Filters

[Cole Webley]

Tomorrow I am going to be shooting some 2nd Unit work on a short I did recently on S16, I am exploring with some filters I have never used before and I was wondering if someone could help me out with some questions I have.

 

I have tried to find out on Tiffen's website how much stop you lose with some of their filters--but I am at somewhat of a lost. I am wanting to know what your exposure change is for the following filters: Blue 1 SG, Blue 2 SG, Blue 3 SG, Sunset 2 SG, Sunset 3 SG, Coral 5 SG, Cyan 5 SG...since these are grad filters I realize the only stop I am loosing is in the upper part of the frame (supposing that is how I am going to use them) but does anyone know how much? This still applies even though they are color filters right?

 

Thanks guys.

[Jamie Metzger]

I assume that the higher the number, the +1 stop of light loss will be apparent. You should definately be able to check online ( you have such a vast resource) about how much light will be cut.

[Greg Gross]

Look on the filters themselves and see if a filter factor is printed on the edge or on

the ring. I'm not familiar with any of these filters so I don't know if you are using sq-

are drop in filters(for filter holder,shade etc.) or screw on filters. Tiffen has a great

website where you can find a lot of useful information. I'm going to website and take

a look. If I was doing stills I would just bracket and I don't even think about a factor.

I am a student cinematographer but long time professional photographer. I know where

most of my filters shoot and I'm just natrurally used to them. You lose light due to reflec-

ion. I would just normally bracket up a little and down a little when shooting stills. Some-

times I can get a creative effect. If I'm shooting digital I can see right away what I'm get-

ting and often times will also vary W/B to be creative.

 

Greg Gross

[David Mullen ASC]

Generally grads are meant to darken and/or color part of the frame, so you don't want to compensate for their density when shooting. Unless you are stacking two grads, one from above and one from below, with no clear area gap, and need an overall compensation factor -- in which case you could just hold it over your incident meter dome to see how much light is lost.

 

But if you're using a Blue Grad to blue-up a sky more, then don't compensate for the grad's density when exposing.

[Cole Webley]

Great. Thanks guys. I appreciate the quick response.

 

-Cheers

[Greg Gross]

I typed in filter factor for search on Tiffen site but got no results. Went to my American

Cinematographer Manual,pages 194,195:

 

Filter factors are multiples of the un-filtered exposure. A filter factor of "2" is equal to 1

full stop. Example- Three filters of 1 stop each will need three additional stops. In other

words you are using three stacked filters. 2X2X2=8 times the un-filtered exposure. Get

this- you are in the field with no filter factor. Remove the incident bulb(dome) from your

light meter. A flat diffuser may be used but you may leave the sensor bare. Aim it at bri-

ght light source of sufficient intensity. On the ground pointing up at the sky is a good way.

Take a reading with no filter over the lightmeter sensor,be careful not to get your own sh-

adow in the field of the meter. Then make a reading with the filter flat on the lightmeter and

over the sensor. The difference in the two readings is the filter compensation for that filter.

Don't forget though you may run in to some unusual circumstances. Info here was taken fr-

om American Cinematographer Manual pages 194,195.

 

Greg Gross

[Cole Webley]

Thanks Greg. That was my default option but since the light wasn't in the position it is going to be tomorrow when we shoot I figured I would cut corners and ask someone on the forum.

 

This is why I love the forum, everyone is so willing to help.

 

Keep up the good work.

 

Cheers.

[Greg Gross]

Thank you Cole,

My brother went to BYU,he's a computer designer.

Always asking me how to take good pictures!

 

Greg Gross

[Mario C. Jackson]

One trick I always use to figure out how much light is lost by a filter is by using my light meter. I take an ambient reading without the filter and then place the filter over my meter and take another. That will tell you how much light you lose with the filter.

Hope this helps

Mario Concepcion Jackson

[John Pytlak RIP]

One trick I always use to figure out how much light is lost by a filter is by using my light meter. I take an ambient reading without the filter and then place the filter over my meter and take another. That will tell you how much light you lose with the filter.

Hope this helps

Mario Concepcion Jackson

 

Using a light meter to measure the attenuation of a filter is a good method, as long as the meter is one designed for having a photographic response.

 

You can also measure the densities of the filter using a color densitometer -- that will give you a good idea of how much red, green and blue light the filter absorbs. Remember 0.30 density = 1 stop.