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DVX100 Focus Table

Published : 13th June 2004


Greetings,

Found this site that has a table that has focus distances for the "percentages" used in the viewfinder :

http://www.flickerfactory.com/egp/morestuff/dvx100focus.htm

I haven't had time to test the correlation myself but it looks like someone's taking some time and effort over them.

Cheers

Kim Sargenius
(recently graduated) student shooter
Sydney



>Found this site that has a table that has focus distances for the >"percentages" used in the viewfinder :

Great, I can definitely use that. I've come up with a table that correlates "Z" score to DVX and 35mm SLR focal lengths.

Cheers,

Franco
Zurich, Switzerland



>Found this site that has a table that has focus distances for the >"percentages" used in the viewfinder :

Kim,

I went to the site and downloaded the excel version of the chart. I
have a DVX100 and the numbers that I've checked so far appear to be right on the money with my camera. Pretty Cool.

Marten Benatar



>have a DVX100 and the numbers that I've checked so far appear to be >right on the money with my camera. Pretty Cool

The wonders of modern communications.

Thanks should go to Evin Grant who compiled the table and posted it to 2-pop originally, and thanks to Eric Gustavo Petersen who posted it where I found it.

Thanks for checking those numbers with your camera Marten!

Cheers,

Kim Sargenius
(recently graduated) student shooter
Sydney



If this table is indeed accurate, it begs the question as to why Panasonic stuck a pointless 0-99 scale in the viewfinder instead of an actual measured distance in either feet or meters. How complicated could that math possibly be? I'm no programmer but I bet I could write that code in less than a day.

The little Chrosziel follow focus with mechanical stop points at either end of the scale is very nice and with this conversion table it suddenly makes this camera far more functional.

Mitch Gross
NYC DP



>If this table is indeed accurate, it begs the question as to why Panasonic >stuck a pointless 0-99 scale in the viewfinder

Jan?

>The little Chrosziel follow focus with mechanical stop points at either >end of the scale is very nice

When AC's go metric -- imagine that; an FF disk marked 0 – 99.

Cheers,

Kim Sargenius
(recently graduated) student shooter
Sydney



Mitch and Kim asked:

>If this table is indeed accurate, it begs the question as to why Panasonic >stuck a pointless 0-99 scale in the viewfinder... Jan?

This is a very nice little chart if you work on the side of the world that does feet and inches but if Panasonic had put the feet and inches in rather than percentages in the camera, the part of the world that works in meters, would not find it so useful.

Percentages work, the numbers are repeatable, and if you really need the physical measurements, people will figure it out, just like the very talented person that made the chart.

Hope that helps,

Jan Crittenden



Jan Crittenden writes :

>Percentages work, the numbers are repeatable, and if you really need >the physical measurements, people will figure it out, just like the very >talented person that made the chart.

Your supposition that people from different parts of the globe don't always work in feet and inches but then they are probably not working in NTSC either, so if you are going to make a PAL camera, then mark it in meters, NTSC use feet and inches.

Although having been a DP for a whole bunch of years, meters as an increment of measure is not foreign to me and easy enough to use to judge distance...however I would never expect my AC to roll out his percentage tape to mark focus points!

Just a thought!

Allen S. Facemire
DP/Director
SaltRun Productions,inc.
Atlanta
www.saltrunproductions.com



Allen Facemire suggested :

>Your supposition that people from different parts of the globe don't >always work in feet and inches but then they are probably not working >in NTSC either, so if you are going to make a PAL camera, then mark it >in meters, NTSC use feet and inches.

Then what about Japan, they are NTSC and meters?

Best regards,

Jan Crittenden



>This is a very nice little chart if you work on the side of the world that >does feet and inches but if Panasonic had put the feet and inches in >rather than percentages in the camera, the part of the world that works in >meters, would not find it so useful.

Jan,

How hard would it have been to give the user a menu setting where they get to choose imperial or metric units? Or percentages, if that's the type of tape measure they have

Every so often a manufacturer makes a big time balls-up with a 'feature' on a product... And then the silly ones make an even bigger mistake trying to market it as a deliberate feature.

Cheers,

Clive Woodward
video technician
Perth, Western Australia



Jan remarked :

>Then what about Japan, they are NTSC and meters?

Point taken but like as I explained before, I'd take meters over percentages any day.

Show me a percentage tape measure!

Allen S. Face mire
DP/Director
SaltRun Productions,inc.
Atlanta



Jan --

That's got to be one of the weakest arguments I've ever heard, and I think a specious one. Surely Panasonic could make a menu choice for the use of either Imperial (feet) or Metric measurements. These are two fully matured distance measurement systems that are universally understood by anyone who will ever use this camera. (I don't think Panasonic would have to worry about any lost tribes deep in the Amazon or Congo that don't know either system.) The percentage measurements are meaningless to the normal people of the world (i.e. people who are not technical engineers at large electronics companies) and do not correspond to any system currently in use. It is the Esperanto of distance measurement.

Panasonic could have at least had the courtesy to create a chart to map out feet and meter distances. Would that be so hard to put in the manual? Rather than Panasonic not wanting to make some politically incorrect choice about feet or metric, it simply appears like no one wanted to bother. Love the camera--hate this non-feature.

Mitch Gross
NYC DP



My little Olympus still camera allows you to choose either feet or meters in it's manual focus scale.

I think this is an example of a decision made not to spend the extra effort, on the idea that most of the buyers of a 3 thousand dollar camera wouldn't be using measuring tape, but would maybe be pulling focus. So a repeatable scale was put in. So it looks like they were not right, there are users who want this.

I don't know why people feel it is necessary to get so upset and angry and derisive. Every company makes decisions like this. I've never seen a product that was perfect for me or others. You give your feedback, and maybe the next model is improved.

Steven Bradford
Seattle



>I think this is an example of a decision made not to spend the extra >effort, on the idea that most of the buyers of a 3 thousand dollar camera >wouldn't be using measuring tape, but would maybe be pulling focus.

I thought the focus scale was a joke also and then last week I shot with it. You are correct: 90% of the time, people who use this camera are going to be doing their own focus. I actually found it fairly easy to do simple follow focus and rack focus by just zooming in: getting "the numbers" and then remembering "she's at 67, he's at 85 and then he moves to 80."

I'm normally a real traditionalist with these things, but overall, I didn't mind this new system. My biggest complaint (as with both the PD-150 and the XL-1), is the ergonomics of the controls, esp. getting to the iris control when the flip-out viewfinder is open.

This is not to say that I approve of this numerical system for the focus, it would be very difficult for those occasions when you do have an AC who is using a measuring tape. It really would not be difficult for them to make it switchable to feet and meters.

Blain Brown
DP
LA



Mitch

>It is the Esperanto of distance measurement.

You wouldn't happen to know where I could find an Esperanto tape measure to match???

>Panasonic could have at least had the courtesy to create a chart to map >out feet and meter distances. Would that be so hard to put in the >manual?

No offence to Panasonic but this would seem to be the obvious thing to do

As it stands I bet someone could make a nice pile of cash by printing and laminating this table in a nice A6 size that would fit in your pocket -- I'm sure some entrepreneurial soul somewhere must have thought of it...

Cheers,

Kim Sargenius
(recently graduated) student shooter
Sydney



>You wouldn't happen to know where I could find an Esperanto tape >measure to match???

Actually, I think that if I were to do an extended shoot with this camera I might just take a standard tape measure and mark the Panasonic scale on it for convenience.

Mitch Gross
NYC DP



Mitch,

All it was, was a potential answer, I really have no clue. I am not the product manager nor the product designer. Point was that it may be one reason why they did it. I really don't know. I don't want to be barbequed over the answer I offered, there is no answer from the folks that designed and that is all there is to it.

Sorry,

Jan Crittenden



>standard tape measure and mark the Panasonic scale on it for

Makes sense, though not in the Esperanto spirit

Cheers,

Kim Sargenius
(recently graduated) student shooter
Sydney



>All it was, was a potential answer, I really have no clue. I am not the >product manager nor the product designer.

Jan --

Sorry if I overreacted to your post. You provide great info about Panasonic products both on and off the list and I didn't mean to impugn you or your comments. I consider the focus issue a poor move on someone at Panasonic but I shouldn't take that out on you. I do apologize.

Mitch Gross
NYC DP



>Actually, I think that if I were to do an extended shoot with this camera I >might just take a standard tape measure and mark the Panasonic scale >on it for convenience.

And then when the talent misses his mark by a foot and a half, I set my focus to... to...

Jan says :

>I don't want to be barbequed over the answer I offered, there is no >answer from the folks that designed and that is all there is to it.

Jan, I appreciate that you monitor CML and are available for questions. Nonetheless, I am constantly amazed at the amount of speculation that occurs here. Lack of technical information from every manufacturer (not to harp solely on Panasonic) keeps us guessing at best. I, for one, would appreciate a more readily available conduit to the engineers of a product. I understand that an engineer can't be sitting at his desk all day answering emails, but it's at times absurd to hear us guessing about things that have a definitive answer.

And in case you misinterpret -- thanks for being here.

Chris Mosio
Cinematographer/Seattle



Hopefully the chart is accurate. Right now, I have some time free, I'll do a brief test. A DoF chart would truly be ideal!

Illya Friedman
Senior Camera Rental Agent
Moviola Cameras
Hollywood, CA
www.moviola.com



>Lack of technical information from every manufacturer (not to harp >solely on Panasonic) keeps us guessing at best. I, for one, would >appreciate a more readily available conduit to the engineers of a >product.

It's not about engineering it's about market positioning.

Geez, if you want a focussing scale in standard units of measurement next you'll be wanting a zoom that holds focus....

Sam "give em a foot and they'll want a meter" Wells



>Hopefully the chart is accurate.

I used it all day yesterday and it seems to be quite accurate.

Mike Most
VFX Supervisor
IATSE Local 600
Los Angeles



If this focus scale is indeed accurate, then I think there may be an elegant mod for the camera. The Chrosziel follow focus setup includes mechanical stops for the focus ring and gives repeatable focus control. It also has a marking disk for both the follow focus knob and wrapped around the lens itself. It should be fairly easy to stencil marks onto the lens itself (well, the ring mounted to the lens) and now these marks are forever accurate, just like a normal focus scale on lenses like we're used to. It sounds so simple that I'm still baffled as to why Panasonic never did it.

One thing I would note is that I have noticed that whenever I put a lens adapter onto a main lens it shifts the focus points. The .6x wide angle from Century that I use on my DV500 shifts all the focus marks about a centimetre on the scale. I had to write up a secondary focus scale for it on an offset for reference. This would likely need to be done for any wide angle or other lens adapter (telephoto, anamorphic) for the DVX100 as well. Still, it removes one of my major gripes about this camera.

Mitch Gross
NYC DP



>It sounds so simple that I'm still baffled as to why Panasonic never did it.

You have to remember that at the consumer and even prosumer level in camera technology these days, the whole idea of users thinking in focal distances has been superseded by elaborate automation.

This is what I meant by "its marketing not engineering", of course it is engineering but it's engineering designed to replace your brain with something more advanced, supposedly.

Not dissing the DVX camera per se...

Sam Wells



>It should be fairly easy to stencil marks onto the lens itself (well, the ring >mounted to the lens) and now these marks are forever accurate, just >like a normal focus scale on lenses like we're used to. It sounds so >simple that I'm still baffled as to why Panasonic never did it.

They never did it for a few reasons. First, the marks themselves could not be accurate because the focus ring is a no-end-stop, servo focus mechanism that is velocity sensitive and not repeatable because it's not mechanical. The follow focus works as long as you don't make very rapid movements, because when you do, the marks change. The numbers are accurate because they're always reading the current setting.

Personally, I don't really see any reason to not offer a choice of displays : percentage, feet/inches, and meters/cm. And possibly a side mounted readout of this for the focus puller (unlikely).

Mike Most
VFX Supervisor
IATSE Local 600
Los Angeles



Illya Frieman wrote :

>Hopefully the chart is accurate. Right now, I have some time free I'll do a >brief test. A DoF chart would truly be ideal!"

If an when you do that, try it with a .07 wide angle adaptor. The close focus % base value starts well below 50%. I'm guessing because of the wide angle lens!

Allen S. Face mire
DP/Director
SaltRun Productions,inc.
Atlanta



At the risk of sounding ignorant, I'm curious why this focus table is so important.

Considering that you can see the results right there in the viewfinder, on the LCD monitor, and on your external NTSC monitor, I don't see the point.

Dan Coplan
Cinematographer/Editor/DVD Authoring
www.dancoplan.com



Dan Coplan wrote:

>At the risk of sounding ignorant, I'm curious why this focus table is so >important. Considering that you can see the results right there in the >viewfinder, on the LCD monitor, and on your external NTSC monitor, I >don't see the point.

Neither the LCD nor the viewfinder are really good enough for accurate focusing, and any back focus issues can cloud the accuracy of focus done by the "normal" video zoom lens routine (zoom in, focus, zoom back out to desired focal length). In many cases, the operator doesn't have an external NTSC monitor anywhere near the camera. I'd much rather trust an accurate measurement than anyone's eyes looking at a small LCD screen.

Not to mention that measuring while setting marks often takes less time than putting the actors on those marks just prior to shooting and then doing the zoom in/set focus/zoom out routine, especially when there are multiple marks to hit during the shot. In some cases, considerably less time, especially when shooting in dark, moody lighting where it's difficult to see an image on those screens in the first place.

Mike Most
VFX Supervisor
IATSE Local 600
Los Angeles



>It should be fairly easy to stencil marks onto the lens itself... and now >these marks are forever accurate, just like a normal focus scale...I'm still >baffled as to why Panasonic never did it.

Unfortunately the focus needs to be recalibrated to infinity on every power up, so if you mark the lens ring, you're SOL the next time you power off. With the FF control, you can just spin the puppy to infinity, set the limit-stop, and you're good to go as long as power remains applied.

>And possibly a side mounted readout of this for the focus puller

The side mounted display for the focus puller is the LCD, flipped around and folded back against the body. Works very well for that purpose.

Cheers,

Adam Wilt / Video Geek / Menlo Park CA USA



Adam Wilt wrote :

>The side mounted display for the focus puller is the LCD, flipped around >and folded back against the body. Works very well for that purpose.

Ooohh, clever idea. Never really thought of that. I'll try it. Thanks. (Of course, when the operator wants to use the LCD instead of the viewfinder, well...)

Mike Most
VFX Supervisor
IATSE Local 600
Los Angeles



Adam Wilt wrote :

>Unfortunately the focus needs to be recalibrated to infinity on every >power up, so if you mark the lens ring, you're SOL the next time you >power off. With the FF control, you can just spin the puppy to infinity, set >the limit-stop, and you're good to go as long as power remains applied.

I have run into the power off issue a number of times, but I've also found that even when maintaining power, the focus ring seems to be velocity sensitive. I've set marks on a follow focus that just seem to change whenever the knob is turned rapidly. They don't seem to slip when it's changed at a more, shall we say, leisurely rate. I really don't think it's my imagination.

Mike Most
VFX Supervisor
IATSE Local 600
Los Angeles



Guys,

On cameras of this nature, the focus ring has no direct connection to the lens optics, but is simply a "user interface" to the camera's electronics, which then controls the optic via servo-motors. And in the case of the DVX-100, the servo feedback reads out as a percent scale.

These cameras don't have a true "zoom" lens, rather what is technically known as a "vari-focal" lens. A zoom lens keeps focus as the image magnification changes. Hence the "zoom in and focus then zoom out to frame the shot" routine we've had drummed into us from cinematic kindergarten.

A vari-focal lens doesn't permit this. It is optically much simpler (fewer elements). Vari-focal lenses are common in the fixed surveillance camera game. It is only recently (starting with the Canon XL-1?) that manufacturers have decided to use vari-focal lenses with electronics that simultaneously control the "magnification" optic and focus optic, to create a zoom effect and/or a focus shift!

A further "enhancement", now that the mechanical connection isn't possible, is to put a variable-speed algorithm into the electronics so that a fast twist of the focus "control" will change the focus more that a slow twist, even if the degree of twist is the same. (Most computer mice exhibit this behaviour)

Hence adding chinagraph pencil markings to the un-calibrated rings on these domestic cameras isn't going to achieve repeatable results.

Clive Woodward,
video techie who prefers real bottles
Perth, Western Australia.



>and any back focus issues can cloud the accuracy of focus done by the >"normal" video zoom lens routine

By this do you mean if the back focus is off, the zoom lens routine won't be accurate? Because if the back focus is off, wouldn't the measurements also be off?

>Not to mention that measuring while setting marks often takes less time >than putting the actors on those marks just prior to shooting and then >doing the zoom in/set focus/zoom out routine

Focusing to a star chart would be the quickest, most accurate solution I'm guessing. Rather than running the tape from camera to mark and looking up the conversion. And by noting the focus number on the camera for each mark, you'd be all set.

>especially when shooting in dark, moody lighting where it's difficult to >see an image on those screens in the first place.

I'm with you there! Focus on that camera in low light is near impossible.

Dan "Not Arguing...Understanding" Coplan



>I've also found that even when maintaining power, the focus ring seems >to be velocity sensitive...I really don't think it's my imagination.

You're probably right, Mike. I haven't tried to break it this way (but will this weekend if I get a chance). It's a common problem with these servo lenses. In fact, I'd be surprised if I *couldn't* screw it up this way : position encoders have clean working ranges, and can drop bits when turning too fast or too slow.

So your idea of "it's OK as long as you don't whip-focus it" sounds good to me.

Adam Wilt


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