Arsat/Zodiak 30/3,5 filter compensation

[dweezil]

Hi, <p>

 

I have recently aquired the Arsat/ Zodiak 30 mm fisheye and since I have no

manual<p>

I was wondering what the needed compensation is for the various filters that are

delivered with the lens.<p>

 

I've searched and can't seem to find anything about this.<p>

 

Regards,<p>

 

Erwin<p>

[q.g._de_bakker]

You do not have the manual, but you do have the filters themselves, right?<br>Have a look at what it says on their rims.<br><br>The factors you'll find printed there are aperture factors, with "1.4x" being equal to a "2x" shutterspeed factor, or 1 stop, and "2.8x" being equal to a "4x" shutterspeed factor, or 2 stops.

[dweezil]

I bought the lens 2nd hand and it came in a case with the filters but no manual and I could not find one on the net.

I had seen the markings on the filters but could not figure it out. thanks for the info.

[richard_p]

A 2 factor is equal to 2 f stops (4x). A 2.8 factor equals to 3 f stops (8x).

 

 

Richard

[q.g._de_bakker]

???<br>That's not right either. ;-)<br><br>The measured values (i hadn't put them in front of a meter before) are closer to an interpretation of the factors as being shutterspeed factors after all.<br>The "1.4x" printed on the filter then corresponds to 0.5 stop, the "2.8x" factor to 1.5 stop.<br><br>A factor will never equal the number of stops, Richard.<br>Unless you assume that they didn't mean the figures to represent factors to begin with, and the little "x" they put behind the figure on the rims is there in mistake.<br>So a factor of 2.8 either equals log(2.8)/log(1.4) = 2 stops (with 1.4x being the step size separating two aperture stops) or log(2.8)/log(2) = 1.485... stops (2 being the step size separating two shutterspeed stops).

[johan_de_groote]

Thanks for that info. I also bought one last weekend. Really a wonderfull lens.