Shutter Open angle different from 180°

[Thomas Masper]

In the instruction manual of of my light meter (L508 Zoom Master), I read that in cine mode the exposure value are showed for standard shutter open angle of 180°.

If I need different angle I have to change ISO (+1/3 for 220° and -1/3 for 160°).

 

I think that this is quite OK for 220 angle: (220/180)=1.22 time the 180° exposure,

that is about log2(1.22)=0.29----->+(0.86/3) instead of +(1/3).

 

But for 160° I have (160/180)=0.88 time the 180° exposure,

that is log2(0.88)=-0.17---->-(0.5/3) instead of -(1/3)!!!!

 

log2(x) means base 2 log.

 

Is that correct or I made some mistake?

 

Thanks

Thomas

[stijnbarbe]

doens't the 508Zoommaster have a shutter angle change function?

 

If not, I use another trick. I devide the shutter angle by the product of 360 and framerate. For example: a shutter down to 90° at 25fps gives me a fotographic shutter speed of 1/100 (90°/360*25=90/9000). This is 1 stop faster than a standard shutter setting of 172.8° (or as you use 180°) This trick works very good for standard shutter settings like 135°, 90°, 45°,...

I learnt this trick when I only had my analog needlemeter, the L-398M. You can forget all about shutter compensation on that one.

Sure you can change your ISO-value according to your filters an shutters, but I tend to keep filtercompensation and shuttercompensation seperate for overview.

 

But what you stated in your post is correct, A 40° in- or decrease is up or down 1/3 of a stop. (slightly less, but hell)

[Michael Nash]

I have the 508 and it does allow you to program different shutter angles, from 5 deg. to 270 deg. in 5 deg. increments. Hold down the MODE button and the ISO2 button, and turn the SET/CHANGE dial to the desired angle. "Ang" will appear in the display along with the angle.

[Thomas Masper]

Thanks a lot!

The 508 ZoomMaster has not the possibility of change the angle, the version called "Cine" can do this (but I'm quite sure that the two light meter have the same electronics and that this function is only software!).

I'll use yours trick in my future works!

 

Bye

Thomas Masper

[Guest oscar]

IT'S KIND OF FUNNY, AFTER THIS ALL IN ONE COMBOS WERE BROUGHT INTO MARKET, AND AFTER THE "CINEMETER" , I DO RECALL MY FAVORITE METER THE "SPECTRA - CINE" BUT ALL CALCULATIONS WERE DONE IN DA HEAD, LOWERING OR ADDING ISO NUMBERS, WHATEVER HAPPENED TO MENTAL DRIVEN MATH CALCULATIONS DONE IN THAT SAME LITTLE 5 SECONDS WHEN YOU WERE SHOOTING? IT'S SOMEWHAT LIKEWISE KIDS THAT NO LONGER KNOW HOW TO CLIMB A TREE, RATHER BE PLAYING X-BOX OR NINTENDO. JUST A MELANCOLIC RECALL, NOTHING BAD

[stijnbarbe]

WHATEVER HAPPENED TO MENTAL DRIVEN MATH CALCULATIONS DONE IN THAT SAME LITTLE 5 SECONDS WHEN YOU WERE SHOOTING?

 

true, but then again, some of those nintendo-kids leter become technology-whizzes that save your shot on the scanner or make incredible 3D-cgi footage. ;)

 

But it's best to have a bit of both. undersanding the logic of adding and taking away light and compensating in ISO-value on a simple lightmeter helps understanding a state of the art lightmeter.

 

Hold down the MODE button and the ISO2 button, and turn the SET/CHANGE dial to the desired angle.

yes, so it says on the back, but don't forget it has to be in 'cine mode' for that. Since I use a borrowed 508cine I had a hell of a time experimenting with those jumperswitches behind the batt. panel. :blink:

But it's working just fine now.