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04-24-2011, 02:33 AM   #1
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ND filter vs Polarizers

Ive been reading to identify what I really need to have considering also the valuable adices from veterans about limiting the usage of filters.
Now I know, if given a change we can use UV filters just as a protector for the lens but some also say that the hood does a protecting job as well.
I want to decide between ND and Polarizer been reading lots and lots of views from fellow members, I know this area is very personal so I am not asking do I need it? instead I want to know a bit more so I can decide what I must do next.
I summarize my understanding on these two as:
ND filter: to cut down light (in other words will this not improve the saturation?)
Polarizer: to increase saturation and cut down reflections.
Having said that, I welcome the seniors to tell me whether
1. ND can do the job of a Polarizer as well or vice versa?
2. Is there an option of a filter that does the job of both instead of getting both the filters?
3. Between a square ND filter and a circular what are the drawbacks in these two if any compared with the other.
4. graded ND vs normal ND pros and cons?
Sorry for the many questions in one post.

04-24-2011, 07:07 AM   #2
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QuoteOriginally posted by sany Quote
ND filter: to cut down light (in other words will this not improve the saturation?) Polarizer: to increase saturation and cut down reflections.
The "N" in ND stands for "Neutral" - in other words it doesn't (or shouldn't) do anything besides reduce the amount of light entering the camera. I say "shouldn't", as poor-quality ND filters can alter the tonality.

A polarizer polarizes light - depending on how it's oriented it can either enhance or reduce saturation outdoors, or enhance or reduce reflections from glass/water. You put it on your lens, and rotate it to get the desired effect. Like an ND filter, all polarizers reduce the amount of light entering the camera (typically 1 to 1.5 stops.)

An ND filter is used when you have too much light coming in for your selected shutter speed and aperture, and you can't reduce your ISO. They come rated in EV (for how many stops of light they absorb.)

QuoteOriginally posted by sany Quote
1. ND can do the job of a Polarizer as well or vice versa? 2. Is there an option of a filter that does the job of both instead of getting both the filters?
An ND can't do the job of a polarizer, but a polarizer works as a mild ND (again, typically 1 to 1.5 stops.)

QuoteOriginally posted by sany Quote
3. Between a square ND filter and a circular what are the drawbacks in these two if any compared with the other.
You can't fit a lens hood around a square ND.

QuoteOriginally posted by sany Quote
4. graded ND vs normal ND – pros and cons?
There are no "pros" or "cons", they are two different tools for two different jobs. You might as well ask about the pros and cons of colour gel vs on-camera flash, or polarizing filter vs macro lens.
04-24-2011, 10:05 AM   #3
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QuoteOriginally posted by Karl Stevens Quote
The "N" in ND stands for "Neutral" - in other words it doesn't (or shouldn't) do anything besides reduce the amount of light entering the camera. I say "shouldn't", as poor-quality ND filters can alter the tonality.

A polarizer polarizes light - depending on how it's oriented it can either enhance or reduce saturation outdoors, or enhance or reduce reflections from glass/water. You put it on your lens, and rotate it to get the desired effect. Like an ND filter, all polarizers reduce the amount of light entering the camera (typically 1 to 1.5 stops.)

An ND filter is used when you have too much light coming in for your selected shutter speed and aperture, and you can't reduce your ISO. They come rated in EV (for how many stops of light they absorb.)



An ND can't do the job of a polarizer, but a polarizer works as a mild ND (again, typically 1 to 1.5 stops.)



You can't fit a lens hood around a square ND.



There are no "pros" or "cons", they are two different tools for two different jobs. You might as well ask about the pros and cons of colour gel vs on-camera flash, or polarizing filter vs macro lens.

As far as lens hoods go, if you're using the Cokin system of square filters, they make snap-on hoods that clip onto the outside of the filter holder. They're only about 3/4 inch long, but they're stackable, so you can use as many or as few as you wish.

Another difference between a ND and a polarizer is that the polarizer may not affect all of the image in the same way. Polarizers work best when used at 90 degrees from the light source. If you're shooting a sky with a wide-ish lens, this may result in much more polarization (and darkness) on one side of the sky than on the other. A ND filter will affect the image uniformly.
04-24-2011, 10:08 AM   #4
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Here is a great quick reference with sample photos.

Photographic filter - Wikipedia, the free encyclopedia

In addition, a polarizer does not polarize light....it blocks light that is polarized in one direction. Most effective filtering occurrs when shooting 90 degree angle to the Sun.

Square (Cokin style) filters have their own square hoods that can be attached to the filter holder. Many photogs just use their hat to block direct light from hitting the filter.

Thats all I can add to what Karl already covered pretty well for you.

EDIT: and NOBLEPA snuck in one of my tidbits while I was busy typing

04-25-2011, 06:44 AM   #5
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QuoteOriginally posted by imtheguy Quote
In addition, a polarizer does not polarize light....it blocks light that is polarized in one direction. Most effective filtering occurrs when shooting 90 degree angle to the Sun.
D'oh! Yes, you are entirely correct - I don't know what I was thinking when I wrote that. Thanks for the correction!
04-25-2011, 09:53 AM   #6
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Hello Sany, in (43) years of Pentax SLR / DSLR photography I have not felt a pressing need for ND Filters ever. But a CPL was always useful. I bought the best CPL's in 72 and 58 mm dias + some step up/down adapters so that I could use them on all my lenses.
And have always used Pentax SMC Filters on my lenses - they have saved my lenses on more than half a dozen occasions - in our weddings, girls have fun by raining all kinds of gooey stuff on you.
My lenses are never without a hood - have a variety of collapsible rubber ones including the hard to find wide angle types. These too have saved my lenses - once when it landed on the rubber - our floors are marble and no carpets.
04-25-2011, 10:00 AM   #7
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Hi Nanhi, can you suggest where I can get those different hoods you just mentioned and the adaptors for the polarisers. thanks all
04-25-2011, 10:43 AM   #8
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Sany, I bought the rubber collapsible hoods and the step up/down rings (Delhi make stuff - Sonia, Shine, etc) from local photography shops - most for $ 2 or 3.
The wide angle rubber hood was purchased in Singapur for US $ 13 - my friend was cheated. Bought the CPLs and SMC Filters from photo shops in Muscat, Oman.
But you can find all these stuff on a Google search and eBay - India/USA, Amazon, Photodiox, Gadget Town, etc
Two use-full accessories for macro photography are a) Lens Reversal Adapter - $ 4 to 5, b) Macro Extension Tube set $ 10 to 13.
The lens mount on the Extension Tube double up for testing various adapters and manual lenses I buy, before putting them on my expensive camera bodies.

04-25-2011, 08:29 PM   #9
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I see several advantages of the square filters over the round ones:
1) one set of filters, many lenses, using cheap adapter rings
2) fewer issues with vingnetting stacking filters, which I do sometimes to get long exposures
3) if you are using a graduated filter you have some latitude to slide it up and down in the older to get the graduation where you want it
04-26-2011, 03:49 AM   #10
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QuoteOriginally posted by sany Quote
4. graded ND vs normal ND – pros and cons?
These also are two different topics, not comparable.
As breifly hinted at by cats_five, a graduated neutral density effects different parts of a single image differently, whereas a "normal ND" effects the entire picture evenly. The purpose of the grad ND is (typically) to darken a too bright sky. The rectangular grad ND is best at this because you can move the graduated area out of the center of the photo to align with your chosen location for the "horizon".
04-26-2011, 05:31 AM   #11
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It seems that you are new to the filter world (outside of UV filters). When i first started myself in the dslr world, i bought insane amounts of UV filters, (one for each lens), and a few polarizers. Since then, i've realized that UV filters are near worthless and the polarizers are indispensible for what they do. By far my favorite type of filter for improving certain types of photos. On that note, I also own an ND8 for the few times I take a waterfall pics.
04-27-2011, 09:22 AM   #12
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QuoteQuote:
=calicojack;..... The rectangular grad ND is best at this because you can move the graduated area out of the center of the photo to align with your chosen location for the "horizon".
Is there some kind of grip when you slide vertically as pointed by you above to hold it in a position desired?
Also Gatorpentax and cats_five and all others (considering Gatorpentax earlier day experience with various makes of filters) can you please suggest 1-2 best of the line companies that produce the square filters. I am not sure whetehr Hoya has one, but have heard cokin, how are they compared to hoya. Are we able to rotate the square polarizer like the circle one and I read somewhere that the polarizer has two elements in it - how is the square one built in that respect.
GatorPentax - when you say ND8, is it the one that has 8 stops? with these square ND filter when you want to achieve 2 stop down is it that we stack two individual filter plates in or it can be achieved using even a one filter?

thanks once again all. You guys rock!
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