EFFECT OF USING ND FILTER QUESTION????

Daniel Porto · September 3, 2008

What is the different between shooting at F5.6 or shooting at F4.0 and using a ND2 Filter, apart from the depth of field changing???? Does the more glass you have in front of a lens affect teh quality, or increase the chance of a lens flare????

I have had some confusion trying to work this one out for myself so I thought why not ask in the forums!!!

Thanks

Adrian Sierkowski · September 3, 2008

well it's be an ND.3 firstly, to cut the 1 stop of light. Primarily it'll change the DoF, though the more glass you have the more chance of reflections you might get; don't know 'bout flare, though, honestly. Also, there is a change to the MTF if I'm not mistaken, marginally changing the overall resolution. . . but it's pretty minute.

Point being, if you have 5.6 of light, but you need a 4, you throw on a filter, because it's much easier to do that than mess with shutters etc. . .also that'd change the image a lot more.

James Steven Beverly · September 4, 2008

MTF? Never heard that thar term.

Dan Goulder · September 4, 2008

What is the different between shooting at F5.6 or shooting at F4.0 and using a ND2 Filter, apart from the depth of field changing???? Does the more glass you have in front of a lens affect teh quality, or increase the chance of a lens flare????

I have had some confusion trying to work this one out for myself so I thought why not ask in the forums!!!

Thanks

Most lenses will perform equally and consistently well at both those stops. I wouldn't bother to use an ND at that stop (T5.6) unless I needed or wanted to match or intercut that footage with other footage that had been shot at T4.

Adrian Sierkowski · September 4, 2008

MTF refers to Modular Transfer Function sometimes called, IIRC, Modulation Transfer Function, it deals with resolution and is multiplied together, therefore, the more "stuff" you put in an optical path the less it can resolve, essentially and at least to my understanding. . . they go into it a bit here, but it's always been a murky concept to me:

http://en.wikipedia.org/wiki/Optical_resolution

Panavision's Demystifying Digital Cinema goes into it as well in video:

http://www.freshdv.com/2008/05/demystifyin...mera-specs.html

Daniel Porto · September 4, 2008

well it's be an ND.3 firstly, to cut the 1 stop of light. Primarily it'll change the DoF, though the more glass you have the more chance of reflections you might get; don't know 'bout flare, though, honestly. Also, there is a change to the MTF if I'm not mistaken, marginally changing the overall resolution. . . but it's pretty minute.
Point being, if you have 5.6 of light, but you need a 4, you throw on a filter, because it's much easier to do that than mess with shutters etc. . .also that'd change the image a lot more.

THANKYOU FOR YOUR CORRECTION ADRIAN

Andrew Koch · September 5, 2008

well it's be an ND.3 firstly, to cut the 1 stop of light. Primarily it'll change the DoF,

Adding an ND 0.3 does not change the depth of field. Opening up a stop to compensate for the ND 0.3 will make the depth of field more shallow. I think this is what Adrian meant, but I just wanted to make sure that was clarified.

Adrian Sierkowski · September 5, 2008

Andrew, that is exactly what I meant. Sorry for not being 100% clear on that. ND, in and of itself, doesn't do anything but decrease the amount of light entering the camera. Therefore, the compensation for this, opening up 1 stop on an ND.3 in this case is what will alter the Depth of Field. No compensation will just result in an image which is underexposed by 1 stop.