December 22, 2014, 06:11:32 PM

Author Topic: Strange overspec metering results with Canon 5D Mark III  (Read 5094 times)

Teemu76

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Re: Strange overspec metering results with Canon 5D Mark III
« Reply #15 on: October 01, 2013, 07:32:38 PM »
However, with a heavy ND filter (say, the 9/10-stop 'black glass') there is too little light coming in to the lens for the metering system to correctly meter. You're better off metering w/out the ND filter and adjusting X stops for the ND and then putting it on or just taking educated guesses and then adjusting based off the histogram on the back of the camera.

thought kind of complicated for him when doing timelapse. ;)

but my question still stands if the ND filter filters out frequencys and that might fool the metering too?
Not only that, but the colors of the light change as the sun goes down, so different frequencies would filter differently, its a possibility.
 
In any event, after sundown with a 10 stop ND filter is going to be a big problem, the camera metering might be totalally unreliable.

Proportion of the red decreases and proportion of the blue increases towards end of the series. Filter itself should be quite neutral. I have B+W 6 stop filter which lets too much red through.

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Re: Strange overspec metering results with Canon 5D Mark III
« Reply #15 on: October 01, 2013, 07:32:38 PM »

Drizzt321

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Re: Strange overspec metering results with Canon 5D Mark III
« Reply #16 on: October 01, 2013, 07:37:23 PM »
However, with a heavy ND filter (say, the 9/10-stop 'black glass') there is too little light coming in to the lens for the metering system to correctly meter. You're better off metering w/out the ND filter and adjusting X stops for the ND and then putting it on or just taking educated guesses and then adjusting based off the histogram on the back of the camera.

thought kind of complicated for him when doing timelapse. ;)

but my question still stands if the ND filter filters out frequencys and that might fool the metering too?
Not only that, but the colors of the light change as the sun goes down, so different frequencies would filter differently, its a possibility.
 
In any event, after sundown with a 10 stop ND filter is going to be a big problem, the camera metering might be totalally unreliable.

Proportion of the red decreases and proportion of the blue increases towards end of the series. Filter itself should be quite neutral. I have B+W 6 stop filter which lets too much red through.

I'd think that makes sense, once the sun is truly set and you're well into dusk the sky goes more blue and the sun isn't around to add the red back in via reflections. Think of walking through the middle of sky scrapers towards the evening. Even though the sun is still technically up, you tend to get very cool (towards blue) tones when not in direct sunlight.
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Teemu76

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Re: Strange overspec metering results with Canon 5D Mark III
« Reply #17 on: October 01, 2013, 07:45:00 PM »
However, with a heavy ND filter (say, the 9/10-stop 'black glass') there is too little light coming in to the lens for the metering system to correctly meter. You're better off metering w/out the ND filter and adjusting X stops for the ND and then putting it on or just taking educated guesses and then adjusting based off the histogram on the back of the camera.

thought kind of complicated for him when doing timelapse. ;)


Very :) I am spending all of my spare time to code metadata editor to be used with Lightroom. Then I can use aperture priority and auto iso of manual mode without flickering. Atleast i hope so.

Busted Knuckles

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Re: Strange overspec metering results with Canon 5D Mark III
« Reply #18 on: October 01, 2013, 10:36:20 PM »
Did you set the Auto ISO limit at 4000?  I didn't see anyone ask this question.

neuroanatomist

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Re: Strange overspec metering results with Canon 5D Mark III
« Reply #19 on: October 01, 2013, 10:49:44 PM »
Did you set the Auto ISO limit at 4000?  I didn't see anyone ask this question.

Someone did ask, but I don't think that's the issue - the min/max for the ISO range is set in whole-stop increments, ISO 3200 or 6400, but 'tweener' stops can't be set.
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duydaniel

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Re: Strange overspec metering results with Canon 5D Mark III
« Reply #20 on: October 02, 2013, 12:04:28 AM »
Did you set the Auto ISO limit at 4000?  I didn't see anyone ask this question.

Someone did ask, but I don't think that's the issue - the min/max for the ISO range is set in whole-stop increments, ISO 3200 or 6400, but 'tweener' stops can't be set.

on 5D3 the auto iso can be in between "full stop" iso
such as iso 3200-4000-5000-6400 etc

neuroanatomist

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Re: Strange overspec metering results with Canon 5D Mark III
« Reply #21 on: October 02, 2013, 09:30:27 AM »
Did you set the Auto ISO limit at 4000?  I didn't see anyone ask this question.

Someone did ask, but I don't think that's the issue - the min/max for the ISO range is set in whole-stop increments, ISO 3200 or 6400, but 'tweener' stops can't be set.

on 5D3 the auto iso can be in between "full stop" iso
such as iso 3200-4000-5000-6400 etc

Of course it can (in fact, with Auto ISO there's no way to not have it use the tweener ISOs, even if you want that).  But my point is that the maximum ISO limit cannot be set to an in between value, only to full stop increments.  The issue that the OP mentioned was the camera selecting ISO 4000 as the exposure got darker and darker, and since that's a tweener value, a setting that limits the ISO to a max 4000 isn't a viable explanation, since it's not possible to set such a limit, only ISO 3200 or 6400 could be set.
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Re: Strange overspec metering results with Canon 5D Mark III
« Reply #21 on: October 02, 2013, 09:30:27 AM »

Teemu76

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Re: Strange overspec metering results with Canon 5D Mark III
« Reply #22 on: October 02, 2013, 11:24:18 AM »
Did you set the Auto ISO limit at 4000?  I didn't see anyone ask this question.

Maximum auto ISO limit was 12800. I think I managed to prove that whole point about camera not selecting ISO values above was limit in metering system. In this case exposure value was EV -3 (1.6s, F2.8, ISO 4000). With F4 lens that limit was EV -2 and with F1.4 lens limit was EV -5. So it seemed that limit for camera metering was EV -6 with theoretical F1.0 lens and less with dimmer lenses. Each stop of lens brightness drops maximum meterable exposuer by one stop.

Reference for calculation of exposure value:
http://en.wikipedia.org/wiki/Exposure_value

duydaniel

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Re: Strange overspec metering results with Canon 5D Mark III
« Reply #23 on: October 02, 2013, 02:17:41 PM »
max auto iso is 25k on 5d3
you need to set it

Did you set the Auto ISO limit at 4000?  I didn't see anyone ask this question.

Maximum auto ISO limit was 12800. I think I managed to prove that whole point about camera not selecting ISO values above was limit in metering system. In this case exposure value was EV -3 (1.6s, F2.8, ISO 4000). With F4 lens that limit was EV -2 and with F1.4 lens limit was EV -5. So it seemed that limit for camera metering was EV -6 with theoretical F1.0 lens and less with dimmer lenses. Each stop of lens brightness drops maximum meterable exposuer by one stop.

Reference for calculation of exposure value:
http://en.wikipedia.org/wiki/Exposure_value

Teemu76

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Re: Strange overspec metering results with Canon 5D Mark III
« Reply #24 on: October 02, 2013, 03:06:23 PM »
max auto iso is 25k on 5d3
you need to set it

Did you set the Auto ISO limit at 4000?  I didn't see anyone ask this question.

Maximum auto ISO limit was 12800. I think I managed to prove that whole point about camera not selecting ISO values above was limit in metering system. In this case exposure value was EV -3 (1.6s, F2.8, ISO 4000). With F4 lens that limit was EV -2 and with F1.4 lens limit was EV -5. So it seemed that limit for camera metering was EV -6 with theoretical F1.0 lens and less with dimmer lenses. Each stop of lens brightness drops maximum meterable exposuer by one stop.

Reference for calculation of exposure value:
http://en.wikipedia.org/wiki/Exposure_value

Maximum value for auto ISO upper limit is 25600 but I used 12800 as maximum value. Limiting factor was not auto ISO but exposure metering system limitation. This was actually positive finding because camera went way beyond specified metering range.

hwoarang5

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Re: Strange overspec metering results with Canon 5D Mark III
« Reply #25 on: October 18, 2013, 05:42:58 AM »
simplest way.... get a good lightmeter...

bvukich

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Re: Strange overspec metering results with Canon 5D Mark III
« Reply #26 on: October 18, 2013, 09:07:33 AM »
simplest way.... get a good lightmeter...

For one shot, yes.  For a timelapse, that wouldn't help him much.

bvukich

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Re: Strange overspec metering results with Canon 5D Mark III
« Reply #27 on: October 18, 2013, 09:11:45 AM »
I haven't played with the exposure ramping in ML, can it ramp with ISO instead of Tv/Av?  I know it doesn't directly address your issues with metering at extremely low light levels (and an ND... eek) but it may achieve your goal of a smooth timelapse.

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Re: Strange overspec metering results with Canon 5D Mark III
« Reply #27 on: October 18, 2013, 09:11:45 AM »