5D mark III motion blur

[Grabshot]

I attemped to shoot a motion blur time lapse at 1/2sec on shutter priority outside in sunlight (back to the sun). Used a variable ND filter and adjusted it to get a reasonable f-stop. The f-stop never changed. The camera remained at a flashing f 36 even at full extinction. I then covered the lens and it remained at f 36, blinking even when getting no light as long as the shutter was set on 1/2 sec. The f 36 blinking wouldn't stop until I set the shutter priority up to 1/10 sec.  As you'd expect, when the F-stop was at f-36 the shots came out extreemly underexposed.

Does this make any sense??

[Ray-uk · Accepted solution]

Variable ND filters are generally not much use and of varying quality and of varying maximum density, although it appears completely black to your eyes it's probably not, most seem to be about 6 or 8 stops at the darkest end.

I would suggest that you would need a 10 or 12 stop ND filter to do what you are trying and don't rely on the meter reading with the filter fitted.

Set your camera to manual, take a light reading without the filter then fit the filter and make the appropriate adjustment by subtracting the strength of the filter.

Don't forget to cover the eyepiece of the viewfinder especially if it is facing the sun otherwise you will never get a correct reading.

[Ray-uk · Accepted solution]

Variable ND filters are generally not much use and of varying quality and of varying maximum density, although it appears completely black to your eyes it's probably not, most seem to be about 6 or 8 stops at the darkest end.

I would suggest that you would need a 10 or 12 stop ND filter to do what you are trying and don't rely on the meter reading with the filter fitted.

Set your camera to manual, take a light reading without the filter then fit the filter and make the appropriate adjustment by subtracting the strength of the filter.

Don't forget to cover the eyepiece of the viewfinder especially if it is facing the sun otherwise you will never get a correct reading.

[Grabshot]

First time on this forum... better late than never. Good advice quickly.

Thanks. You've given me some things to try. I've recently become enamored with time lapse of crowds put to music.

Thanks again,

Jerry

[Waddizzle · Accepted solution]

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@Grabshot wrote:

Does this make any sense??

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It makes sense to me.  When you see exposure settings flashing in the viewfinder, that means that the exposure is way over or under.  The camera will flash the setting it thinks needs to be corrected.

The fact that the shot may have come out pretty underexposed is normal, too.  I do not know the specification on the flashing exposure warnings, but the camera allows you to dial iin +/- 3 stops of exposure compensation.  And, the camera does not flash Han exposure warning at you in the viewfinder.  

I would conclude that the flashing means exposure is off by at least 3 stops.  The camera stopped flashing when the exposure was inside of the  window of +/- 3 stops.  Just because the flashing stops, does not mean the exposure is correct.