Filters and how/when to use them

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Ian Woodward
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Filters and how/when to use them

Post by Ian Woodward »

A couple of easy questions for the video-camera literate on which I’d appreciate clarification.

1. What rules apply when a UV filter has been attached as a permanent fixture to a camcorder lens and, for some shots, one wants to fit, say, a circular polarising filter or a starburst filter or a colour filter? Can the UV filter stay on or does it have to be removed?

2. My camcorder comes with a lens which has a selectable ND filter – that is, Off, 1/6, 1/32. An alert signal on the lens sometimes indicates that an external ND filter is required. The same question applies regarding whether or not the UV filter can remain in situ if such an external ND filter is fitted.

I think it would be of tremendous value and of great interest to the not-too-technically-minded among us, in terms of videography and camera jargon in general, if a long-time expert on the use and misuse of filters could prepare a piece on the subject for FVM because, for me at least, and no doubt for quite a few others, it’s a subject that remains a bit of a mystery and one which, certainly in my case, I’d like to resolve one day.

Ian Woodward
Brian Saberton
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Re: Filters and how/when to use them

Post by Brian Saberton »

Ian. It is perfectly fine to leave your UV filter on the lens when you use a polariser or neutral density filter
Brian Saberton
Ian Woodward
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Re: Filters and how/when to use them

Post by Ian Woodward »

Thank you, Brian, for clarifying this.

I'd still love to see a good feature in FVM about the use of the filter, for those not particularly well versed in the subject.
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leif
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Re: Filters and how/when to use them

Post by leif »

Maybe it should be mentioned, that there is a risk for vignetting wideangle shots, if the filtermounting protrude to much.
Since it is another piece of glass in the light path, there is always a risk for more reflections, impact on sharpness etc.
As always a good sunshade can work miracles.
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Dave Watterson
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Re: Filters and how/when to use them

Post by Dave Watterson »

One pleasure of video is that you can quickly and easily see the effect of filters in different combinations. It was harder when you had to wait for a reel of film to be developed before viewing. Of course that does not help you decide what to buy ... it just means that you can test them when you have them.

Neutral density, polarising and UV should not clash with one another. But keep in mind that it is always worth reducing the number of glass faces between the camera chip and the world outside. I'd take the few seconds needed to remove one filter and replace it with another. After all most people use UV as a protection against damage to the front surface of the lens rather than because they need it. (By the way if you do use a UV filter that way, remember to replace it every year or so otherwise the scratches and marks it accumulates will degrade your pictures.

I see little point in adding colour tinting filters since adjusting colours can be done in the editing stage. You could probably get something which mimics starburst too.

Dave
Ian Woodward
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Re: Filters and how/when to use them

Post by Ian Woodward »

Good point, Leif, regarding the possibility of vignetting on wide-angle shots.

And, Dave, you've raised what I've been pondering on for the past year or so: the fact that most of the effects that on-camera filters achieve can amore or less be approximated in the post-production editing stage.

Starbursts are obviously also possible while editing but, as far as I can tell, not in quite the same way as a starburst filter.

For instance, using such a lens to film a lit-up Christmas tree. Every light on the tree that is in frame should result in a starburst effect, something which I don't think can be achieved in post-production - though it's more than likely that I'm going to be proved wrong here!

You also raised a good point about UV lenses being used principally to protect the expensive camera lens – it had never occurred to me that the UV lens should ideally be changed yearly for the valid reasons stated, but now that you’ve mentioned it…Mmm, I must think about that.

And you've convinced me on one other point which, in my initial query, I really needed clarifying:

Should the UV filter be removed before, say, an additional ND filter is attached?

Yes, it makes sense to do so.

Ian
tom hardwick
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Re: Filters and how/when to use them

Post by tom hardwick »

Ian, I've written many words on the use of filters fitted to camcorders in Positive Image over the years. In a nutshell - Don't. That is, don't use filters unless you really, really have to. You certainly don't need a UV unless you're filming on wind-swept beaches, and the only filter that cannot be successfully replicated in post is the polarisor, so I'll let you use that one.

This DON'T applies to cameras that use small chips, and the smaller the chips, the louder I yell DON'T. It's all to do with focal lengths and dof.

The star burst - like the soft focus - is a screen and not a filter (as it doesn't filter anything), so my recommendation still holds. And do remember the truth that filters add nothing - they only take away.

Much better to shorten the shutter speed to 1/100th than to fit an external ND, believe me. Far too many NDs, UVs and polarisors are uncoated for my liking.

Every filter you fit increases the flare levels and reduces your lens hood's efficiency. Multi-coatings are really tough these days so don't be afraid to clean your front element. My specs are Zeiss T* multi-coated and I've cleaned them every day for years using crushed Canadian Redwoods (kitchen roll) with not the slightest damage to the coating.

tom.
ned c
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Re: Filters and how/when to use them

Post by ned c »

I agree with Tom that any glass in front of the lens should be a high quality optical glass, coated filter; however, I always have a protective filter in position and it has from time to time recieved flecks of flying mud, etc which would certainly have damaged the coating on the front element of the camera lens. I also use effects filters occasionally; it's fun and much quicker than rendering some effects in post.

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Ian Woodward
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Re: Filters and how/when to use them

Post by Ian Woodward »

You’ve certainly given “filter-or-no-filter?” doubters like me, Tom, much uncomfortable food for thought!

You have also seem to have gone against the Holy Grail of all still-camera/camcorder advice columns in saying “DON’T use a UV filter” which, as you say, most of us use purely as a projective membrane between the outside world of in-the-field use and the inside world of the camera lens it is, hopefully, protecting.

I really can’t make up my mind about this because it was the one thing that used to give me (and possibly many others) a certain degree of comfort when filming out and about in the vagaries of Britain’s island weather.

The experience you bring to your answer in this forum thread convinces me, yet again, that the whole issue of what and what not to screw onto the end of a camera lens would make a fascinating piece.

Could FVM perhaps be persuaded to reprint your article, Tom, in another part of the magazine, with the sort of add-on info that you’ve written in this thread. Your chosen lens cleaner, for instance, is informative in itself. I just use the soft, washable lens-cleaning cloth that came with the camera. Should it be otherwise?

Thanks, Ned, for your thoughts.

The big debate now, it seems, is:

Is the UV filter a good idea or just pie in the sky?

Ian
Geoff Addis
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Re: Filters and how/when to use them

Post by Geoff Addis »

I can only echo Tom's advice. Try this as a test, point your camera outdoors throughthe window with the window providing a dark frame, do this with and without filters whilst gently moving the camera around a little and see the effect of internal reflections on the image, even with the best filters.
tom hardwick
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Re: Filters and how/when to use them

Post by tom hardwick »

Ian, I can't say this with more force but I'll say it again - don't use filters unless you absolutely have to.

For years I've used matching cameras in my work. I had two VX20000s, then an FX1 and a Z1. I could demonstrate to anyone, in a matter of seconds, the image degradation that comes free when you simply add a UV filter. Having seen my shots you'll happily go down to the lake and skim your UVs out over the water, happy in the knowledge that it bounced 15 times and that your images will now be as clean as they can possibly be.

It's all down to focal lengths Ian. When you're filming with 1"/3 chips you can be shooting at 3.5mm. The same angle of view on a still camera is 30mm - a far longer focal length, and as such dof issues wont bring the inevitable imperfections (two extra air-to-glass surfaces) into sharp relief.

By all means use 'protective' UVs on 35mm cameras, but again I ask why? I'm adamant, and have said it till I'm Avatar blue, don't use filters. I don't, and I use my cameras a lot - a LOT.

Now then, you've bought a Canon camera with a 12 x zoom lens (I'm guessing here). This lens most probably has 15 individual elements in the line-up, with two of them aspherical. All of these elements will be multi coated, and *the* most important element (from a coating point of view) is the front one. It's the best lens Canon can give you at the price. If they thought that adding a £15 UV would improve the performance, they'd have included one.

There's more on this if you still want convincing, but I don't want to bore everyone rigid.

tom.
Ian Woodward
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Re: Filters and how/when to use them

Post by Ian Woodward »

Tom, you’ve finally convinced me – stay clear of filters.

I’ve had several Canon camcorders over the years: my current ones are an XL2 (22x zoom,) and a Legria HV40 (10x zoom).

I must confess that about a year ago I noticed that (re the XL2) that images of, say, corn blowing in the wind or leaves on trees fluttering in the wind, when using AF, were not properly in focus. These are just a couple of examples but there are countless others like it.

Prior to a year ago, everything was fine and pin-sharp. But it’s only now, following the warnings about filters, that something’s suddenly occurred to me – because the focusing being compromised started at precisely the time I fitted a UV filter to the 72mm lens.

It was one of a set of three I bought from Canon, the other two being an ND8 filter and a circular PL filter. I’ve just removed it from the camera and put it back in its case, alongside the other two.

And, Geoff, I’d already noticed internal reflections on some images. Thanks for alerting me to the significance of this error.

PS: Tom, I don’t know about boring “everyone rigid”, but I, for one, am never bored by reading advice given to someone else with less knowledge than the person giving it. I welcome seeing such advice.

Ian
Roy1
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Re: Filters and how/when to use them

Post by Roy1 »

Tom. I have just bought filters and a wide angle lens attachment for a Sony HDV camcorder. I thought they would be handy in Spanish sunshine and the Extra wide angle for use in confined spaces. They cost me well over £100 and apparantly have a good reputation, but your advice has made me seriously think of not using them although I think content is more important than a slight reduction in quality. However if I find on a test that I get the side effects that have been mentioned I will certainly not use them. Thanks for the enlightenment.
tom hardwick
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Re: Filters and how/when to use them

Post by tom hardwick »

I don't know a single camcorder that wouldn't benefit from a wide-angle converter. The Panasonic 151 has a much toted '28mm' wide end, but although that sort of focal length used to look wide in 1976, it's pretty tame now.

You don't say what HDV camera you've got Roy, but any camera that doesn't have switchable NDs on the body has them automatically activated internally - you're just not told about it, that's all. So 'filters for the Spanish sunshine'? What are those?

If you do use a filter then it's always best to remove it when you fit the wide-angle converter, as the reduction in focal length always exacerbates the flare problems.

tom.
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leif
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Re: Filters and how/when to use them

Post by leif »

With my present camcorder (Panasonic NV-GS400 SD) I have observed that if I keep the filter on the camcorder when mounting the wide-angle lens, it will cut the corners at widest settings.
Unfortunately the problem doesn't appear on the lcd-monitor - it is appearently not showing the full frame. So I must remeber: full wide and a small step backwards.
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