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Best aperture for a Lens

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mark thompson
Best aperture for a Lens
on Oct 28, 2018 at 8:01:52 am

I've been using camera side tools to check exposure (Zebras, False Color, gray card, etc.) which are all designed to not overexpose the sensor. At a camera talk/demo someone mentioned that their challenge was getting the lens set to it's best aperture. A lens has an aperture which offers the sharpest picture and best color.

To me that sounds like a conflict. Aperture being to best tool to adjust exposure.

How do you juggle those potentially conflicting requirements?

I'm looking to listen any experience people have or any good articles references.

I have searched and there are articles about the best aperture for a lens but I've not found any that discuss how that is used on set to get the best pictures.
tia


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Rick Wise
Re: Best aperture for a Lens
on Oct 28, 2018 at 2:45:59 pm

I have never paid much attention to "best aperture" for a lens other than paying attention to the fact that many lenses will give you crisper images if they are NOT wide open OR stopped all the way down. But let's say your particular lens has an especially sweet spot at f/4 and you want to take advantage of that. You've metered the scene and the f/stop is f/8. The only way you can expose at f/4 is cut the light intensities of your lights so that now your exposure is f/4. In other words, cut down the light intensities of your key lights (and probably all others as well) by 2 f/stops.

You control light intensity so that you can expose at your desired f/stop. Actually, we do that all the time to keep the look of a complete scene constant. If we shoot one shot at f/2 and then shoot another shot that will be cut in directly after the first shot, we work to make the 2nd shot also an f/2, etc., so that depth of field characteristics remain constant and also the background intensities don't change. In fact, we try to keep ALL the shots within the scene at f/2 for those two reasons. (We do fudge a bit when necessary, but strive for a constant f/stop throughout the scene.)

Rick Wise
Cinematographer
MFA/BFA Lighting and Camera Instructor Academy of Art University
San Francisco Bay Area
http://www.RickWiseDP.com


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mark thompson
Re: Best aperture for a Lens
on Oct 29, 2018 at 4:23:15 pm

Rick,
thanks for the reply. I'm glad that you don't consider it a major issue!

I shoot mainly on Sony gear and the advice they give seems to be "light your scene" and then use gray cards and zebras to make sure exposure is set correctly. Of course the people I talk to are sales and consultants - not so many DP.

I was at another meeting (mainly broadcast camera people) where one topic discussed was their lack of enthusiasm for the dslr cameras. Not that there was anything wrong with the camera but rather those cameras are used fully open and producers like that look. So they feel pressured to shoot with the lens wide open even though they don't feel it gives them the best picture.


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Bouke Vahl
Re: Best aperture for a Lens
on Oct 30, 2018 at 9:05:45 pm

I once had the honour to go to movie followed with a Q&A with Robby Müller.
It was a shocking experience.

Mr. Müller, on movie X you worked with stock Y, why did you pick it?
-Well, the producers wife had a few boxes left under her bed.

Mr. Müller, on movie X you used camera Y with lens Z, how did you make the decision to use that?
-Well, that was the equipment present on set, either the last or the cheapest ones available at the rental shop.

And the anecdote:
'Mr. Müller, we would like you to shoot our next movie, and we want you to be as creative and original as you always are, do something totally new, and make it look exactly like Paris Texas.'

As any photographer will tell you, the best camera is the one you have on you.

(Kidding aside, don't trust anything but your eyes. Be experienced with looking in the viewfinder and review on a real monitor back home. A good dP can expose based on what his eyes tell him when he looks at the set.
And the most important if you shoot with any form of LUTS, don't do it unless you REALLY KNOW WHAT YOU ARE DOING. It will NOT be better in almost all of the cases I've seen, and I'm not in the wedding video industry.)

Bouke
http://www.videotoolshed.com


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