Multiple polarizing filters? - DPChallenge Forums

Canon EF-S 10-22mm f/3.5-4.5 USM

06/23/2010 04:50:26 PM · #1

As some may have seen my previous posts, I am going to Montana for a vacation with my mom and dad. I was thinking of making this one VERY big photo opportunity for me. I have a question that may be kinda dumb but I just now thought of it.

I have heard of people using a darker filter for making the shutter speed slower for say a waterfall in bright lighting. Could I possibly use multiple polarizing filters for this? Reason I am saying this is because wouldn't this give me more control on the amount of light coming in? For example if I wanted a REALLY slow shutter I could put maybe 4 filters on it to make is nice and dark but if I wanted something sorta slow I could put maybe just 1? Does this make sense and does anyone use this technique?

mycelium

Canon EOS-350D Rebel XT

06/23/2010 04:51:34 PM · #2

Sure, that would work, but more glass between your sensor and the outside world means a softer image and more chromatic aberration.

Canon EF-S 10-22mm f/3.5-4.5 USM

06/23/2010 04:54:48 PM · #3

So I should get a darker one? Again this is all just a thought that I had. Is it more expensive to get one of these?

mycelium

Canon EOS-350D Rebel XT

06/23/2010 04:59:02 PM · #4

I don't know anything about pricing, but that should be easy to find out.

You'd definitely be better off with a single filter than with four.

If all you want to do is take longer exposures--i.e., you don't need the polarizing--just get an ND filter. Should be much cheaper than a polarizer.

PGerst

Canon EOS-20D

Tamron SP AF 28-75mm f/2.8 XR Di for Canon

06/23/2010 04:59:04 PM · #5

I always wondered about this too. Why buy multiple ND filters when you can take 2 polarizing filters and turn them to adjust the opacity. At 90Â° you will block out almost all the light. BUT, they need to be linear, not circular.

Canon EF-S 18-135mm f/3.5-5.6 IS STM

06/23/2010 04:59:31 PM · #6

This could work, and work damn well actually.

So, what you'd need is two polarizers (I'm not sure if CPL will work, you'll need to try that, I know that linear polarization works, for further study see here)

The idea is that you will cause the light to go "extinct" as you rotate both (linear, maybe circular) polarizers to a 90 degree opposition, you will see 0 light transmission, then it will rapidly increase as you move away from that position.

This is a really good idea for a variable ND filter.

-Cory

hawkeyefilms

Canon EOS-550D Rebel T2i

06/23/2010 05:09:20 PM · #7

Knock yourselves out Vari ND Filter

06/23/2010 05:13:54 PM · #8

Originally posted by hawkeyefilms:

Knock yourselves out Vari ND Filter

And quite cheap too huh? ($350-$400).. That's insane.. Singh-Ray might be killer, but their prices are murder!

Message edited by author 2010-06-23 17:14:37.

Canon EF 24-105mm f/4.0L IS

06/23/2010 05:20:38 PM · #9

Hmm you lost me, I am not that big into filter. So this is what I think I am getting here. The NP filter is something like gradient in Photoshop... so far so good?

90Â°? What are you talking about here?

Also what is the difference between linear and circular? This is the difference in shape of the actual glass yes? For example squared filters are the linear and circular is the "O" shaped one correct?

And what would 2 ND filters do? I am sorry if this is sorta annoying trying to teach a newbie about filters. Haha!

scalvert

Canon EOS-5D Mark III

06/23/2010 05:33:13 PM · #10

I think multiple circular polarizers might create unsightly interference patterns. Linear polarizers won't, but they screw up DSLR metering. Neutral density filters tend to be cheaper than polarizers anyway, so just stack one ND with a circular polarizer and you should be all set. An ND8 (0.9) will reduce the light by 2.8 stops (87.5%), and the polarizer will knock off another stop.

scalvert

Canon EOS-5D Mark III

Canon EF 24-105mm f/4.0L IS

06/23/2010 05:39:25 PM · #11

Originally posted by mbrutus2009:

Also what is the difference between linear and circular? This is the difference in shape of the actual glass yes? For example squared filters are the linear and circular is the "O" shaped one correct?

No, it's the shape of the diffraction pattern. Linear polarizers are used for video or manual focus cameras. Circular polarizers are required for DSLRs.

Originally posted by mbrutus2009:

And what would 2 ND filters do?

It's just a piece of tinted glass. More ND filters = less light, however stacking multiple filters means you're shooting through a longer "tube" of glass and you'll get dark vignetting around the edges of photos taken with wide angle lenses.

Olympus 14-42mm f.3.5-5.6 ED Zuiko Digital Zoom

06/23/2010 05:55:11 PM · #12

So let me get this straight before I go to my next question. ND filters are gradient filters sorta? Dark on one side clear on the other... I hope I am getting this correct. Haha!

e10icus

Olympus E-500 EVOLT

06/23/2010 06:00:40 PM · #13

ND = Neutral Density.

Just makes things darker, doesn't change the colors in any way. I think you can get gradient neutral density filters for shots where you have a super-bright sky with a dark(er) foreground, for instance.

06/23/2010 06:02:03 PM · #14

Originally posted by mbrutus2009:

So let me get this straight before I go to my next question. ND filters are gradient filters sorta? Dark on one side clear on the other... I hope I am getting this correct. Haha!

That would be a graduated ND filter.... They also make solid ND filters.

06/23/2010 06:05:08 PM · #15

OHHHHHHHHH I get it now!!! Ok, this makes sooo much more sense now!! Haha! I thought it was ONLY a gradient type filter. But now that it has been said that it can be just a dark glass it makes sense. Thanks for clearing it up for me! :) I have ONE more question.

I am looking and looking and looking... What should I get?

Just one ND filter? A few of different shades? One dark one and just use my polarized filter that I have now? Or maybe should I get one that is a gradient type? Any thoughts? I am looking to spend about 50$ I think.

06/23/2010 06:07:08 PM · #16

Originally posted by mbrutus2009:

For $50? Get a single solid dark ND filter.

06/23/2010 06:14:36 PM · #17

FWIW, in order to shoot a waterfall and get that "smooth" appearance in bright light, you'll need nearly ten stops of darkening. While that's possible (10-stop ND filters are available), you won't get there for $50. If you can live with much shorter exposures, a 3-stop filter can probably be had for that price, at least if your filter size is not too large.

06/23/2010 06:22:27 PM · #18

Filter

This is 8 stops for about 25$. Would this be a good buy?

Nikon AF Nikkor 50mm f/1.8

06/23/2010 06:24:43 PM · #19

Originally posted by mbrutus2009:

Filter

This is 8 stops for about 25$. Would this be a good buy?

Careful, it's 8x, which is three stops. Remember, 1 stop is 2x, 2 stops is 2*2 or 4x, 3 stops is 2*2*2 or 8x...

Gordon_1

Nikon D300

06/23/2010 06:26:22 PM · #20

This was taken with a 10 stop ND filter

06/23/2010 06:51:47 PM · #21

Originally posted by kirbic:

Originally posted by mbrutus2009:
Filter

This is 8 stops for about 25$. Would this be a good buy?

Careful, it's 8x, which is three stops. Remember, 1 stop is 2x, 2 stops is 2*2 or 4x, 3 stops is 2*2*2 or 8x...

So I would need a 2*2*2*2*2*2*2*2*2*2? Thats alot of 2's!!! HAHA

O.k. So how about me getting a 3stop one? Will that do? Or will I need a 10stop one?

06/23/2010 07:10:24 PM · #22

Originally posted by mbrutus2009:

So I would need a 2*2*2*2*2*2*2*2*2*2? Thats alot of 2's!!! HAHA

O.k. So how about me getting a 3stop one? Will that do? Or will I need a 10stop one?

Yes it is a lot of 2s! It means that only about 0.1% of the light gets through. In practical terms, that means a *very* dark viewfinder, with the image just barely visible even on a bright day.
to answer the question as to whether you need a 10-stop filter, look at

toddster45's post. He exposed for 0.8 seconds at f/5.6, and that is with a 10-stop filter. Bottom line is, with a 10 stop ND filter you can achieve between 10 and 30s exposures at ISO 100, f/16 in bright daylight. With a 3-stop filter, your longest exposure will be about 1/15s or so. Not very long. Stacking two 3-stop filters will get you to about 1/2 second.
So in the end, if you want multi-second exposures in bright daylight, a 10-stop filter is invaluable... but it will be a little tricky to use.

06/23/2010 07:17:32 PM · #23

I can't seem to find one? Any help? I just want to know the price for it for a 52mm lens size.

I cant seem to figure out which one is which when I search for it.