20x zoom lens -- various topics

Daniel Paquin · November 23rd, 2007, 02:10 PM

WOW, it sure does help!

Excellent explanation, very detailed.

I’ve thought the lighting was different because they were using different type of bulbs. From your explanation it has nothing to do with being different type of bulbs but with the fact they the bulbs are aging i.e should be replaced.

You are right, I would be really lucky to get the arena manager to change their bulbs because of that. To them the bulb is still providing lighting, why changing it when your not in the dark.

It does make a lot of sense, last week-end I’ve filmed within another arena. I had no problems. Yes, there were lights which we old but not to the same extent than the previous week-end.

This is also true, being honest with clients is the best way to go. This is what I have been doing and the clients appreciate when you do not hide things.

Unfortunately, in my situation I cannot do post editing. It’s filmed, it’s put live on DVD, it’s finalised and the client leaves the arena with his souvenir in his hand.

Merci beaucoup Gabriel, c’est très apprécié !

Thanks everybody for your help.

Daniel

Piotr Zubik · January 8th, 2008, 02:50 PM

Hi everybody!

This is my first post - I've been reading this forum (which is always of great help) for a year now bo it wasn't until I got a problem with my camera that I decided to register and write my first post.

I believe I've read every single topic about it and still don't know if I my camera suffers from it or not. What's more my problems seems a little bit different. So here it goes (it's gonna be long):

Few months ago I bought a new XL2 in the UK from a reputable seller on Ebay. The camera was brand new, everthing (box etc) packed as it should be. So many times have I read about the dreaded backfocus issue with XL2 so it was the first thing I checked when I opened the box. The camera seemed to be fine.

Few days I ago when I was playing with Adobe OnLocation I discovered that although I got crtical focus (zoom in, focus, zoom out) my screen seemed a little bit soft when full wide. I spent many hours staring at the monitor and it appears I've got a backfocus problem, however, it is not like for many other guys here - after I zoom out, everything does not get horribly blurred but is somewhat softer not much but can be easily noticed (not in the viewfinder though).

Yeah, I know when fully wide XL2 (SD) is not a Panavision Genesis and loose some detail but actually I am able to correct (!) the focus bu turning the lens ring about 1 cm left, then the shot gets sharper. I noticed that the biggest difference is when I open iris all the way up to f 1.6. When the iris is at 5.6 or 4 I'm having a hard time looking for out of focus shot but I think it's still there (just smaller) and once again I can correct it by turning the focus ring left.

I thought I'm focusing incorectly, but I tried every option: zoom in, autofocus on, get the focus, then off, zoom out. It's all the same in the end - When fully wide I can correct the focus either manually or by aplying autofocus once again.

What's intersting, especially at f 1.6 when I zoom in, focus, zoom out, what's really in focus is not the subject but the plane that is about two ft. from the camera (providing my subject is about 2 meters away). When I correct the focus and my subject is really focused then this plane is softer.
I read somewhere that when adjusting backfocus on manual lens one should open the iris as much as possible so it may some clue why I see this at f 1.6 better.

My question is: Does this count as a backfocus issue? I will repeat this once again: when I get the critical focus the difference in sharpness is very small.
On the other hand, when I see a shot that i properly focused ( not very often happens due to a viewfinder anyway) I am blown away by the quality of picture my XL2 produces. What's more, even if less sharpness is more "filmlike" and more is 'videoish' I would prefer to destroy my picture in post and not by shooting it out of focus.

Normally, I live in Poland so I guess if I take my camera to Canon I will have to pay for the adjustment but Im'willing to do it since it wil take few month when I will be in the UK once again. BTW. Is backfocus adjustment on the stock lens done by any authorized Canon service center or it has to go to the factory or what?

Please guys, share your knowledge and experience. Thanks for reading and sorry for such long and boring post...

Piotr

Ryan Mueller · January 11th, 2008, 10:04 AM

Hi Piotr,

I think the reason that you are not getting any response on this is due to the fact that this issue has been covered extensively in the past. If you do a search for XL2 backfocus, you should be able to find plenty of information on your topic.

I will tell you this though, the stock 20x XL2 lens has been known to be shipped with backfocus issues. Judging by your description, you have a backfocus issue that needs to be resolved through Canon.

Good Luck!
Ryan

Piotr Zubik · January 12th, 2008, 04:49 AM

Thank you Ryan for your reply!
These are not good news for my XL2 but I'm glad I know what the problem may be.

BTW. Yeah, I know it's been covered many times before, but as I wrote my problem is a little bit different (very small difference, seen mostly at f 1.6) and I did not find the definite answer in other topics as everybody had huge backfocus issue, everything blurred, only one guy mentioned about f stops,which still only similar to my problem.... Sorry for bringing out this already discussed topic.

Anyway, as you said, I think I will have to take my camera to Canon...

Thanks once again for your help.

Ryan Mueller · January 12th, 2008, 10:04 AM

What you are experiencing with the f-stop difference is typical of all lenses, the higher the f-stop; the more that will be in focus. The lower the f-stop; less will be in focus therefore giving you a very shallow depth of field. For instance: you are shooting an interview with a person 6 feet away from the background, at an f-stop of 1.6 the subject will be in focus and the background will be slightly out of focus while at an f-stop of 5.6 the subject will be in focus while the background is more likely to be in focus as well.

The bottom line is: if you zoom in and get critical focus then zoom back out and the focal point changes, you have a backfocus issue. This is true for any f-stop (especially a lower f-stop).

Hope this helps,
Ryan

Piotr Zubik · January 12th, 2008, 12:44 PM

Thank you Ryan for a detailed response. I know what DOF is and how to achieve it via iris adjustment, but frankly speaking I didn't know how it is related to backfocus issue at full wide shot.

"The bottom line is: if you zoom in and get critical focus then zoom back out and the focal point changes, you have a backfocus issue. This is true for any f-stop (especially a lower f-stop)." This is 100% what I needed to know!

Thanks,
Piotr

Greg Boston · January 12th, 2008, 01:21 PM

Piotr,

Also be advised that the stock 20x lens will close the iris down a couple stops as yo go full telephoto. The 16x manual lens is nice in this regard since it has manual back focus adjustment and will hold iris full open at the telephoto end. If you plan to keep the XL2 for awhile, the manual lens is a great investment IMHO.

Enjoy your new camera!

-gb-

Piotr Zubik · February 1st, 2008, 05:52 AM

UPDATE: I have just called my closest authorized service center. The lady on the phone gave me the price for backfocus adjustment (quite high) and told me that THE TECHNICIAN SAID THAT SOME XL2s CAN'T HAVE BACKFOCUS ADJUSTED PROPERLY DUE TO A "BUG" IN THIS MODEL.

Have you ever heard of such thing? Can I get stuck with the lens that can't be fixed and the only solution to get rid of this tiny backfocus issue would be purchasing new stock 20x? The more i'm into this the more I'm considering Greg's advice on buying canon 16x full manual lens (still beyond my financial capabilities)

Jonathan Kirsch · February 22nd, 2008, 02:56 PM

Pioter,

Did the person you talk to say how to find out if you have the model with the 'bug' in it? I'd like to know if mine is one of those models. I'm thinking my backfocus issus is...back.

Jonathan

Piotr Zubik · February 23rd, 2008, 11:51 AM

Jonathan,

I didn't spoke directly to the technician, only the receptionist who asked somebody in the background so she might have simplfied some stuff. However, when I emailed another canon service center they didn't tell me there's a bug or whatever, they just said that the price will depend on if it is only lens that need adjusting or lens and the camera body. Coud this mean the guys at previous center were wrong or just couldn't fix some XL2 backfouses int the past so they made up some BUG excuse? (that center though being authorized by Canon, are repairing several brands as well so maybe that's the reason)

In two or three weeks I will be taking my XL2 to the second service center to solve backfocus AND some excessive noise (not dependent on gain custom settings) which I think I'm getting in light and dark places almost equally. It is not far away so I hope I will have the chance to speak to someone about this BUG and other issues.

I must admit that after initial 'love' with the XL2 (when everything seemed extremely perfect because I did not have the chance to inspect everything properly) I'm somewhat depressed - first backfocus, then this alleged noise that I noticed and THEN you are saying that your backfous problem is BACK meaning that once repaired it may need to be done again. This is really bad providing backfous is quite pricey to fix :(

Anyway, I will keep you informed.

Piotr

November 23rd, 2007, 02:10 PM	#241
Daniel Paquin Regular Crew Join Date: Jan 2005 Location: Québec, Canada Posts: 179	WOW, it sure does help! Excellent explanation, very detailed. I’ve thought the lighting was different because they were using different type of bulbs. From your explanation it has nothing to do with being different type of bulbs but with the fact they the bulbs are aging i.e should be replaced. You are right, I would be really lucky to get the arena manager to change their bulbs because of that. To them the bulb is still providing lighting, why changing it when your not in the dark. It does make a lot of sense, last week-end I’ve filmed within another arena. I had no problems. Yes, there were lights which we old but not to the same extent than the previous week-end. This is also true, being honest with clients is the best way to go. This is what I have been doing and the clients appreciate when you do not hide things. Unfortunately, in my situation I cannot do post editing. It’s filmed, it’s put live on DVD, it’s finalised and the client leaves the arena with his souvenir in his hand. Merci beaucoup Gabriel, c’est très apprécié ! Thanks everybody for your help. Daniel __________________ Daniel Paquin Production ZoOM vidéo

January 8th, 2008, 02:50 PM	#242
Piotr Zubik Regular Crew Join Date: Jan 2008 Location: Miedzyrzec Podlaski, POLAND Posts: 30	XL2 Stock Lens 20x Backfocus? Or something different. Hi everybody! This is my first post - I've been reading this forum (which is always of great help) for a year now bo it wasn't until I got a problem with my camera that I decided to register and write my first post. I believe I've read every single topic about it and still don't know if I my camera suffers from it or not. What's more my problems seems a little bit different. So here it goes (it's gonna be long): Few months ago I bought a new XL2 in the UK from a reputable seller on Ebay. The camera was brand new, everthing (box etc) packed as it should be. So many times have I read about the dreaded backfocus issue with XL2 so it was the first thing I checked when I opened the box. The camera seemed to be fine. Few days I ago when I was playing with Adobe OnLocation I discovered that although I got crtical focus (zoom in, focus, zoom out) my screen seemed a little bit soft when full wide. I spent many hours staring at the monitor and it appears I've got a backfocus problem, however, it is not like for many other guys here - after I zoom out, everything does not get horribly blurred but is somewhat softer not much but can be easily noticed (not in the viewfinder though). Yeah, I know when fully wide XL2 (SD) is not a Panavision Genesis and loose some detail but actually I am able to correct (!) the focus bu turning the lens ring about 1 cm left, then the shot gets sharper. I noticed that the biggest difference is when I open iris all the way up to f 1.6. When the iris is at 5.6 or 4 I'm having a hard time looking for out of focus shot but I think it's still there (just smaller) and once again I can correct it by turning the focus ring left. I thought I'm focusing incorectly, but I tried every option: zoom in, autofocus on, get the focus, then off, zoom out. It's all the same in the end - When fully wide I can correct the focus either manually or by aplying autofocus once again. What's intersting, especially at f 1.6 when I zoom in, focus, zoom out, what's really in focus is not the subject but the plane that is about two ft. from the camera (providing my subject is about 2 meters away). When I correct the focus and my subject is really focused then this plane is softer. I read somewhere that when adjusting backfocus on manual lens one should open the iris as much as possible so it may some clue why I see this at f 1.6 better. My question is: Does this count as a backfocus issue? I will repeat this once again: when I get the critical focus the difference in sharpness is very small. On the other hand, when I see a shot that i properly focused ( not very often happens due to a viewfinder anyway) I am blown away by the quality of picture my XL2 produces. What's more, even if less sharpness is more "filmlike" and more is 'videoish' I would prefer to destroy my picture in post and not by shooting it out of focus. Normally, I live in Poland so I guess if I take my camera to Canon I will have to pay for the adjustment but Im'willing to do it since it wil take few month when I will be in the UK once again. BTW. Is backfocus adjustment on the stock lens done by any authorized Canon service center or it has to go to the factory or what? Please guys, share your knowledge and experience. Thanks for reading and sorry for such long and boring post... Piotr

January 11th, 2008, 10:04 AM	#243
Ryan Mueller Major Player Join Date: Mar 2007 Location: Highlands Ranch, CO Posts: 336	Hi Piotr, I think the reason that you are not getting any response on this is due to the fact that this issue has been covered extensively in the past. If you do a search for XL2 backfocus, you should be able to find plenty of information on your topic. I will tell you this though, the stock 20x XL2 lens has been known to be shipped with backfocus issues. Judging by your description, you have a backfocus issue that needs to be resolved through Canon. Good Luck! Ryan

January 12th, 2008, 04:49 AM	#244
Piotr Zubik Regular Crew Join Date: Jan 2008 Location: Miedzyrzec Podlaski, POLAND Posts: 30	Thank you Ryan for your reply! These are not good news for my XL2 but I'm glad I know what the problem may be. BTW. Yeah, I know it's been covered many times before, but as I wrote my problem is a little bit different (very small difference, seen mostly at f 1.6) and I did not find the definite answer in other topics as everybody had huge backfocus issue, everything blurred, only one guy mentioned about f stops,which still only similar to my problem.... Sorry for bringing out this already discussed topic. Anyway, as you said, I think I will have to take my camera to Canon... Thanks once again for your help.

January 12th, 2008, 10:04 AM	#245
Ryan Mueller Major Player Join Date: Mar 2007 Location: Highlands Ranch, CO Posts: 336	What you are experiencing with the f-stop difference is typical of all lenses, the higher the f-stop; the more that will be in focus. The lower the f-stop; less will be in focus therefore giving you a very shallow depth of field. For instance: you are shooting an interview with a person 6 feet away from the background, at an f-stop of 1.6 the subject will be in focus and the background will be slightly out of focus while at an f-stop of 5.6 the subject will be in focus while the background is more likely to be in focus as well. The bottom line is: if you zoom in and get critical focus then zoom back out and the focal point changes, you have a backfocus issue. This is true for any f-stop (especially a lower f-stop). Hope this helps, Ryan

January 12th, 2008, 12:44 PM	#246
Piotr Zubik Regular Crew Join Date: Jan 2008 Location: Miedzyrzec Podlaski, POLAND Posts: 30	Thank you Ryan for a detailed response. I know what DOF is and how to achieve it via iris adjustment, but frankly speaking I didn't know how it is related to backfocus issue at full wide shot. "The bottom line is: if you zoom in and get critical focus then zoom back out and the focal point changes, you have a backfocus issue. This is true for any f-stop (especially a lower f-stop)." This is 100% what I needed to know! Thanks, Piotr

January 12th, 2008, 01:21 PM	#247
Greg Boston Wrangler Join Date: Oct 2003 Location: DFW area, TX Posts: 6,117 Images: 1	Piotr, Also be advised that the stock 20x lens will close the iris down a couple stops as yo go full telephoto. The 16x manual lens is nice in this regard since it has manual back focus adjustment and will hold iris full open at the telephoto end. If you plan to keep the XL2 for awhile, the manual lens is a great investment IMHO. Enjoy your new camera! -gb-

February 1st, 2008, 05:52 AM	#248
Piotr Zubik Regular Crew Join Date: Jan 2008 Location: Miedzyrzec Podlaski, POLAND Posts: 30	UPDATE: I have just called my closest authorized service center. The lady on the phone gave me the price for backfocus adjustment (quite high) and told me that THE TECHNICIAN SAID THAT SOME XL2s CAN'T HAVE BACKFOCUS ADJUSTED PROPERLY DUE TO A "BUG" IN THIS MODEL. Have you ever heard of such thing? Can I get stuck with the lens that can't be fixed and the only solution to get rid of this tiny backfocus issue would be purchasing new stock 20x? The more i'm into this the more I'm considering Greg's advice on buying canon 16x full manual lens (still beyond my financial capabilities)

February 22nd, 2008, 02:56 PM	#249
Jonathan Kirsch Major Player Join Date: Jul 2006 Location: Denver, Colorado Posts: 204	Pioter, Did the person you talk to say how to find out if you have the model with the 'bug' in it? I'd like to know if mine is one of those models. I'm thinking my backfocus issus is...back. Jonathan

February 23rd, 2008, 11:51 AM	#250
Piotr Zubik Regular Crew Join Date: Jan 2008 Location: Miedzyrzec Podlaski, POLAND Posts: 30	Jonathan, I didn't spoke directly to the technician, only the receptionist who asked somebody in the background so she might have simplfied some stuff. However, when I emailed another canon service center they didn't tell me there's a bug or whatever, they just said that the price will depend on if it is only lens that need adjusting or lens and the camera body. Coud this mean the guys at previous center were wrong or just couldn't fix some XL2 backfouses int the past so they made up some BUG excuse? (that center though being authorized by Canon, are repairing several brands as well so maybe that's the reason) In two or three weeks I will be taking my XL2 to the second service center to solve backfocus AND some excessive noise (not dependent on gain custom settings) which I think I'm getting in light and dark places almost equally. It is not far away so I hope I will have the chance to speak to someone about this BUG and other issues. I must admit that after initial 'love' with the XL2 (when everything seemed extremely perfect because I did not have the chance to inspect everything properly) I'm somewhat depressed - first backfocus, then this alleged noise that I noticed and THEN you are saying that your backfous problem is BACK meaning that once repaired it may need to be done again. This is really bad providing backfous is quite pricey to fix :( Anyway, I will keep you informed. Piotr