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Canon XH Series HDV Camcorders
Canon XH G1S / G1 (with SDI), Canon XH A1S / A1 (without SDI).


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Old June 13th, 2008, 08:32 PM   #1
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Shooting racing as day decends to night.

Each Saturday I shoot the action at a local short track and so far almost everything has gone great using the A1. Almost. I shoot all manual and have no problems in full sun when the races start and under the lights when they end. The trouble comes in the tween time when the front stretch and turn 1 are shaded and the rest of the track is in sunlight.

As expected, I'm always moving the camera and zooming to follow the action. Since the lens ring controls are servo and allow only one change at a time, manual iris changes are hard.

Should I try letting the iris work automatically to handle the changes in light or should I live with the light changes as the cars move into the shadows? I'd like to try it, but I'd hate to really blow the shots since I can't really go back and ask them to run the race again since I messed up.

Any thoughts would be appreciated.
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Old June 13th, 2008, 09:22 PM   #2
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Hi Tripp. I thought you should be able to zoom with the rocker controls and adjust the iris wheel at the same time. Are you saying that it doesn't work?

Richard
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Old June 13th, 2008, 09:47 PM   #3
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Quote:
Originally Posted by Tripp Woelfel View Post
...turn 1 are shaded and the rest of the track is in sunlight.

...Since the lens ring controls are servo and allow only one change at a time, manual iris changes are hard.

Should I try letting the iris work automatically to handle the changes in light or should I live with the light changes as the cars move into the shadows? I'd like to try it, but I'd hate to really blow the shots since I can't really go back and ask them to run the race again since I messed up.
I've been having similar issues recently as well, but my pains have been due to windy days with clouds constantly messing with my exposure. I've been trying to do what you're doing (manage things manually), but I'm messing up some shots. I work with an entirely different camera than you, but here's what I've been doing lately with pretty good results...

By looking at my LCD viewfinder image, histogram, and zebras, I know roughly how I like my exposure to look. So, I turned on auto-exposure (on a cloudy, windy day) and watched how it responded to the exposure changes. It was very close to what I like, but not quite close enough. So I went into a setting on my camera that allows me to tell it how much offset/shift (up or down) to apply to what auto-exposure selects, and I set mine to -2. Now when auto-exposure is running, it applies that adjustment and my exposures are pretty well maintained throughout exposure changes.

The thing you have to remember though, is that auto-exposure [I believe] works off of certain areas of your composition. On my camera, I can't select what that area is, but I know roughly what it is through various tests. Having said that, if you would go this route, you'd need to know where that area is otherwise your auto-exposure could be exposing for the wrong portion of your composition (and mess up your shot[s]).

Overall my #1 piece of advice is to test any modifications to what you're currently doing before you go out and do it. I too would hate to hear you blew shots by trying this for the first time at the event.

Hope some of this helps a little,
Andrew
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Old June 13th, 2008, 10:47 PM   #4
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Hi Trip...................

It took only 3 minutes testing to discover the error in your assumption with this.

The Zoom ring takes precedence over the Focus ring.

If attempting to do both at once, only the Zoom activates.

If you're Focusing and touch the Zoom ring, it immediately reverts to Zoom.

The Iris ring is NOT linked to either. You can manually change the Iris no matter which of the others is being used.

That said, you seem to be making life immensly difficult for yourself.

Sort of similar to what Andrew was saying.

Set the operating mode to T.

Nail your shutter to 1/120 or whatever floats you're boat.

Get to know what area of the screen is particularly senstive to what lighting conditions and apply the appropriate amount of AE shift (via menu) to get the look you want.

This will require you doing some test runs but will be worth it in the long run.

The AE system is pretty darn quick and will keep track better under the conditions you described than you will.

Things that can cause anomolies are, as you'd guess, an area or areas of relatively intense light against hard shadow, it can switch quite harshly very suddenly with a relatively small change in percentage area of the frame.

Spotlight mode may well be able to offer some better degree of control under these conditions but something I've never played with, so shall leave to others for comment.


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Old June 13th, 2008, 11:21 PM   #5
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Great info all...

Andrew... I'm going to have to dig into the manual and find out how to configure AE to my needs. It may not get there to what I want but it's got to be closer to what I want than what I can do manually.

It all happens so fast on the track that you have to track the cars, zoom as they move, watch past the LCD to look where you want to move next. If the camera can handle the iris for me it would be great.

Chris... Thanks for breaking that down. I should have been able to suss that out myself but that just shows you what a pillock I am. Your insight and experience are especially enlightening.

I guess the good news is that there really won't be areas of both light and dark in the same shot. As I pan the track, I move from lateral sunlight to deep shade as the cars move into the shadows of the grandstand on the SW side of the track. So there might not be too much to trip up the A1's electronic brain.

Sounds like you both are saying that the camera can handle the work, which would free me to chase the cars. You're both absolutely right that testing is essential, but replicating the conditions of the race track are not exactly possible, so I'll play around with what I have to work with tomorrow morning before I go to shoot tomorrow night. I'm hoping that it's cloudy tomorrow.

Thanks again.
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Old June 13th, 2008, 11:57 PM   #6
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Hey Tripp.................

Just a bit more explanation about the AE Shift thing.

Whenever I do what I was describing to you, I find the AE system (set at 0) consistantly overexposing, giving blown out highlights and a distinct lack of colour depth.

I usually set the AE Shift to anywhere from -.5 to as far down as -2.0, dependant on the subject.

Again, why a bit of experimentation goes a long way.

Keep us posted, shall be interested in how it works out.


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Old June 15th, 2008, 04:55 PM   #7
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I've got everything I need... almost

To quote the Blues Brothers.... Although it was overcast yesterday, and the differences between the light and dark areas of the track were less pronounced than if the sun was out, I relied upon AE for the middle races as there were shadowed areas. Here's what I found.

- On anything other than very close up shots, it worked fine. You could see the effect of the iris. They were positive and definitive with no apparent hunting or lag. Absolutely better than what I could have done.

- On very close up shots on the front stretch (close to me), the iris changes were notchy and made for changes in a stair step pattern that were big enough to be objectionable to me. Again they were definitive and it didn't wander around. With no previous experience using AE (I normally shoot all manual), I'm going to guess that either the amount of zoom (about 8/10 of max) could effect it, (less likely) or the fact that the background and track are moving by the lens so fast, as the cars run over 100 MPH. The varying lightness of the background may be confusing it somewhat. (more likely, it would seem)

My guess is that the light level sensor samples what's coming through the lens over a small fraction of time, then makes a decision on where to set it. This cycle then repeats over an over. The speed of the background, even with little light changes might cause the electronics to have to think harder to get the right answer.

I didn't have time to consult the manual about the setting in the menu where you adjust the AE threshold, but I'm going to to see if that might smooth things out.

Also, it seems that the focus ring and my VariZoom LANC controller do fight for function control, with zoom winning. I'll have to experiment a bit more but moving the rocker on the controller does seem to wrest the control from the zoom ring. Kinda of a pain, but I can work around that.
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Old June 16th, 2008, 12:51 AM   #8
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Thanks for getting back, Tripp...........

Just as an experiment, to see if it in any way helps with the issues you found, you might want to try, er, dare I say it..............full Auto (exposure)!

OK, ok, I know, asking for trouble etc, BUT, I haven't analysed the steps available to the camera when in that mode, and you may well find that the algorithm used in Auto is actually quite clever at working out which is the "least worst" bet during the sudden changes you were seeing under certain circumstances.

The worst that can happen is you have one segment of completely unusable video. The best is far smoother transitions from one scenario to another.

Just a thought, heck, I let my Nikon D80 do most of the thinking most of the time, I simply don't have time to do the math with my style of still photography. It usually does better than I would have (er, usually, every once in a while it pulls a complete dogs dinner out of the hat).

Can't say I really got a grip on the problems with regard to the Lanc controller - would you mind running that by us again?


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Old June 16th, 2008, 07:06 AM   #9
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Chris... I hadn't thought of going full auto. It's worth a shot. There's no doubt that the algorithms used to make this work are sophisticated and designed to take in a variety of shooting situations. It's also going to react a lot faster than my old brain. The only advantage we humans have is experience and the ability to anticipate what we expect to happen to our shot next. And we know that doesn't always work out.

On the LANC deal... it seems that the LANC zoom and focus controls are on the same "interface" as the zoom and focus rings on the lens. By that I mean it doesn't seem that you can zoom using the LANC and adjust the focus rings at the same time. In following cars on the track, I would zoom using the external controller while focusing simultaneously. When doing this, the zoom bar on the LCD would show the zoom change but the focus distance display would disappear. Once finished zooming, the focus distance display would reappear with the same value (ex.: 423 Ft) as it had before I started twisting the focus ring.

I haven't tried zooming with the ring and focusing with the controller as the Varizoom focus control is so imprecise as to be useless. (I think that's more due to the way the Canon works than Varizoom's implementation.)

This leads me to believe that the on-camera zoom rocker has its own exclusive path to the zoom control that is unaffected by the user manipulation of the lens ring controls. More testing is required, but even if that's the case it won't really help me as it's impractical for me to use the on-camera zoom rocker simultaneously with the wild panning and tilting needed to cover the on-track action.

I hope that clears things up a bit. BTW... Thanks for your help with all this.
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Old June 16th, 2008, 07:51 AM   #10
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From my observations, the XH-A1 auto-exposure appears to work like this, shooting 1080/50i, with AGC switched off:
- If it can, it keeps shutter at 1/50 (1/60 on NTSC versions?) and apperture wider than f8;
- When the scene become too bright for 1/50 + f8, it speeds up the shutter;
- If the scene is too dark for 1/50 and maximum apperture, AE lets the scene stay dark. I guess that if you have AGC switched on, it will add gain. I have found that it doesn't slow the shutter below 1/50. Maybe it would if you are using 25F or 30F?

To make the best of AE, I'd choose the ND setting that gives you just enough light in the darkest part of the track.

When you are panning with the cars, using 1/60 will give a more blurred background than, say, 1/120. This may or may not be to your liking.

To overcome the zoom/focus problems, have you tried using auto-focus? I find it is rather more reliable than I am when tracking moving objects, though my subjects seldom do more than about 70 mph, not 100+ (I shoot a lot of steam trains).

Regarding the too-noticable exposure changes: have you investigated the "shockless" transition option in the XH-A1 menus? The manual doesn't explain what it does, but it seems to me that it fades the apperture changes over a second or so, rather than making them instant. Can anyone else comment on this?
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Old June 16th, 2008, 02:00 PM   #11
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Focus & Zoom...........

Ah, I see what you mean.

Going back to my first post, I actally plonked the camera down on my study desk and had a fiddle with the zoom, focus and apeture controls.

I think every one is aware that the A1 has only one servo to serve both Focus and Zoom. It can't do both at the same time.

What I had not appreciated till I did the test was that Zoom overides Focus at all times.

Ergo, if you are moving the Focus ring (or using focus on a Lanc) the merest touch on the Zoom ring (or zoom rocker on the Lanc) will kill the focus and instantly revert to Zoom mode (hence why the distance reading for the focus disapears from the finder).

As I mentioned in that post, neither has any bearing on the apeture ring which "does it's own thing" whatever else is going on.

Quite where all this leaves you when trying to keep close framed on a fast moving target which is rapidly going out of focus, I'm not quite sure.

A bit early in the morning to get my head around that one - I'll go have another cup of coffee and get back to you...........


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Old June 16th, 2008, 05:11 PM   #12
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OK, coffee had, brain (or what passes) functional.......

Take one rock solid rule with these lenses:

Zoom in to Z99. Focus. Zoom out to frame. Shoot.

Nowhere does it say "re - focus".

That's because if it's focussed @ Z99 say, at 500 yards, everything in the finder between Z99 and Z0 (and the camera position and 500 yards) will, by definition, be in focus.

So, take your race meeting.

If you zoom to Z99 and focus on the FURTHEST part of the track where a target is likely to get to, turn off Auto Focus and zoom out to frame the point of nearest approach to the camera, it should, in theory, be in focus.

So, if you use only the zoom to track your targets and ensure that by the time you have got to Z99 you're framing the furthest distance (500 yards) first focussed on, it's all going to be in focus.

This is where experience and practice come in. You'll need to be able to ensure that the distance framed is appropriate for the zoom setting applied.

If you get to Z99 and the lens is still only pointing at something 400 or 450 yards away, it will be out of focus.

Once mastered you should be able to switch off Auto Focus and put some tape across that IAF button.

It's a great theory, I wonder if anybody has mastered it?

Can anyone see a flaw with the theory?


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Old June 16th, 2008, 07:22 PM   #13
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Quote:
Originally Posted by Mark Fry View Post
To make the best of AE, I'd choose the ND setting that gives you just enough light in the darkest part of the track.When you are panning with the cars, using 1/60 will give a more blurred background than, say, 1/120. This may or may not be to your liking.
Good thoughts but I like to shoot racing with a really fast shutter. I'll keep it at 1/500 as long as I can because of the clarity and for some shots, DOF. You can see examples of some ground level shots here: www.vimeo.com/oxfordplains

In full sunlight I can keep the iris near 4 which works well.

Quote:
Originally Posted by Mark Fry View Post
To overcome the zoom/focus problems, have you tried using auto-focus? I find it is rather more reliable than I am when tracking moving objects, though my subjects seldom do more than about 70 mph, not 100+ (I shoot a lot of steam trains).
Good idea. I'll try that out before the next race and see how it works.

Quote:
Originally Posted by Mark Fry View Post
Regarding the too-noticable exposure changes: have you investigated the "shockless" transition option in the XH-A1 menus? The manual doesn't explain what it does, but it seems to me that it fades the apperture changes over a second or so, rather than making them instant. Can anyone else comment on this?
I was wondering what that meant. I'll have to play with that one too but it might be a little spiky as there's virtually no time between races to test before taping. I might just change the setting before the event and see how it works. Can't be much worse.

Thanks for the help Mark.
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Old June 16th, 2008, 07:44 PM   #14
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Focus is actually the least critical element in this triad, but this is good information for me being a perfectionist.

I wasn't aware of this rock solid rule. Without classical training, what I've learned has been picked up along the way. Kinda like Harpo Marx and the piano, if I can indulge the comparison. Given the fast action, I'm forced to periodically re-focus.
Here's my setup:
- Zoom to z99 to a point midway between my nearest and farthest points of focus ~400 feet, and focus
- Lock that setting into the focus preset
- When I'm done making any manual focus changes, I just hit the focus preset and I'm ready

Using this procedure, I find that I will be slightly soft when I zoom in fairly tightly on the nearest part of the track(~140 feet), which if I'm reading what you wrote correctly, is to be expected. Or is it. Perhaps it's because I've finished my first ale, but I'm not sure I'm grasping the whole concept of the theory.

Clearly Harpo fared better from being self taught than I.
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Old June 16th, 2008, 08:44 PM   #15
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I think the theory is correct...

Tho' on reflection I think I may have slightly "mispoken" with regards to it's effects.

Lets go back to your race meeting.

I "think" you said the furthest (action) distance from the camera is 400 feet.

Let's say it is.

If you zoom to Z99 on that point, 400 feet away, and focus tack sharp on an object there, due to depth of field, a zone something like from 380 feet out to 430 feet out (this is a wild guess) will also be "in focus" (it won't be tack sharp but acceptable).

As you zoom back from Z99, the increase in depth of field means that the 380 (closest "in focus" point) rapidly works back to say (guess) 50 feet @ Z0 (maybe even less) and the furthest "in focus" point is now say, 700 plus feet.

So, if you pick up a car @ 50 feet @ Z0 and lock it into the centre of the screen , then track it, zooming in to keep it as large as possible, then if arriving at Z99 coincides with arriving at the intial 400 feet, it will always be in focus!

This explains why, if have initially Z99 focussed at 400 feet, and approach Z99 @ 350 feet, it will rapidly go out of focus, as @ Z99 the closest point of "in focus" is 380 feet.

I realise there is a distinct whiff of "how many angels can dance on the head of a pin" here, but if the lens won't focus and zoom at the same time, it appears the only useable tracking method available.

Stand by for the stampede of wildlife and action videographers when the new twin servo Canon lenses land. That's gonna be something to watch.


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