ND Filters

[stingman]

I havn`t seen ND filters discussed on here. So here goes...

Over on the IAC Newsgroup, they are discussing ND filters.

They are saying that if you switch in your ND filter then you lose a bit of quality. This shows up more on HD stuff.

I used my friends Sony FX1 and in the viewfinder, it shows when to use 1,2 or 3 number ND filter?

If I remember correctly, my old Panasonic videocamera (seperate from the video recorder, joined by a cable) had this filter. I didn`t know what it did but it certainly cut out the light!

Does it effect HD stuff?

Your views and experiments are most welcome.

[Michael Slowe]

Ian, that must be rubbish! All the filter does is reduce the light coming in so you can open up the iris and control the exposure, they are used universally in all photography. I have never noticed any picture degradation in HD, indeed it generally improves it because you are using the best section of the aperture range.

[stingman]

What they may be getting at is that when you pass an through a piece of plastic or coating then this will degrade it. You may notice it in HD because the definition is much better. Coatings and such are made up of fine particals.
To get a pure, clean picture, the image should pass through the lens that is perfectly clean.
You are passing the image through a physical object.

Is this wrong?

I do accept your comments that are proberly right!
My comments here are just speculative and i`m just throwing options and thoughts into the subject.

[ned c]

ND filters make no difference to the color balance of a picture.

Filters come in various qualities, optical glass, coated optical glass, gelatin and resin. The best are said to be the coated optical glass, they are expensive. I use both coated optical glass and resin. On the IAC members forum there has been considerable discussion about the effect of filters on picture, mainly about the immense depth of field of small CCDs and the likelihood that even a small speck of dust will either be in focus or sllightly oof and affect the image by scattering light.

Also the fact that uncoated filters may cause degradation by flare, ie scattering the light. This is true but I use carefully cleaned filters for special effects in camera and frankly have no problems with both SD and HDV.

It is true that at very small apertures eg at f16 the opening is so small that the light is scattered and degrades the image. Most lenses have a "best area" often around f4.5 to f6.3 and we use ND filters to get the aperture into this area as unlike still photographers there are problems with just adjusting the shutter speed.

Hope this helps

Ned

[billyfromConsett]

I've got a Sony VX2100 that has 2 ND filters. I use it when the camera decides I need to use it, and also to get the iris wide open so I can do cool focus pulls.

[tom hardwick]

Ian - the IAC newsgroup said nothing of the sort. Internal ND filtration is the way to go, and external filtration is what opens up the can of worms and leads to image degration.

tom.

[stingman]

I stand corrected Tom.
Thank you for pointing out my minor error

I didn`t really know if they were internal, external or if you could stick them up your jacksy. I just wanted to know what they were used for as and because of being a filter it would degrade the picture, nore noticable on HD.

[tom hardwick]

Anything you do on the timeline (except for straight cuts) degrades the picture, so we shouldn't get too worked up about this. If you improve the colour balance, change the exposure, put into slow motion, grad filter the sky, crop, add transitions and fades and so on - these can all hugely improve the overall film at the expense of outright 'quality'.

But we all know the overall quality of a film certainly isn't measured in lines per millimetre.

tom.

[stingman]

You are of course right Tom. ANYTHING we change in the timeline WILL degrade the picture. It normally takes the form of grain.

[Dave Watterson]

Perhaps a more interesting issue is whether we should put any filters in front of a video camera lens at all.

It used to be standard advice that having a skylight/UV filter would protect your precious lens and could be cleaned more easily than the len. The amazing depth of field on modern camcorders, however, means specks of dust on such a filter may be revealed. Marks on the skylight filter would degrade the image noticeably.

I guess that also means the old 35mm still camera trick of taking pictures right up against the cage of an animal in the zoo often meant the wires or bars disappeared because they were completely out of focus.

In one of his FVM articles Tom Hardwick wrote about his meticulous cleaning operation before he sets off on a wedding video shoot. Perhaps we should all be as "house proud" of our gear.

Dave

[tom hardwick]

Spot on Dave. I don't recommend using filters of any kind on camcorders for the very reasons you state ~ they more often than not degrade the footage, reduce the hood's effectiveness and can often be applied (and more importantly un-applied) in post.

tom.

[stingman]

Perhaps a more interesting issue is whether we should put any filters in front of a video camera lens at all.

Dave

I think that I would never use a filter in my film-making. As discussed earlier in this thread.
I may if I had top of the range gear and cleaned everything everytime that I use it.

How many of us clean the videocamera lens everytime we use it?

Not me! Sorry.

[tom hardwick]

Don't feel sorry Ian. You have to be very careful when cleaning your lenses and I'd not advocate you doing it before every shoot unless of course it was obvious that it needed doing.

Last month the groom shook the Champagne bottle with his thumb over the end, and that squirted straight out, splodging all over my wide-angle converter. Luckily I could quickly remove the lens and carry on shooting the toasts. I've left the shot in the edit as I reckon it looks good.

Same too with the head cleaner. Use sparingly, and only when needed.

tom.

[stingman]

Good advice Tom.
I find my sleeve is a good way to clean my lens I have to make sure it`s clean through because if I forgot my hanky then the sleeve is always their to get me out of trouble

[alansmith]

Hi, I use a wide angle converter on my XM2 most of the time, I cannot fit a filter even if I want one, due to the lack of screw thread and the special wide angle lens hood. I, like Tom, always clean the lens with a decent lens cleaning cloth before and numerous times during shooting. I still get the occasional particle and have to be aware at all times. The XM2 has internal ND filter and does help to keep the aperture open.
Alan