CPL+hood=unnecessary?

Mr Manual · 03-08-2013, 12:33 PM

Good spring evening all,
I have recently been inspired to explore the realm of polarised light. My question is this:
When using a circular polarising filter, is it necessary to also use a hood to prevent flare and maintain contrast or does the nature of the CLP prevent internal reflection?

The lens I will be using the CPL with is the DA40xs which I use with a fastidious plastic mount lens hood. Being only a 27 mm filter thread, I will not be able to reach inside the hood to adjust the CPL and having a plastic mount, detaching and replacing the hood is a pain in the ass!

Many people here say using a hood with the 40xs is not necessary and half the reason I choose to is to protect the front element.

Thank you for reading

,
Jay

JinDesu · 03-08-2013, 12:37 PM

A CPL will block the majority of angled lighting except those that are parallel to the polarizing elements. This does increase contrast. While this is good, the bad is that you lose out on a lot of direct light also, which cuts your exposure by 1 or 2 stops. This, in addition to the loss of image quality in a cheaper polarizer, may mean that a hood may just be better overall.

A CPL will not internally reflect if it is multicoated, I believe.

bdery · 03-08-2013, 01:27 PM

Originally posted by Mr Manual

does the nature of the CLP prevent internal reflection?

To answer that specific part of the question, no. Another glass interface will increase reflections, though you might not see it in every shot. There is no way to decrease total internal reflections by adding glass. You need to remove glass or add coatings.

**dms** · 03-08-2013, 01:27 PM

PL will stop non-polarized (and thus randomly reflected light of a surface if the incident light is polarized) but that does not prevent the filter glass from causing reflections/glare. To reduce that you use the hood.

If anything with the filter (any filter!) the hood is even more necessary, as you have more potentially reflecting surfaces. If the PL was perfect (an impossibility) you still need the hood--it's as though the filter wasn't there.

Na Horuk · 03-08-2013, 02:39 PM

What kind of photography will you be using this for? Since you are using a polarizer you will probably have to take the time to rotate it and stuff anyway, so you might as well shield the lens with your hand or something. Which polarizer are you getting btw? A 27mm one, or are you using step up rings?

Kozlok · 03-08-2013, 03:11 PM

Lens tip did a big CPL study. Some filters cause no change in flare, some make it worse. Review here:

Polarizing filters test - Introduction - Lenstip.com

Mr Manual · 03-09-2013, 02:32 PM

Thank you all for your hasty and well informed responses. If I am to by a CPL, I will probably go with B+W unless the very thorough study Kozlok has referenced gives me reason to choose otherwise. With good glass coming at a good price I would buy a 49mm CPL as I would be able to use it on my M501.7 also. Obviously, doing this would mean getting a 27-49 step-up ring which would also have the advantage of allowing me to use a 49mm hood meaning I could reach inside the hood and adjust the CPL

I live in a seaside town in Cornwall and would be using the CPL to hopefully do justice to the local scenery: deep blue skies and seas with detailed granite rock faces which lose their majesty to haze incurred through distance. I don't intend to shoot orthodox landscapes, more so seaside photography with a human element.

Thank you all again,
Jay
The lips of wisdom are closed, except to the ears of understanding - The Kybalion

**dms** · 03-09-2013, 03:11 PM

A circular hood would likely be fine and would then work for both lenses--and turning the hood would turn the PL.

The standard hood for the 50mm f1.7 should do OK for both. I did not actually try it--but the standard 50mm f/1.4 Nikon hoods work on my 28mm super takumar, so likely OK on the 40mm.

03-08-2013, 12:33 PM	#1
Mr Manual Junior Member Join Date: Dec 2012 Location: London Posts: 32	CPL+hood=unnecessary? Good spring evening all, I have recently been inspired to explore the realm of polarised light. My question is this: When using a circular polarising filter, is it necessary to also use a hood to prevent flare and maintain contrast or does the nature of the CLP prevent internal reflection? The lens I will be using the CPL with is the DA40xs which I use with a fastidious plastic mount lens hood. Being only a 27 mm filter thread, I will not be able to reach inside the hood to adjust the CPL and having a plastic mount, detaching and replacing the hood is a pain in the ass! Many people here say using a hood with the 40xs is not necessary and half the reason I choose to is to protect the front element. Thank you for reading , Jay

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03-08-2013, 12:37 PM	#2
JinDesu Veteran Member Join Date: Jun 2011 Location: New York City Photos: Gallery Posts: 5,638	A CPL will block the majority of angled lighting except those that are parallel to the polarizing elements. This does increase contrast. While this is good, the bad is that you lose out on a lot of direct light also, which cuts your exposure by 1 or 2 stops. This, in addition to the loss of image quality in a cheaper polarizer, may mean that a hood may just be better overall. A CPL will not internally reflect if it is multicoated, I believe.

03-08-2013, 01:27 PM	#3
bdery Pentaxian Join Date: Mar 2008 Location: Quebec city, Canada Photos: Gallery Posts: 9,362	Originally posted by Mr Manual does the nature of the CLP prevent internal reflection? To answer that specific part of the question, no. Another glass interface will increase reflections, though you might not see it in every shot. There is no way to decrease total internal reflections by adding glass. You need to remove glass or add coatings.

03-08-2013, 01:27 PM	#4
dms Site Supporter Join Date: Aug 2011 Location: New York, NY Photos: Gallery Posts: 2,192	PL will stop non-polarized (and thus randomly reflected light of a surface if the incident light is polarized) but that does not prevent the filter glass from causing reflections/glare. To reduce that you use the hood. If anything with the filter (any filter!) the hood is even more necessary, as you have more potentially reflecting surfaces. If the PL was perfect (an impossibility) you still need the hood--it's as though the filter wasn't there.

03-08-2013, 02:39 PM	#5
Na Horuk Veteran Member Join Date: Feb 2012 Location: Slovenia, probably Photos: Gallery \| Albums Posts: 11,186	What kind of photography will you be using this for? Since you are using a polarizer you will probably have to take the time to rotate it and stuff anyway, so you might as well shield the lens with your hand or something. Which polarizer are you getting btw? A 27mm one, or are you using step up rings?

03-08-2013, 03:11 PM	#6
Kozlok Pentaxian Join Date: Jun 2012 Location: Albuquerque Photos: Gallery Posts: 3,148	Lens tip did a big CPL study. Some filters cause no change in flare, some make it worse. Review here: Polarizing filters test - Introduction - Lenstip.com

03-09-2013, 02:32 PM	#7
Mr Manual Junior Member Join Date: Dec 2012 Location: London Posts: 32 Original Poster	Thank you all for your hasty and well informed responses. If I am to by a CPL, I will probably go with B+W unless the very thorough study Kozlok has referenced gives me reason to choose otherwise. With good glass coming at a good price I would buy a 49mm CPL as I would be able to use it on my M501.7 also. Obviously, doing this would mean getting a 27-49 step-up ring which would also have the advantage of allowing me to use a 49mm hood meaning I could reach inside the hood and adjust the CPL I live in a seaside town in Cornwall and would be using the CPL to hopefully do justice to the local scenery: deep blue skies and seas with detailed granite rock faces which lose their majesty to haze incurred through distance. I don't intend to shoot orthodox landscapes, more so seaside photography with a human element. Thank you all again, Jay The lips of wisdom are closed, except to the ears of understanding - The Kybalion

03-09-2013, 03:11 PM	#8
dms Site Supporter Join Date: Aug 2011 Location: New York, NY Photos: Gallery Posts: 2,192	A circular hood would likely be fine and would then work for both lenses--and turning the hood would turn the PL. The standard hood for the 50mm f1.7 should do OK for both. I did not actually try it--but the standard 50mm f/1.4 Nikon hoods work on my 28mm super takumar, so likely OK on the 40mm.