Canon KH20x6.4 on EX3

Nathan Lawrence · October 5th, 2012, 09:06 PM

I just purchased a used Canon KH20x6.4 lens for my EX3 - primarily for the extra zoom.

I noticed that when I adjust the focus wheel, the image zooms in or out noticeably. I don't notice this AT ALL with the stock lens. Is such behavior normal/expected on this lens or is there something wrong? My purchase has a 30-day warranty, so I can presumably get it resolved, if it is an issue.

Thanks!

Nathan Lawrence
AudioART

Luc De Wandel · October 6th, 2012, 01:52 AM

Zooming in and out when focusing is called 'breathing' and is a know phenomenon in lenses of poor design. It proves how good the stock lens is, and it also proves that the Canon lens, however sharp and ergonomically superior to the stock lens, is optically not the best there is. On the other hand, some other Canon HD-lenses, like the wide-angled KH 10E x 3.6 IRSE that I have on my PMW320 show much less breathing. It's all a matter of price, I suppose...

Alister Chapman · October 6th, 2012, 06:26 AM

The difference is that the KH20 is a traditional mechanically focussed lens that uses the front element groups to focus while the stock EX3 lens is electronically focused via the middle and rear lens elements.

Traditional lenses almost always exhibit some breathing as you focus, some more than others because moving the front elements forwards and backwards slightly alters the focal length. Longer focal length lenses and high ratio zooms tend to exhibit the most breathing. However when you use the middle and rear elements under electronic control the focal length doesn't change as you focus. The stock EX lens is actually of a much simpler design than the KH20. This is possible because as you zoom an electronic look up table is used to add focus corrections, eliminating the need to construct a mechanically sophisticated design that uses cams and moving correcting lenses to make the lens par focal.

Nathan Lawrence · October 6th, 2012, 09:02 AM

Thanks very much to both of you for your helpful comments.

For what I bought this lens for, I don't think this breathing will be too much of an issue for me to work around.

A further question: Is this something that is constant from lens to lens of the same model, or do some of them come out better than others? Is it something that remains constant on the lens, or does it possibly increase as a lens gets older and parts get worn at all? (You can see, I don't know a whole lot about lenses!)-- I have not seen much mention of this lens and 'breathing' in other posts, so I just want to make sure that there are no issues that I should use the warranty for. Obviously you may be somewhat limited in your response without actually seeing the lens in action.

Thanks again for the input!

Alister Chapman · October 6th, 2012, 09:24 AM

Breathing will be the same for all KH20's and it shouldn't change with age or wear and tear. It's just the way the lens is designed. I used to have a KH20 on my old PDW-350 and then EX3. It's an OK lens, not great, but OK. I also had a YH19x6.7 which is an SD lens, cost a lot less, but performed almost exactly the same as the KH20.

The other thing you'll notice is more chromatic aberration (purple/blue fringing) with the KH20 because when you use the standard lens the camera uses an electronic aberration reduction process that you don't get with other lenses.

Nathan Lawrence · October 6th, 2012, 09:29 AM

Thanks so much! Now I can just go and enjoy my lens without worry.

Nathan Lawrence
AudioART

Luc De Wandel · October 6th, 2012, 11:12 AM

As Alister says, breathing will be the same for all KH20's, but sharpness may differ. Years ago, I worked in a photo shop and had a chance to take several lenses home with me for extended testing. It turned out that there were noticeable differences in sharpness and contrast between lenses of the same make and type. Probably due to the quality of the glass itself. So I suppose this will be the same for video lenses as well.

I also use the YH19x6.7 KRS on my PMW320 and I see practically no difference in sharpness with the KH10 x 3.6 IRSE, that costs about 8 times as much... Both are very sharp. I'm sure there will be a measurable difference in resolution, but not one I can see with the naked eye, not even on a 42 inch screen.

Nathan Lawrence · October 6th, 2012, 08:57 PM

Luc,

Again, excellent information to know about. I'm very happy so far with the sharpness of my Kh20 -- so either I have good glass or bad eyes (probably a little of both).

Now if only this lens had image stabilization.... Well, I guess I just need to move up past my 503 head system (Sachtler, Miller....)

Thanks again for all of your help.

October 5th, 2012, 09:06 PM	#1
Nathan Lawrence Regular Crew Join Date: Feb 2008 Location: Cobleskill, NY Posts: 51	Canon KH20x6.4 on EX3 - issues? I just purchased a used Canon KH20x6.4 lens for my EX3 - primarily for the extra zoom. I noticed that when I adjust the focus wheel, the image zooms in or out noticeably. I don't notice this AT ALL with the stock lens. Is such behavior normal/expected on this lens or is there something wrong? My purchase has a 30-day warranty, so I can presumably get it resolved, if it is an issue. Thanks! Nathan Lawrence AudioART

October 6th, 2012, 01:52 AM	#2
Luc De Wandel Major Player Join Date: May 2008 Location: Knokke-Heist, Belgium Posts: 963	Re: Canon KH20x6.4 on EX3 - issues? Zooming in and out when focusing is called 'breathing' and is a know phenomenon in lenses of poor design. It proves how good the stock lens is, and it also proves that the Canon lens, however sharp and ergonomically superior to the stock lens, is optically not the best there is. On the other hand, some other Canon HD-lenses, like the wide-angled KH 10E x 3.6 IRSE that I have on my PMW320 show much less breathing. It's all a matter of price, I suppose...

October 6th, 2012, 06:26 AM	#3
Alister Chapman Inner Circle Join Date: Dec 2005 Location: Bracknell, Berkshire, UK Posts: 4,957	Re: Canon KH20x6.4 on EX3 - issues? The difference is that the KH20 is a traditional mechanically focussed lens that uses the front element groups to focus while the stock EX3 lens is electronically focused via the middle and rear lens elements. Traditional lenses almost always exhibit some breathing as you focus, some more than others because moving the front elements forwards and backwards slightly alters the focal length. Longer focal length lenses and high ratio zooms tend to exhibit the most breathing. However when you use the middle and rear elements under electronic control the focal length doesn't change as you focus. The stock EX lens is actually of a much simpler design than the KH20. This is possible because as you zoom an electronic look up table is used to add focus corrections, eliminating the need to construct a mechanically sophisticated design that uses cams and moving correcting lenses to make the lens par focal. __________________ Alister Chapman, Film-Maker/Stormchaser http://www.xdcam-user.com/alisters-blog/ My XDCAM site and blog. http://www.hurricane-rig.com

October 6th, 2012, 09:02 AM	#4
Nathan Lawrence Regular Crew Join Date: Feb 2008 Location: Cobleskill, NY Posts: 51	Re: Canon KH20x6.4 on EX3 - issues? Thanks very much to both of you for your helpful comments. For what I bought this lens for, I don't think this breathing will be too much of an issue for me to work around. A further question: Is this something that is constant from lens to lens of the same model, or do some of them come out better than others? Is it something that remains constant on the lens, or does it possibly increase as a lens gets older and parts get worn at all? (You can see, I don't know a whole lot about lenses!)-- I have not seen much mention of this lens and 'breathing' in other posts, so I just want to make sure that there are no issues that I should use the warranty for. Obviously you may be somewhat limited in your response without actually seeing the lens in action. Thanks again for the input!

October 6th, 2012, 09:24 AM	#5
Alister Chapman Inner Circle Join Date: Dec 2005 Location: Bracknell, Berkshire, UK Posts: 4,957	Re: Canon KH20x6.4 on EX3 - issues? Breathing will be the same for all KH20's and it shouldn't change with age or wear and tear. It's just the way the lens is designed. I used to have a KH20 on my old PDW-350 and then EX3. It's an OK lens, not great, but OK. I also had a YH19x6.7 which is an SD lens, cost a lot less, but performed almost exactly the same as the KH20. The other thing you'll notice is more chromatic aberration (purple/blue fringing) with the KH20 because when you use the standard lens the camera uses an electronic aberration reduction process that you don't get with other lenses. __________________ Alister Chapman, Film-Maker/Stormchaser http://www.xdcam-user.com/alisters-blog/ My XDCAM site and blog. http://www.hurricane-rig.com

October 6th, 2012, 09:29 AM	#6
Nathan Lawrence Regular Crew Join Date: Feb 2008 Location: Cobleskill, NY Posts: 51	Re: Canon KH20x6.4 on EX3 - issues? Thanks so much! Now I can just go and enjoy my lens without worry. Nathan Lawrence AudioART

October 6th, 2012, 11:12 AM	#7
Luc De Wandel Major Player Join Date: May 2008 Location: Knokke-Heist, Belgium Posts: 963	Re: Canon KH20x6.4 on EX3 - issues? As Alister says, breathing will be the same for all KH20's, but sharpness may differ. Years ago, I worked in a photo shop and had a chance to take several lenses home with me for extended testing. It turned out that there were noticeable differences in sharpness and contrast between lenses of the same make and type. Probably due to the quality of the glass itself. So I suppose this will be the same for video lenses as well. I also use the YH19x6.7 KRS on my PMW320 and I see practically no difference in sharpness with the KH10 x 3.6 IRSE, that costs about 8 times as much... Both are very sharp. I'm sure there will be a measurable difference in resolution, but not one I can see with the naked eye, not even on a 42 inch screen.

October 6th, 2012, 08:57 PM	#8
Nathan Lawrence Regular Crew Join Date: Feb 2008 Location: Cobleskill, NY Posts: 51	Re: Canon KH20x6.4 on EX3 - issues? Luc, Again, excellent information to know about. I'm very happy so far with the sharpness of my Kh20 -- so either I have good glass or bad eyes (probably a little of both). Now if only this lens had image stabilization.... Well, I guess I just need to move up past my 503 head system (Sachtler, Miller....) Thanks again for all of your help.