, but this is one situation where they can be good, shoot with the lens wide open, and control the exposure with the ND fader.

As your timelapse will probably be resized to 1920x1080 at best the loss of sharpness shooting wide open isn't that much of an issue.  And theres no stop down!

ND faders dont work well on UWAs or teles above say 100mm equiv, but if you are using a typical walkaround kit zoom then they'll be fine.  Just be sure to check images on playback before you set off your timer.. live view sometimes doesn't entirely reflect whats on the card with uncoupled / manual lenses.

mws:
What about a older manual lens with an adapter? There are lots of great older lenses on ebay for not allot of money.

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