Are there any advantages/disadvantages in using the built-in ND filter.

Should I always use it when the camera recommends it.

Thanks,

Mark.

Good question.. i've been wondering the same... if this is a post-chip effect surely there is no actual benefit that couldn't be gained in post? What is the difference between this and a negative gain? (I'm a newbie, humour me!)

http://www.digitaljuice.com/djtv/segment_detail.asp?sid=56&sortby=&page=1&kwid=0&show=all_videos

Good video and will probably help answer your question...

ahah. Great answer :)

So I understand that concept using a physical ND filter... I have a more academic question though.. say you did record that very overexposed shot in the video, could you end up with the same DOF shot by applying an ND type filter in post? If the ND filter on the A1 is digital isn't it going to be giving a degradation in quality compared to a real physical filter affecting the actual light hitting the chip in the first place?

the nd filter on the a1 is an actual glass nd filter.
learn how to shoot manual and apply the nd filters when you feel you should.
if auto-nd comes on, your shots can turn out very murky..like at a beach or something.
on auto, the camera has no idea what is sand, sun, water, etc.

the nd filter on the a1 is an actual glass nd filter.

Oh really I didn't realise that at all. I'd presumed it was digital as I thought the switch would have felt more 'mechanical' (I've no idea why now...). Thanks.

Thanks guy's for all the reply's. I was just a little concerned that if I used it I may end up loosing some quality. So am I right in thinking that the filter will help use a wider aperture, and so may give a sharper image.

Thanks,

Mark.

Yes. In ample light situations, using the ND's will provide very sharp shots with even exposure and a greater depth of focus.

You will not lose quality by adding ND's provided that your exposure is what you intend it to be.

Trust your VF over the LCD and don't rely 100% on the meter. I find over exposing my shots by a notch or two gives cleaner shots.

ahah. Great answer :)

So I understand that concept using a physical ND filter... I have a more academic question though.. say you did record that very overexposed shot in the video, could you end up with the same DOF shot by applying an ND type filter in post? If the ND filter on the A1 is digital isn't it going to be giving a degradation in quality compared to a real physical filter affecting the actual light hitting the chip in the first place?

its glass in camera, you can never get the limited depth of field in post that you would shooting with it. I have it on good authority from the engineers that the internal ND on the canons is mated for the design of the chip and in their opinion better than using an external ND filter in its place. Of course an external may be needed as well if its not enough, I also use Circular Polarizers which cut light and glare.

Stephen Eastwood
http://www.StephenEastwood.com

So if one was to use an external ND filter in combination with the internal filters what kind of rating would give a good set of choices?

Not that I have the problem of Hollywood sunshine here in the UK...

If needed to shoot at a slower shutter or wider aperature than its ideal. Also a CP cuts about 1.5 to 2 stops of light if its ok to also cut reflections, sometimes thats intended so a CP would not be usable, but normally thats preferrable to eliminate them in shots of water or through glass.

Stephen Eastwood
http://www.StephenEastwood.com

There are times in bright light when the camera's built-in ND filters aren't enough, and you end up shooting with the lens at the smallest aperture. By adding a screw-on ND, you can open up your aperture more. Most video camera lenses I've been involved with seem to like to be in the mid ranges of aperture, rather than stopped down or opened up all the way.

There is no quality loss with a good quality ND filter.

Steven, if a shot is too overexposed you won't be able to save it in post; though you might be able to get it within the realm of usability, but even then it will look crappy.

i shoot a lot of beach, desert, and tropical content. i've never needed more than the 1/32. i also use a canon polarizer..which provides a bit more ND too.

i wouldn't suggest adding a lower quality ND to that lense. hdv is pretty unforgiving. If you must, buy a highly rated one...and here is some basic info.

Neutral Density filters have four main uses

• To enable slow shutter speeds to be used, especially with high speed films, to record movement in subjects such as waterfalls, clouds, or cars

• To decrease depth of field by allowing wider apertures to be used, which helps separate subjects from their background

• To decrease the effective ISO of high speed film (above ISO 400) and allow it to be used outdoors in bright situations

• To allow cine and video cameras (which have fixed shutter speeds) to film subjects such as snow, sand or other bright scenes which could cause overexposure


Neutral Density factors

• ND.3 (exposure adjustment = 1 stop, reduces ISO 1/2)

• ND.6 (exposure adjustment = 2 stops, reduces ISO 1/4)

• ND.9 (exposure adjustment = 3 stops, reduces ISO 1/8)

• ND 1.8 (exposure adjustment = approx. 6 stops, transmits 1% of light,)

• ND 3.0 (exposure adjustment = 10 stops, transmits 0.1% of light)

• ND 4.0 (exposure adjustment = 13-2/3 stops, transmits 0.01% of light)

• ND 6.0 = (exposure adjustment = approx. 20 stops)

Trust your VF over the LCD and don't rely 100% on the meter. I find over exposing my shots by a notch or two gives cleaner shots.

Are you recommending the VF over the LCD because its not affected by direct sunlight? I've only done about 10 hours shooting with the camera so far but I must admit I rarely find myself using the VF.

the lcd is fine to monitor and focus, but i find the vf to be more accurate with color temp and exposure. the lcd out of the box for me was brighter than the actual exposure..so my initial shots were too dark. also depending on the tilt of the lcd when you are looking at it, it will be brighter or darker
by design. my vf is quite accurate and a huge improvement over other canon cams.

What I don't understand is this...

Why can't we just adjust the shutter speed instead of using an ND filter?

Does a faster shutter speed degrade the video?

In still photography with a digital SLR, all I have to do to get a shallow DOF is to open up the aperture as wide a possible and then use a faster shutter speed to compensate...

thanks...

Yes. In ample light situations, using the ND's will provide very sharp shots with even exposure and a greater depth of focus.

You will not lose quality by adding ND's provided that your exposure is what you intend it to be.

Trust your VF over the LCD and don't rely 100% on the meter. I find over exposing my shots by a notch or two gives cleaner shots.


So is ND best used with a brighter exposure?

So if depth of field isn't an issue, what aperture setting would produce a sharper picture.

Thanks again, its beeen an interesting read.

Mark

David, the comparison of a video to a still camera doesn't hold up in this area. If you use a slower or faster shutter speed, you are going to get an effect. With a slower speed, it will blur and strobe. Faster shutter speeds can affect objects that turn. For example, if you have a fan available, aim the camera at the fan and start adjusting the shutter speed faster. After a time you will see the blades begin to slow, even stop and appear to move backwards. You can, however, use a little faster speed if you want. Some peole think shooting at, say, a 1/100 or 1/125 is better if you are going to do slow motion in post. I've tried that and with interlaced video it may make just a little difference, but not much. With 24P I'm not sure what it would do.

the lcd is fine to monitor and focus, but i find the vf to be more accurate with color temp and exposure.

My A1's VF has a very slight greenish hue, as does a friends A1 as well. Anyone else's have this?

Bill

I went out this evening to shoot some video of the large wind turbines we have around here. Using the 1/32 ND filter gave sharper results and more fluid motion when the blades were turning, I guess this is because of the slower shutter speed. As far as a green tint, I haven't notice this.

Well I'm pleased I asked this question now.

Mark.

David, the comparison of a video to a still camera doesn't hold up in this area. If you use a slower or faster shutter speed, you are going to get an effect. With a slower speed, it will blur and strobe. Faster shutter speeds can affect objects that turn. For example, if you have a fan available, aim the camera at the fan and start adjusting the shutter speed faster. After a time you will see the blades begin to slow, even stop and appear to move backwards. You can, however, use a little faster speed if you want. Some peole think shooting at, say, a 1/100 or 1/125 is better if you are going to do slow motion in post. I've tried that and with interlaced video it may make just a little difference, but not much. With 24P I'm not sure what it would do.


So are there any reasons to change shutter speed based on the motion of what you are filming rather than exposure/light level issues?

Basically no, if you want normal looking video. The purpose of the shutter in motion picture filming is not to adjust exposure time but to create individual frames, basically. That's not really technically accurate but it's the idea. I'm not an engineer so I don't know how it really works, but the shutter "closes" between every frame (does it close and open between every field in interlaced video? I dunno.) In a film camera you have a real shutter that opens and closed; in video it's electronic and I don't know what really happens.

You can often change shutter speed (if you have a camera without clear scan functions) and cause a monitor roll or projector roll to partially go away if you're trying to shoot an old style TV or a movie screen. Different shutter speeds will give different effects. Using a very slow shutter speed can give you a cool effect--try a 1/8 shutter with the camera locked down and people walking by. They'll blur and strobe, but if there's, say, a building in the background, it will stay normal and sharp. If you pan with the people, they'll stay sharp and the building in the background will blur. It's a nice effect for some things. Try zooming in and out with the same setting; you get some cool weirdness there too. You'll have to stop way down and/or use an additional ND filter, most likely.

You can get by with using a slower speed to gain exposure in some circumstances. For instance, a friend of mine and I shot a wedding for a client one time (we normally don't do weddings), and I was using a JVC GY500. He had his Canon XL1, which wanted a lot more light than the JVC. His angle was up in the balcony looking down at the procession coming in. Nobody moves very fast in that situation, so in order to get enough light and not use a high gain, he shot at a 1/30 (standard is 1/60 for NTSC interlace). Since nobody was moving very fast, and since the motion generally was away from the camera rather than laterally across the frame, it all looked normal. But if somebody went running across the frame, he would have strobed.

You can also go slightly faster with your shutter for the opposite, but only a little bit. You go too fast and you get very weird effects, as I mentioned in an earlier post.

So, basically you should use the standard shutter speeds almost all the time--1/48 for shooting 24fps and 1/60 for 60i--unless you're after a certain effect, or in certain limited situations where you can get by with it to control exposure to a limited degree. Most camcorders will show a bit of a quality drop at different shutter speeds. I haven't done anything with the Canon yet, but in shooting slow shutter speeds with a DSR250, the image gets soft and grainy, but you can get by with it because it's an effect and nobody will notice.

The ND filters make a better picture because they allow the iris to be opened half way or so at the sweet spot. That is where the picture looks the best. Sometimes, because I want the f stop at 4.8 and I have 2 ND filters on, I'll use a shutter of 180 to help reduce the afternoon beach brightness and still have 4.8.

Thanks Bill for the info...

That was very helpful...

I'll full around with the shutter speed on my camera to see how it effect the picture...

dave

So it's better for the shutter speed to match the frame rate - is that right?

I mainly use 1080/50i, and have noticed that using a 1/120th shutter speed does give nice results. I film a lot of air shows and have noticed if you run a fast shutter speed you end up having the props on planes look like their standing still. The slower shutter helps keep everything look more natural.

Mark

Just for reference, here's a still frame from a bit of experimentation footage. Mid way through a pan, 1080/50i with the shutter speed at about 1/1000. Pretty extreme, but you get a very definate ghosting in the image. In still shots at this shutter speed, the footage looks very jumpy and neurotic. Could be useful if you want this effect :)

http://pic20.picturetrail.com/VOL91/2062169/11637076/250701321.jpg

I tried using both settings with the ND. On a bright hazy day, like today, it really adds more blue to the sky, and pulls out other colors in general.