Lens Filters
- Thread starter NoJobTog
- Start date
Flaca Productions
Well-known member
polarizers can be very helpful in removing glare, saturating colors and can really make some images pop. but there are a couple of items to remember:
- you have to rotate a polarizer to "activate" it, so a screw-on can be a bit cumbersome and slow to work with (as opposed to one in a matte box) as you'll have to reach into the lens hood to rotate.
- it'll take anywhere from 1/2 to nearly a full stop of light away, so you won't want to leave it on all of the time - especially during most indoor interviews or low-light situations. this, however, can also be a plus when shooting in bright daylight which is also when you're most likely to use a polarizer. (however, they do also make low-light polarizers that don't take away so much light.)
- if you're on a particularly wide lens, be sure to get a thin filter to avoid vignetting. screw-on polarizers tend to be somewhat thicker to give you the surface area around the edge to rotate it with your fingers, but they do make thin/wide-angle versions.
in short, they are a great tool that can be a 'secret weapon' but are generally not for all-the-time use and/or full-time replacement of your clear filter.
- you have to rotate a polarizer to "activate" it, so a screw-on can be a bit cumbersome and slow to work with (as opposed to one in a matte box) as you'll have to reach into the lens hood to rotate.
- it'll take anywhere from 1/2 to nearly a full stop of light away, so you won't want to leave it on all of the time - especially during most indoor interviews or low-light situations. this, however, can also be a plus when shooting in bright daylight which is also when you're most likely to use a polarizer. (however, they do also make low-light polarizers that don't take away so much light.)
- if you're on a particularly wide lens, be sure to get a thin filter to avoid vignetting. screw-on polarizers tend to be somewhat thicker to give you the surface area around the edge to rotate it with your fingers, but they do make thin/wide-angle versions.
in short, they are a great tool that can be a 'secret weapon' but are generally not for all-the-time use and/or full-time replacement of your clear filter.
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Ben Longden
Well-known member
Yep. I agree with Brian.
A Polariser is a great investment, but leaving it on all the time WILL reduce the light input to the camera. Its the same as using a ND filter. My tests show its about 2 stops.
So, in night and indoor shoots, leave it off. If you want orgasmic blue skies with wide angle scenery on a sunny day, leave it on.
Also, seeing as its a defacto ND, you can use it to assist with shallow depth of field control. That is you can use it with your inbuilt NDs to have the camera at a wide as possible iris, to get the blurry background effect you need, say, for an interview situation.
The best filter to buy is a plain clear, optically flat one as a lens protector and cheap insurance. The next best is the Polariser, and to control skies, a graduated ND.
I have a drawer full of various filters, colours, grads and effects, and found that while they can be used creatively, the really effective ones to have on hand are the holy trinity itself; Polar, ND grad and a clear.
By the way, a polar comes into its own when used wide angle, and when the subject is about 90 degrees to the light. Go outside on a sunny day with one in hand, and you will soon see what I mean. Using it on a tele setting really only serves an ND function.
HTH
Ben
A Polariser is a great investment, but leaving it on all the time WILL reduce the light input to the camera. Its the same as using a ND filter. My tests show its about 2 stops.
So, in night and indoor shoots, leave it off. If you want orgasmic blue skies with wide angle scenery on a sunny day, leave it on.
Also, seeing as its a defacto ND, you can use it to assist with shallow depth of field control. That is you can use it with your inbuilt NDs to have the camera at a wide as possible iris, to get the blurry background effect you need, say, for an interview situation.
The best filter to buy is a plain clear, optically flat one as a lens protector and cheap insurance. The next best is the Polariser, and to control skies, a graduated ND.
I have a drawer full of various filters, colours, grads and effects, and found that while they can be used creatively, the really effective ones to have on hand are the holy trinity itself; Polar, ND grad and a clear.
By the way, a polar comes into its own when used wide angle, and when the subject is about 90 degrees to the light. Go outside on a sunny day with one in hand, and you will soon see what I mean. Using it on a tele setting really only serves an ND function.
HTH
Ben
NoJobTog
Well-known member
Thanks Guys, I really appreciate it. The only time I have used a polarizing filter is on my DSLR. You guys brought up some great things to think about.
As far as the graduated ND filter goes, under what types of situations is that good for? I am also curious about how it affects depth of field.
As far as the graduated ND filter goes, under what types of situations is that good for? I am also curious about how it affects depth of field.
The primary purpose is to darken skies when shooting landscapes. It comes in handy for more than that, but that's the most important use.
Of course, if you're going use graduated filters, then you also must get a matte box. Although someone probably makes them, screw-in grad filters are useless because you can't change the location of the where the grad splits the frame.
How does it affect depth-of-field? Normally not at all, because your exposure is dictated by the clear part of the filter. DoF control is no reason to use a grad.
Ben Longden
Well-known member
The Grad ND is primarily there to tame a wild sky.
Imagine the landscape is perfectly exposed, but the sky is blown completely.. What you ideally want is a filter to reduce the light from the sky to match that off the land... hence the grad.
Dont worry about all the fancy colors - as 1) you will use it once, and 2) you can sort that out in post.
Just think about a .3 and a .6 ND and take it from there. To make the best use of this you WILL need a mattebox so the filter can be slid into the right position.
A clear (insurance filter), a polar and a ND grad is all the glass you need.
Oh,
Cavision, Chrozsiel and a few others make great matteboxes....
Ben
Imagine the landscape is perfectly exposed, but the sky is blown completely.. What you ideally want is a filter to reduce the light from the sky to match that off the land... hence the grad.
Dont worry about all the fancy colors - as 1) you will use it once, and 2) you can sort that out in post.
Just think about a .3 and a .6 ND and take it from there. To make the best use of this you WILL need a mattebox so the filter can be slid into the right position.
A clear (insurance filter), a polar and a ND grad is all the glass you need.
Oh,
Cavision, Chrozsiel and a few others make great matteboxes....
Ben
Well, that is certainly not true. You can't match the proper use of a good grad filter in post -- and there's no rendering needed. I'll also put my Tiffen Soft F/X 2 filter up against anything you want to do in post. You cannot fake the same look.
Flaca Productions
Well-known member
these responses of "fix it in post" are getting a little tired. there was no "electronic means of post production" available for my live shots yesterday. the only way to get rid of all the glare from my background, make the skies really blue and grass extra green was to have a polarizer on. i shoot probably 75% news, and in my world the production stops when it leaves my camera.
hpmoon
PRO user
One thing I've always been confused about (and would appreciate advice on): People always say that you need an ND filter to get a shallower depth-of-field, but what if your camcorder includes aperture priority control? When I set that to the lowest f-stop number possible, isn't an ND filter merely going to make my shutter speed worse?
zac love
Well-known member
I know I'll sound like a snob & old fashioned, but the only priority mode I like in any camera is the "Me" mode. I tell what the camera what to do & not the other way around.
The basic 4 things you have in exposure are: iris, shutter, gain (ISO in still) & ND.
If you want shallow DOF, you have to open you iris as wide as possible.
Now you're left with 3.
Most video cameras have limited gain control. You get 3 presets & if you want to change the intensity you have to go into the menus. Unlike a DSLR where you can change your ISO easily shot by shot, most videographers aren't adjusting their gain unless they need to.
Down to 2.
Adjusting exposure primarily by shutter is going to majorly effect your video. You're going to see crap video if you slow your iris more than 1/frame rate. 1/24 for 24p, 1/60 for 60i. (Some say 1/2xframe rate: 1/48 for 24p).
You also don't want speed up your shutter too much, 1/1000 is going to give you a very strobe like picture. Shoot cars at that shutter speed & their tires sometimes look like they're moving backwards.
Personally when I'm shooting 30p, I stay between 1/30 - 1/120. This gives me some fine control over exposure, but if I need a coarse adjustment I need to venture out of my comfort zone.
Last 1.
This is where ND comes to the rescue. Since I want to keep my iris open, my gain stable & my shutter changes limited, I can use ND to make large steps in exposure.
Make sense?
Back to the OP, I love polarized sunglasses. After my brother left a pair in my car one day, I hate wearing anything else. I have a polarized filter, but rarely do I remember to take advantage of it. Good tool.
To AlexLucas's point, if you're sky is over exposed that detail is lost & you can't fix that in post. Putting in a gradient saves on render time & also keeps the highlights from being lost. More even exposures you can adjust w/ a mask & some filters, but I still prefer to "fix it in post" as little as possible.
Ben Longden
Well-known member
Sure does make sense...
Wish I had written that.
Ben
Wish I had written that.
Ben
hpmoon
PRO user
Thanks for your perspective. I suspect I'm bumping up against the too-fast shutter speed, since my new Sony NEX-VG10 (I created a User Group here) has a large APS-C sensor and I want shallow DOF so have used aperture priority with the lowest f-stop possible, which drives up the shutter speed in bright daylight. At least I think this is how it works, within your explanation. If I were to darken the visible light using an ND filter, having set the aperture as wide open as possible, my shutter speed would take a little more time and let the image "burn" longer. And I suppose I'm best off (consistent with your affection for total manual control) getting one of those rotating variable ND filters so that I can hit my target shutter speed manually for each situation.
Without those strategies, I've simply been getting unacceptable jitters during moderate-speed pans. On the other hand, for the multi-purpose lens I'm using, the minimum f-stop is 3.5, so I'm not sure whether the ND filter will improve things much. I suspect that APS-C sensors in general deal with motion a bit worse than 1/3".
zac love
Well-known member
It isn't the size, but the quality.
If a APS-C sensor can't handle motion as well as a 1/3" it isn't because one is bigger than the other, it is probably because one was made for stills & then hacked for motion as an afterthought (all the current video DSLR cameras fall into this category), while the other chips were designed from the ground up for motion image capture, ie video.
I haven't used the NEX-VG10, but I know it is more of a "consumer" camera, so you're probably not going to have full manual control. If you can control gain, aperture & shutter, go to that mode.
If you can only control one at a time, get a selection of ND filters, like this one:
http://www.bhphotovideo.com/c/product/674665-REG/Tiffen_77NDK3_77mm_Digital_Neutral_Density.html
Though if your results aren't turning out well, I suggest changing to shutter priority. Keep the shutter at "1/frame rate" and you won't have jitters for panning. Use the screw on ND filters & the camera will open up the iris & you'll get some shallower DOF.
Even f3.5 will give you some shallow DOF, not as much as a f1.4 lens, but not the end of the world.
If a APS-C sensor can't handle motion as well as a 1/3" it isn't because one is bigger than the other, it is probably because one was made for stills & then hacked for motion as an afterthought (all the current video DSLR cameras fall into this category), while the other chips were designed from the ground up for motion image capture, ie video.
I haven't used the NEX-VG10, but I know it is more of a "consumer" camera, so you're probably not going to have full manual control. If you can control gain, aperture & shutter, go to that mode.
If you can only control one at a time, get a selection of ND filters, like this one:
http://www.bhphotovideo.com/c/product/674665-REG/Tiffen_77NDK3_77mm_Digital_Neutral_Density.html
Though if your results aren't turning out well, I suggest changing to shutter priority. Keep the shutter at "1/frame rate" and you won't have jitters for panning. Use the screw on ND filters & the camera will open up the iris & you'll get some shallower DOF.
Even f3.5 will give you some shallow DOF, not as much as a f1.4 lens, but not the end of the world.
hpmoon
PRO user
I think it's a little of both. But in any case, I do have full manual control over everything -- even if it's a "consumer" product, it's far from typical in that sense -- and will proceed to try some ND filters after all. I'll not be ruling out staying in aperture priority, though -- it's a tradeoff between staying there for ensured shallow DOF (with a better-looking shutter speed due to an ND filter), and going to shutter priority for ensured smooth motion (with a variably better shallow DOF due to an ND filter).
With regard to the selection of a good ND filter, in contrast to your recommendation of a set of three Tiffen ND filters, I have been hearing great things about this:
http://vimeo.com/groups/nexvg10/videos/12542563
Curiously, though, in order to achieve that variability, isn't it basically two stacked polarizing filters? And would that not make it function as a polarizer two (albeit in competition with itself)?