ArriSun nad Arri M-series

[Szymon Kuriata]

I have a question about Arri Suns and M-series lights

Here I can read that M40 is around 30 % brighter than an AS40 in spot.

So in Arri Photometric app I set:

AS40 with lens spot, 50m distance and I get 1832 lux and Beam Diameter 7.87m

and

M40 spot, Distance 50m and I get 775 lux and beam diameter 15.84m

I know I have bigger beam diameter with M40 so more light in general but is it really 8m difference in diameter makes M40 30% brighter?

What is formula for calculating the 30%?

 

[Ulf Krentz]

It´s not as easy to compare these two units. While the M Series beam diameter can be adjusted by simple turning a knob the AS series had to use different lenses to control the beam. Probably as the M is lensless it is brighter overall, but as you see in your example the AS is much brighter when focussed to a narrow spot, which is for example a characteristic I would not like to miss. The quality of the light fall off is also very different on the AS vs M vs fresnel. Unfortunately as far as I know Arri decided to discontinue the AS line. I don´t know if you are aware, there also is a "conversion kit" available to change the mirror reflector to the PAR reflector (can be done in no time on set) that opens up some options.

 

[Szymon Kuriata]

Thanks Ulf for your time!

I know that the lights are different in light, shadow quality, ergonomic etc.

It's more about photometric

so I did some math:

Difference between 775 lux and 1832 lux is less than 1 EV (based on sekonic conversion chart)

iff M40 is 30% brigther than AS40, even if AS has more lux output, this is becouse two times bigger beam diameter with 775 lux makes more light than lower beam with 1832.

is it correct?

 

[Ulf Krentz]

Not sure how Arri defines a beam diameter as it is a gradient fall off, but yes, 15,84 to 7,87 results in roughly 4x the area (square meter) so 1832lux / 4 is in the ballpark of 70% of 775. Still, for me the main difference is the quality of light, intensity is easily controlled with ND gels (I usually avoid dimming as it introduces a color shift). Cheers!

 

[Ulf Krentz]

snip

so I did some math:

Difference between 775 lux and 1832 lux is less than 1 EV (based on sekonic conversion chart)
snip

It actually is a bit more than a stop (1EV). 1 Stop more than 775 lux would result in 1550 lux. (Just double or half the intensity).

 

[heathfranklin]

i am aware of an as18/m18 conversion kit back/forth but i don't think there is an as or arrisun 40/25 to m40 conversion kit. if there is please link!

 

[Ulf Krentz]

i am aware of an as18/m18 conversion kit back/forth but i don't think there is an as or arrisun 40/25 to m40 conversion kit. if there is please link!

Here you go: Arri M40 to AS40 Conversion Kit L2.37385.0, not sure if there is any Kit to convert the AS to M series though, these kits contain the PAR reflector.
Cheers!

Edit:

I just saw, there also is the Kit vice versa: AS40 to M40 with No. L2.37388.0

 

[serhan nasirli]

I have M18 with AS conversion kit but I have a question
I recently got Arrisun 1.2 Par units but I want to ask that does any of you know that how can I convert them to M- series

There is an AS18 to M-18 conversion kit (like there is M18-to AS18 conversion kit,vice versa)
but do you know that this AS18 to M-18 conversion kit work for Arrisun 12 plus and convert to M Series?

Thank you for in advance