20x zoom lens -- various topics

Bill Ravens · December 27th, 2004, 08:02 AM

I've got all three lenses and find that I use the 20x most often. Beware of the focus hunting problem with the 20x, however, I beleive it's a tad sharper than the 16x manual. For my money, I'd invest in a good quality 6x9 monitor before I'd invest in a B&W viewfinder.

Pete Bauer · December 27th, 2004, 11:48 AM

If you go with the 20x and want to do artistic work, you'll almost certainly decide you need the 3x. The 20x is a long lens -- just plain not wide enough at the short end. The two together give you quite a lot of zoom range!

I've never used the 16x so can't comment on that. Here's good info posted by our fearless leader:

http://www.dvinfo.net/canonxl2/articles/article10.php

We'll look forward to seeing your work!

Daniel Kohl · January 20th, 2005, 08:36 AM

http://www.cinetechonline.com/index.html

The picture shows a follow-focus being used on a XL-2 20x servo lens. I wonder if there is something about the 20x servo lens that makes it possible to hit marks. That definitely is not the case with my 16x servo.

Does anyone know what Canon changed on the 20x servo, to make the focus ring direct drive?

Chris Hurd · January 20th, 2005, 10:57 AM

Hi Daniel,

There is no real difference there. You should contact Karl Horn of CineTech and get his input regarding the ability of that lens to hit marks using his follow focus rig (er ist auch ein Deutscher, übrigens). And then please report back and tell us what he told you.

Daniel Kohl · January 20th, 2005, 10:59 AM

Thanks Chris,

I will.

Daniel Kohl · January 21st, 2005, 10:19 AM

I just wrote an email to Cinetech:

"Are there any limitations, that I should know about, using the Cinetech Follow-Focus with my 16x servo lens? Like the Follow-Focus system is not designed to just make focusing "easier", is it?

I'm asking, because I find it hard to believe that a mechanical focusing system can get around the spongy speed sensitive servo focusing ring of the Canon 16x!

Just to make sure I'm getting this right, once I have set marks with the Cinetech Follow-Focus system, I will be able to consistently dial to these marks repeatedly, regardless of the dialing speed? If the answer to this is yes, I don't suppose you would explain how this is achieved?

I'm sorry for being so skeptical, and I don't expect you to divulge any trade secrets. But I don't believe that what I have just suggested is possible with a simply mechanical device. Maybe you can convince me that the FF overrides the speed sensitivity of the servo lens, without us having to go through the hassle of an international parcel post demo. Or do you have a Rep. here in Germany, where I could try out the system?"

I'll let you know how they respond.

Mark Sasahara · January 22nd, 2005, 04:17 PM

The experiment
Can the Canon 20x auto lens repeatedly and accurately hit preset focus marks?

The equipment
Canon XL2 w/20x auto lens, 16x manual lens, FU-1000 B&W viewfinder, mounted on Vinten Vision 3 head on Vision Tripod. Chrosziel bracket and rod holders, Cine Tech Titanium SL follow focus unit w/ coarse and fine pitch drive gears, coarse pitch gear ring for 20x auto lens. The 16x manual lens was used as the control lens. A matte box was not required for this experiment, so stock lens shades were used.

Settings
Aperture-f/2.2. Focal length-48mm*. Near focus point-11' 5.5". Far point-27' 11". Distances measured with a Stanley 100' steel tape and anchoring off the metal block that holds the rods on my Chrosziel matte box bracket. This approximate CCD location is based upon WAG. High contrast marks were used.
Notes:f/2.2 is maximum aperture at 48mm on the 20x lens. *Focal length was determined using the 16x manual lens and then making framing marks for the 20x. Camera aspect ratio set to 16x9, in manual.

Results Summary
Question: Can the Canon 20x auto lens accurately and repeatedly hit preset focus marks?
Answer: Yes and no
Explanation: If you set your marks and do not go beyond them, or change the zoom, you should be able to get repeatable results. Focus speed does seem to have some effect in making the marks drift. I was doing rather small pulls approximately sixteen feet between the near and far marks. The marks on the disc were about 3/8" apart, so I couldn't really zip between the two very quickly, without overshooting the mark.

I then zoomed wide and adjusted the focus, quickly going back and forth close and far distances a few times with the focus knob. The marks were obliterated by doing this and I had to reset the focus marks. Zooming shifted the marks also. This means that you cannot zoom in, get critical focus and then zoom back out to your shooting focal length. I did this, zooming in focusing and then zooming back out and the marks shifted significantly.

Shutting off the camera and then powering up again several times did not affect the focus marks. On powering up the focus mark that the camera was set to was sharp and shifting focus using the preset marks on the follow focus disc were accurate.

Mark Sasahara · January 22nd, 2005, 04:28 PM

Daniel, as part of the thread that this came from I have made a new thread with the results of my research on follow focus with the 20x auto lens.

"Canon 20x auto lens follow focus accuracy"
http://www.dvinfo.net/conf/showthrea...threadid=38166

This new thread you've started is good since I don't really know how the 20x auto lens works. Someone suggested that the firmware in the lens could be updated. This would be good because hard stops and footage/meter scales could be programmed in as well as a way to figure out what focal length you're at.

Can anyone hack the 20x?

Daniel Kohl · January 23rd, 2005, 03:45 AM

Thanks Mark,

You have confirmed what I suspected. Too bad, I would have love to have had the possibility of snap-to accurate focus, along with the image stabilizing of the auto lenses. I like to do a lot of hand held tele shooting. I guess you can't always have your cake and eat it at the same time.

Your little test here, has burst a tiny bubble of hope, but it has saved me a lot of time and trouble getting it to burst on my own.

Thanks again.

Rob Lohman · January 24th, 2005, 06:19 AM

Daniel: I'm wondering how you are going to do focus pulling and
do hand held shooting at the same time. Why not get the manual
lens to do the focus pulling when you need to (you should not
need OIS in this case anyway) and use the OIS lens when you
are going hand held.

Daniel Kohl · January 24th, 2005, 02:19 PM

Hi Rob,

I have found the image stabilizer on the 16x servo lens to be so good that my preferred method of shooting is with the lens very telephoto, and the camera braced under my arm. I'm not really only interested in focus pulls, I would like to be able to focus the servo lens consistently and be able to use techniques like judging the distance to the subject. What I would really like is a manual lens with the servo's image stabilization. But if there were such a thing, it would probably be out of my price class.

As to using a follow focus hand held, I'll admit that it is somewhat awkward, and you sweat a lot, but it is possible. And I have gotten good results shooting like this, with, and without an assistent. There are some prime lenses that are so stiff, you can only focus them with an arm or a FF.

Cheers,

Rob Lohman · January 24th, 2005, 04:09 PM

So if you are handheld in low mode I assume you are in a wide
angle shot? Do you really need that critical focus then? (since
your DoF should be pretty large)....

Daniel Kohl · January 24th, 2005, 04:34 PM

I like to shoot with a long focal length in this mode. Because I really like the look of the shallow DOF. Shooting from the hip like this also allows me to add a little movement to the camera and adjust to how the person or persons I am filming move. Without the stabilizer, I wouldn't be able to do this with half the focal length. I'm not into dogma style shaky camera work.

Joseph Andolina · February 17th, 2005, 11:14 AM

I'm not up much on filters at the moment, and need to find out what kind of filter I need to buy to protect my 20X lens from getting marked or scratched. I don;t want a filter that will minipulate the image, mainly for protection. Someone told me that it might be called a UV filter or Daylight filter? and would it be suitable for both interior and exterior shooting?
Thanks ahead of time.

Lauri Kettunen · February 17th, 2005, 01:10 PM

<<<-- Originally posted by Joseph Andolina : what kind of filter I need to buy to protect my 20X -->>>

Most likely Canon has a 72 mm filter called "Protect" as an accessory to the EF-series lenses. That should be a neutral glass and that should fit to the 20x lens. Ask some Canon rep./dealer about such filters. (I have myself a Canon 77mm Protect "filter", and pretty sure the same exists in other size.)

December 27th, 2004, 11:48 AM	#47
Pete Bauer Wrangler Join Date: May 2003 Location: Eagle River, AK Posts: 4,100	If you go with the 20x and want to do artistic work, you'll almost certainly decide you need the 3x. The 20x is a long lens -- just plain not wide enough at the short end. The two together give you quite a lot of zoom range! I've never used the 16x so can't comment on that. Here's good info posted by our fearless leader: http://www.dvinfo.net/canonxl2/articles/article10.php We'll look forward to seeing your work! __________________ Pete Bauer The most beautiful thing we can experience is the mysterious. It is the source of all true art and science. Albert Einstein Trying to solve a DV mystery? You may find the answer behind the SEARCH function ... or be able to join a discussion already in progress!

January 20th, 2005, 08:36 AM	#48
Daniel Kohl Contributor Join Date: Dec 2001 Location: Frankfurt, Germany Posts: 571	Follow-Focus for 20x servo lens works how? http://www.cinetechonline.com/index.html The picture shows a follow-focus being used on a XL-2 20x servo lens. I wonder if there is something about the 20x servo lens that makes it possible to hit marks. That definitely is not the case with my 16x servo. Does anyone know what Canon changed on the 20x servo, to make the focus ring direct drive? __________________ Daniel Kohl Frankenstein meets XL1

January 20th, 2005, 10:57 AM	#49
Chris Hurd Obstreperous Rex Join Date: Jan 2001 Location: San Marcos, TX Posts: 27,368 Images: 513	Hi Daniel, There is no real difference there. You should contact Karl Horn of CineTech and get his input regarding the ability of that lens to hit marks using his follow focus rig (er ist auch ein Deutscher, übrigens). And then please report back and tell us what he told you. __________________ CH Search DV Info Net \| 20 years of DVi \| ...Tuesday is Soylent Green Day!

January 20th, 2005, 10:59 AM	#50
Daniel Kohl Contributor Join Date: Dec 2001 Location: Frankfurt, Germany Posts: 571	Thanks Chris, I will. __________________ Daniel Kohl Frankenstein meets XL1

January 21st, 2005, 10:19 AM	#51
Daniel Kohl Contributor Join Date: Dec 2001 Location: Frankfurt, Germany Posts: 571	I just wrote an email to Cinetech: "Are there any limitations, that I should know about, using the Cinetech Follow-Focus with my 16x servo lens? Like the Follow-Focus system is not designed to just make focusing "easier", is it? I'm asking, because I find it hard to believe that a mechanical focusing system can get around the spongy speed sensitive servo focusing ring of the Canon 16x! Just to make sure I'm getting this right, once I have set marks with the Cinetech Follow-Focus system, I will be able to consistently dial to these marks repeatedly, regardless of the dialing speed? If the answer to this is yes, I don't suppose you would explain how this is achieved? I'm sorry for being so skeptical, and I don't expect you to divulge any trade secrets. But I don't believe that what I have just suggested is possible with a simply mechanical device. Maybe you can convince me that the FF overrides the speed sensitivity of the servo lens, without us having to go through the hassle of an international parcel post demo. Or do you have a Rep. here in Germany, where I could try out the system?" I'll let you know how they respond. __________________ Daniel Kohl Frankenstein meets XL1

December 27th, 2004, 08:02 AM	#46
Bill Ravens Join Date: Nov 2001 Location: santa fe, nm Posts: 3,264 Images: 10	I've got all three lenses and find that I use the 20x most often. Beware of the focus hunting problem with the 20x, however, I beleive it's a tad sharper than the 16x manual. For my money, I'd invest in a good quality 6x9 monitor before I'd invest in a B&W viewfinder.

January 22nd, 2005, 04:17 PM	#52
Mark Sasahara Major Player Join Date: Oct 2004 Location: NYC Posts: 649	Canon 20x auto lens follow focus accuracy The experiment Can the Canon 20x auto lens repeatedly and accurately hit preset focus marks? The equipment Canon XL2 w/20x auto lens, 16x manual lens, FU-1000 B&W viewfinder, mounted on Vinten Vision 3 head on Vision Tripod. Chrosziel bracket and rod holders, Cine Tech Titanium SL follow focus unit w/ coarse and fine pitch drive gears, coarse pitch gear ring for 20x auto lens. The 16x manual lens was used as the control lens. A matte box was not required for this experiment, so stock lens shades were used. Settings Aperture-f/2.2. Focal length-48mm. Near focus point-11' 5.5". Far point-27' 11". Distances measured with a Stanley 100' steel tape and anchoring off the metal block that holds the rods on my Chrosziel matte box bracket. This approximate CCD location is based upon WAG. High contrast marks were used. Notes:f/2.2 is maximum aperture at 48mm on the 20x lens. Focal length was determined using the 16x manual lens and then making framing marks for the 20x. Camera aspect ratio set to 16x9, in manual. Results Summary Question: Can the Canon 20x auto lens accurately and repeatedly hit preset focus marks? Answer: Yes and no Explanation: If you set your marks and do not go beyond them, or change the zoom, you should be able to get repeatable results. Focus speed does seem to have some effect in making the marks drift. I was doing rather small pulls approximately sixteen feet between the near and far marks. The marks on the disc were about 3/8" apart, so I couldn't really zip between the two very quickly, without overshooting the mark. I then zoomed wide and adjusted the focus, quickly going back and forth close and far distances a few times with the focus knob. The marks were obliterated by doing this and I had to reset the focus marks. Zooming shifted the marks also. This means that you cannot zoom in, get critical focus and then zoom back out to your shooting focal length. I did this, zooming in focusing and then zooming back out and the marks shifted significantly. Shutting off the camera and then powering up again several times did not affect the focus marks. On powering up the focus mark that the camera was set to was sharp and shifting focus using the preset marks on the follow focus disc were accurate. __________________ Mark Sasahara Director of Photography

January 22nd, 2005, 04:28 PM	#53
Mark Sasahara Major Player Join Date: Oct 2004 Location: NYC Posts: 649	Daniel, as part of the thread that this came from I have made a new thread with the results of my research on follow focus with the 20x auto lens. "Canon 20x auto lens follow focus accuracy" http://www.dvinfo.net/conf/showthrea...threadid=38166 This new thread you've started is good since I don't really know how the 20x auto lens works. Someone suggested that the firmware in the lens could be updated. This would be good because hard stops and footage/meter scales could be programmed in as well as a way to figure out what focal length you're at. Can anyone hack the 20x? __________________ Mark Sasahara Director of Photography

January 23rd, 2005, 03:45 AM	#54
Daniel Kohl Contributor Join Date: Dec 2001 Location: Frankfurt, Germany Posts: 571	Thanks Mark, You have confirmed what I suspected. Too bad, I would have love to have had the possibility of snap-to accurate focus, along with the image stabilizing of the auto lenses. I like to do a lot of hand held tele shooting. I guess you can't always have your cake and eat it at the same time. Your little test here, has burst a tiny bubble of hope, but it has saved me a lot of time and trouble getting it to burst on my own. Thanks again. __________________ Daniel Kohl Frankenstein meets XL1

January 24th, 2005, 06:19 AM	#55
Rob Lohman RED Code Chef Join Date: Oct 2001 Location: Holland Posts: 12,514	Daniel: I'm wondering how you are going to do focus pulling and do hand held shooting at the same time. Why not get the manual lens to do the focus pulling when you need to (you should not need OIS in this case anyway) and use the OIS lens when you are going hand held. __________________ Rob Lohman, visuar@iname.com DV Info Wrangler & RED Code Chef Join the DV Challenge \| Lady X Search DVinfo.net for quick answers \| Buy from the best: DVinfo.net sponsors

January 24th, 2005, 02:19 PM	#56
Daniel Kohl Contributor Join Date: Dec 2001 Location: Frankfurt, Germany Posts: 571	Hi Rob, I have found the image stabilizer on the 16x servo lens to be so good that my preferred method of shooting is with the lens very telephoto, and the camera braced under my arm. I'm not really only interested in focus pulls, I would like to be able to focus the servo lens consistently and be able to use techniques like judging the distance to the subject. What I would really like is a manual lens with the servo's image stabilization. But if there were such a thing, it would probably be out of my price class. As to using a follow focus hand held, I'll admit that it is somewhat awkward, and you sweat a lot, but it is possible. And I have gotten good results shooting like this, with, and without an assistent. There are some prime lenses that are so stiff, you can only focus them with an arm or a FF. Cheers, __________________ Daniel Kohl Frankenstein meets XL1

January 24th, 2005, 04:09 PM	#57
Rob Lohman RED Code Chef Join Date: Oct 2001 Location: Holland Posts: 12,514	So if you are handheld in low mode I assume you are in a wide angle shot? Do you really need that critical focus then? (since your DoF should be pretty large).... __________________ Rob Lohman, visuar@iname.com DV Info Wrangler & RED Code Chef Join the DV Challenge \| Lady X Search DVinfo.net for quick answers \| Buy from the best: DVinfo.net sponsors

January 24th, 2005, 04:34 PM	#58
Daniel Kohl Contributor Join Date: Dec 2001 Location: Frankfurt, Germany Posts: 571	I like to shoot with a long focal length in this mode. Because I really like the look of the shallow DOF. Shooting from the hip like this also allows me to add a little movement to the camera and adjust to how the person or persons I am filming move. Without the stabilizer, I wouldn't be able to do this with half the focal length. I'm not into dogma style shaky camera work. __________________ Daniel Kohl Frankenstein meets XL1

February 17th, 2005, 11:14 AM	#59
Joseph Andolina Regular Crew Join Date: Mar 2004 Location: Everett, WA Posts: 178	proper filter for 20X lens protection? I'm not up much on filters at the moment, and need to find out what kind of filter I need to buy to protect my 20X lens from getting marked or scratched. I don;t want a filter that will minipulate the image, mainly for protection. Someone told me that it might be called a UV filter or Daylight filter? and would it be suitable for both interior and exterior shooting? Thanks ahead of time.

February 17th, 2005, 01:10 PM	#60
Lauri Kettunen Major Player Join Date: Aug 2004 Location: Kangasala, Finland Posts: 445	Re: proper filter for 20X lens protection? <<<-- Originally posted by Joseph Andolina : what kind of filter I need to buy to protect my 20X -->>> Most likely Canon has a 72 mm filter called "Protect" as an accessory to the EF-series lenses. That should be a neutral glass and that should fit to the 20x lens. Ask some Canon rep./dealer about such filters. (I have myself a Canon 77mm Protect "filter", and pretty sure the same exists in other size.)