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Old February 26th, 2010, 07:46 AM   #1
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Focusing while zooming a GY-HM700

I have been using a Sony DSR-PD170P to film fast moving vehicles and I was hoping to make the move to HD. I would love an EX1R but I am worried about rolling shutter. The GY-HM700 is looking almost perfect but I am worried about being able to focus while tracking the subject.

I would really appreciate some feedback from GY-HM700 users about this.

I this is an example of the type of filming I do.


Do people think rolling shutter skew would be a problem if I did this with a CMOS camera?

p.s. colour correction and smooth panning are other things I hope to improve
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Old February 26th, 2010, 09:33 AM   #2
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In a word - yes!
I think it would be a problem, I've seen massive skew on long lenses with birds flying for instance, but I know there are many others who never seem to see it. You'll have t test them for yourself.
It stands to reason though, the CMOS cameras of the same spec cost a fraction of the CCD ones - why? Because they have issues (more severe than those that CCDs have).
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Old February 26th, 2010, 04:14 PM   #3
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Laurence, focusing while zooming simply takes practice practice and more practice until it is second nature.
I used to do robotic cameras at NASCAR races and getting the feel of following a car at 190 mph, while zooming whether in or out and keeping it framed and focused took practice so while they cars were running but we weren't on the air I and other operators would practice. Follow the car, zoom, keep in frame and focus. Do it again and again and again. Then it becomes natural. Once you get used to it it's not hard and of course it always help to have the lens backfocused properly so you've got some leeway in your focus.
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Old February 26th, 2010, 10:39 PM   #4
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I note that you seem to be using a fast shutter of about 1/150th sec. or thereabouts, maybe I am dreaming.

A CMOS cam's artifacts will be more evident if you want a faster shutter speed which is a dynamic style thing for the sort of events you do. You would probably be forced to use 1/50th sec or even "shutter off" to mask the rolling shutter artifacts in motion blur.

That said, the original EX1 and EX3 were not anywhere near as bad as I imagined they would be.

Why not rent the EX1R and JVC for a test or see if the dealers will let you try a demo camera at your next meeting.


PS. Were you using a 35mm groundglass adaptor and long lenses when you shot the clip?

Last edited by Bob Hart; February 26th, 2010 at 10:42 PM. Reason: error
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Old February 27th, 2010, 06:26 PM   #5
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It's just a matter of practice really. :)

I film football (soccer) matches, and they are completely fluid as far as movment is concerned. Because of this it's one area that a 1/3" chip, to me, has an advantage over a 1/2" chip, the greater depth of field means you have a wider latitude in keeping things in focus whilst zooming in and out. As for CMOS vs CCD, I was lucky enough to not get any noticable effect using the camera I had before I got the HM700, so while I won't say it's nothing to worry about I don't think it's as bad as some make it out to be if you control the camera sympathetically.

Still, as Bob said, try both out if you can rent them, that way you'll be able to get a better idea for yourself.

Have Fun,
Jim.
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Old February 27th, 2010, 07:09 PM   #6
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Quote:
Originally Posted by Bob Hart View Post
Why not rent the EX1R and JVC for a test or see if the dealers will let you try a demo camera at your next meeting.
Quote:
Originally Posted by James McBoyle View Post
Still, as Bob said, try both out if you can rent them, that way you'll be able to get a better idea for yourself.
Quote:
Originally Posted by Steve Phillipps View Post
You'll have t test them for yourself.
Hehe, I am getting the message... I guess the main thing is that I don't want to write off the JVC simply because of my lack of experience as a camera operator.
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Old February 27th, 2010, 07:27 PM   #7
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nor should you wirte it off due to lack of experience. Practice even off the track, follow cars on the street, dogs running etc. Learn where to focus to gain the most DoF, remember DoF can work both ways.
As an example, at many of the tracks I ran camera at, the camera position I ran, had cars coming to me. I would focus at the far end of the track and allow my DoF to cover me as the cars came towards me. Keep in mind these were 2/3 inch chips with lens that cost more than many new cars at the dealer AND when we built the units the video truck checked our backfocus (we did also but the had better monitors) and the backfocus is key. There really just isn't time to play around with focus when you'r trying to pick out a certain car that's coming to you at 190mph and the director is "talking" to you thru the headset. You've got to pick it up, frame it and follow it until he calls for the next shot. No time to focus, it's got to be right coming out of the corner.
Practice, check BF, check what you get for DoF forward and back at different f/stops, kearn the camera llike the back of your hand and you should be fine.
BTW, I know a guy that does motocross with a JVC HD100 and the Fuji16X lense. IT's a sharp as a tack so it can be done and done well.
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Old February 27th, 2010, 07:47 PM   #8
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CMOS vs CCD

Quote:
Originally Posted by James McBoyle View Post
As for CMOS vs CCD, I was lucky enough to not get any noticable effect using the camera I had before I got the HM700, so while I won't say it's nothing to worry about I don't think it's as bad as some make it out to be if you control the camera sympathetically.
Hmmm, I wonder how sympathetic I am!? When you filmed football matches with your old camera did you ever stand near the sideline and follow the ball as it passed you?
I would imagine that sort of rapid pan would be similar to what I want to do.

Quote:
Originally Posted by Bob Hart View Post
A CMOS cam's artifacts will be more evident if you want a faster shutter speed which is a dynamic style thing for the sort of events you do. You would probably be forced to use 1/50th sec or even "shutter off" to mask the rolling shutter artifacts in motion blur.

That said, the original EX1 and EX3 were not anywhere near as bad as I imagined they would be.
Hmmm, while the fast shutter speed is not really that important for anything more than a cool effect I would like to have the option if possible... but thanks for the suggestion. I will make sure to try both slow and fast shutter speeds when I test out the cameras.

Quote:
Originally Posted by Steve Phillipps View Post
In a word - yes!
I think it would be a problem, I've seen massive skew on long lenses with birds flying for instance, but I know there are many others who never seem to see it. You'll have t test them for yourself.
It stands to reason though, the CMOS cameras of the same spec cost a fraction of the CCD ones - why? Because they have issues (more severe than those that CCDs have).
Steve
I would love to see some of that footage Steve! Long lens pans of flying birds are really similar to what I want to film. I read a thread on here about that and it deteriorated into an inconclusive bloodbath of documentary filmmakers!

You also hit the nail on the head regarding cost. I would just buy a Sony HXC-100 if I had the money!
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Old February 27th, 2010, 09:09 PM   #9
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Focus

Let me start by saying thankyou all for taking the time to respond, I am actually working this weekend (at the moment in fact) so I apologize for the delay in my responses.

Quote:
Originally Posted by James McBoyle View Post
It's just a matter of practice really. :)

I film football (soccer) matches, and they are completely fluid as far as movment is concerned. Because of this it's one area that a 1/3" chip, to me, has an advantage over a 1/2" chip, the greater depth of field means you have a wider latitude in keeping things in focus whilst zooming in and out.
I hadn't thought of that benefit of the smaller sensor. I sometimes I film in low light so the larger sensor did appeal but after some trouble with the local authorities I might not be doing that much any more. --> YouTube - Osaka Touge Drift HQ

If you film a cross pass in front of you how do you physically do it.

Do you use the zoom rocker and focus using the ring?
Do you adjust both the zoom and focus rings with one hand?
Do you have a Zoom Control Unit on the handle of your tripod?

Quote:
Originally Posted by Don Bloom View Post
Laurence, focusing while zooming simply takes practice practice and more practice until it is second nature.
I used to do robotic cameras at NASCAR races and getting the feel of following a car at 190 mph, while zooming whether in or out and keeping it framed and focused took practice so while they cars were running but we weren't on the air I and other operators would practice. Follow the car, zoom, keep in frame and focus. Do it again and again and again. Then it becomes natural. Once you get used to it it's not hard and of course it always help to have the lens backfocused properly so you've got some leeway in your focus.
Quote:
Originally Posted by Don Bloom View Post
nor should you wirte it off due to lack of experience. Practice even off the track, follow cars on the street, dogs running etc. Learn where to focus to gain the most DoF, remember DoF can work both ways.
As an example, at many of the tracks I ran camera at, the camera position I ran, had cars coming to me. I would focus at the far end of the track and allow my DoF to cover me as the cars came towards me. Keep in mind these were 2/3 inch chips with lens that cost more than many new cars at the dealer AND when we built the units the video truck checked our backfocus (we did also but the had better monitors) and the backfocus is key. There really just isn't time to play around with focus when you'r trying to pick out a certain car that's coming to you at 190mph and the director is "talking" to you thru the headset. You've got to pick it up, frame it and follow it until he calls for the next shot. No time to focus, it's got to be right coming out of the corner.
Practice, check BF, check what you get for DoF forward and back at different f/stops, kearn the camera llike the back of your hand and you should be fine.
BTW, I know a guy that does motocross with a JVC HD100 and the Fuji16X lense. IT's a sharp as a tack so it can be done and done well.
Thankyou for your posts Don, it is fantastic for me to be able to get feedback from someone with your motorsport filming experience!

It is a measure of my inexperience that I had to look up what backfocusing means and after watching this Youtube clip I know I definitely need to buy Tim Dashwood's DVDs!
YouTube - Tutorial: HD100/200 How to set Backfocus on a professional lens

The fact that backfocus can be adjusted and your comments regarding DoF give me a lot more confidence that what I want to do is possible.
The maximum speed cars would be coming towards me is around 120mph and usually closer to 70mph.

In relation to physically adjusting the focus did you have controls on the handles of the camera?
If I get the GY-HM700 would I need to get some kind of remote control so I can zoom and focus while panning?

The accessory costs of these cameras are pretty frightening for my consumer eyes!
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Old February 27th, 2010, 10:28 PM   #10
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The cameras we used to do NASCAR (and IRL as well) are robotic cameras. We might be 1/4 mile away from the actual camera. The cameras were controlled thru fiber optic cables. There are control boxes on the tripods (big solid heavy Caronis-don't recall the number) and we used focus and zoom controls. These controls worked like the camera was on the tripod but were in fact not. Each camera also had a bank of monitors (corner, straight away, corner, top shot, that cameras preview and of course live shot depending on exactly which camera you were working) BUT it can be done off the shoulder with the right hand running zoom and the left focus and iris, just like a news event or slower moving sport like football (American) where while it appears to move fast it ain't running thru a turn at 150. And yes, I've done football, HS, College and Pro. I prefer cars, the weather is usually better.
Anyway I highly recommend a tripod, zoom and focus control and a studio setup so the monitor can be mounted on top of the camera. While it might not be any sharper than the LCD screen it will be bigger and that for me is a major thing. Even a 7 inch Marshall or something like it with a sunshade might work out fine. I prefer a zoom rocker on the right tripod handle, push left it goes wide, push right it goes tight. As for focus, JVC has a twist throttle handle but I prefer a wheel type. Don't know if JVC has it but to me it's faster and more precise than the twist type.

BTW, what I mean by adjusting the backfocus is t adjust so it is as sharp as atck thruout the zoom range. Sometimes we get it just enough but it needs to be 100% right so the DoF can help cover when you zoom to frame the car
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Last edited by Don Bloom; February 27th, 2010 at 10:33 PM. Reason: forgot to add
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