Focus problem with 600 mm IS 2 plus 1.4 and 2.0 TC's

[Carlosbuddie]

I have focus problem with my newly acquired 600mm IS series 2 canon lens.

I have a 60d, a 7d mk2 and a 5d mk3The lens works well on all three cameras, if I couple it up to a 1.4   iii or 2.0 iii  tc, the focus goes to pot (see image, AF point bang in the middle of the birds back.) The bird was approx. 200 ft away.

If I couple it up to the 1.4 on my 60d I get  fantastic images even at about 2KM distance.

Any one had any similar problems. I would be grateful for any info. Thanks in advance.

[Carlosbuddie]

[Waddizzle]

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@Carlosbuddie wrote:

I have focus problem with my newly acquired 600mm IS series 2 canon lens.

I have a 60d, a 7d mk2 and a 5d mk3The lens works well on all three cameras, if I couple it up to a 1.4   iii or 2.0 iii  tc, the focus goes to pot (see image, AF point bang in the middle of the birds back.) The bird was approx. 200 ft away.

If I couple it up to the 1.4 on my 60d I get  fantastic images even at about 2KM distance.

Any one had any similar problems. I would be grateful for any info. Thanks in advance.

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First you say it doesn't work with a telecovnverter, and then you say it does work.  Problem solved.  BTW, what brand of TC?

What is the f/stop of your lens?  That is the most significant specification that determines how well a given lens might work with a given combination of lens and body.  A teleconverter raises the effective minimum f/stop of lens.  A 1.4 converter rail rise the minimum f/stop by one full stop, and a 2.0 converter will raise the minimum f/stop by two full stops.  

The increase in f/stop is the price that you pay for the increase in effective focal length.  Every AF sensor has photo sensors that require a certain minimum amount of light to function accurately and consistently.  In other words, if the minimum aperture of a lens is too high, then the camera firmware will disable the AF system, when you focus through the viewfinder.  Live View uses a different focus system.

Most Canon DSLRs cannot consistently and accurately focus with a lens that has a minimum effective aperture smaller than f/5.6.  Your 60D falls into this category.  Canon's professional grade cameras have sensors that focus down to f/8, but this ability is limited to just the center focus point. 

When you used the teleconverter, you may have noticed a change in the number of available AF points.  With the 7D and 5D camera bodies, you should have only been able to use just the center point in AI Servo mode.  In One Shot mode, depending upon your settings, you should be able to get the center and a few surrounding points, but only the center locks focus.  With the 60D, the camera should not have been able to AF though the viewfinder, at all.

There is nothing that I saying is secret knowledge.  All of it is in the documentation of your gear.  

[Carlosbuddie]

Thanks for your reply but I think you have misread my post.

 I said the lens works on all 3 bodies until I attach the tc's, Which by the way are both Canon  series 3.

 When I attach the tc's to the 7d and the 5d   although the image in the viewfinder is clear, the actual  image in the camera  is out of focus. Incidfentally  using manual focus makes no difference.

 When I attach the 1.4 tc to my 60 d everything works perfectly, obviously the 2x tc will not focus as the minimum aperture is to big.

 The lens as I am sure you know is  minimum aperture of  f4, therefore the 60d will AF

[Waddizzle]

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@Carlosbuddie wrote:

Thanks for your reply but I think you have misread my post.

 I said the lens works on all 3 bodies until I attach the tc's, Which by the way are both Canon  series 3.

 When I attach the tc's to the 7d and the 5d   although the image in the viewfinder is clear, the actual  image in the camera  is out of focus. Incidfentally  using manual focus makes no difference.

 When I attach the 1.4 tc to my 60 d everything works perfectly, obviously the 2x tc will not focus as the minimum aperture is to big.

 The lens as I am sure you know is  minimum aperture of  f4, therefore the 60d will AF

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"I have a 60d, a 7d mk2 and a 5d mk3The lens works well on all three cameras, if I couple it up to a 1.4   iii or 2.0 iii  tc, the focus goes to pot."

"If I couple it up to the 1.4 on my 60d I get  fantastic images even at about 2KM distance."

Nope, I didn't misread your post.  At first it didn't work with the 60D.  Now?  It works great with you 60D.  But, it should work with all of the camera bodies, though.

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Comparinng the image in the viewfinder to "the actual image in the camera" can be misleading because of the diopter.  Is it in focus in Llive View?  In fact, all of the cameras should be able to focus in Live View mode, even if the effective minimum aperture is over f/8.

It could be some combination of AF settings and initial AF point selection in the newer bodies.  Make sure you always start with the center AF point, especially with the 2.0x extender.  Make sure that you have the latest firmware.  Check to see if it works in Green [A] mode, too.  

If it still doesn't work with the newer bodies, then contact Canon Support.  

[Mr_Fusion]

I have two guesses and a point here.

1) Camera shake. Either your tripod isn't strong enough to hold that weight. Also, a lens that size will catch a lot of wind. Remember, with a lens that long, any movement is amplified a heck of a lot.

Use the most robust tripod you can buy. You are using a serious, heavy duty lens, use a serious, heavy duty tripod. 

Second would be to also use a remote shutter. That way you aren't even breathing on the camera when you take the picture. 

2) Atmospheric disturbance. This is a real problem in long range sharp shooting. As the sun heats the ground, the air rises, causing a shimmering effect. Moisture in the air can also cause disturbances. While we can see this happen over long distances of flat terrain, it also happens over undulating and shorter terrain too.

In the viewfinder trhe image appears clear and in focus because our eyes compensate for minor deviations. The shot though, captures a view faster than our eyes would notice. 

3) Have you tried those teleconverters on shorter lenses, say a 200? That would tell you how much distortion they bring to the issue. We know they will bring some distorsion, the question is how much.

As I said, I'm guessing, but I would be interested in any other explanation.

[ebiggs1]

You have this lens, Canon EF 600mm f/4L IS II USM Lens?   A $12,000 dollar lens.    I have one and I am probably the only regular here that has ever used one.  Mine is the first version.

All your cameras except the 6D should AF with either a 1.4x or 2x t-con.  However, just because it will does not mean much because there is so much more to using a focal length of 1200mm at f8.

"I get  fantastic images even at about 2KM distance."

I am guessing '2km' means 2 kilometers?  OK, at that distance you add an additional problem.  The atmosphere.  That's right just the air itself causes issues.  A big misconception about super teles is they were designed to photograph things a long ways away.  Yeah they will but actually they shine at filling the shot with tiny subjects at much closer distances.  A small bird for example at 25 to 30 feet. Or, perhaps the face of a baseball or football player.  100 yards or less.

My best advice for you is two things.  One, get closer, get much closer.  Two, get a real beefy tripod.  1200mm at f8 is not a hand hold lens.

Oh, yeah, one more thing forget using the 2x t-con all together.  Even better stop using the 1.4x too!

[Carlosbuddie]

Thank you for your reply

I mentioned the 2KM  image because I can't understand why a 6 year old 60d with 600m  lens and 1.4 converter wil focus perfectly at that didtsnce but  a 7d mk2 and 5dmk3 both less than a year old, cannot focus with either of the converters at a distance of 200 ft. Incidentally A  Tripod was used on all shots plus IS was switched on.

 I understand also about the atmospheric distortion, we have temperatures regularly 35 -40 c. I wouldn't normally use the lens for anything at that distance I  just wanted to see how  all the cameras and lens +tc's    performed  taking the same shot. The 60d wasthe only on that could give me an acceptable result.

[RobertTheFat]

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@Carlosbuddie wrote:

Thank you for your reply

I mentioned the 2KM  image because I can't understand why a 6 year old 60d with 600m  lens and 1.4 converter wil focus perfectly at that didtsnce but  a 7d mk2 and 5dmk3 both less than a year old, cannot focus with either of the converters at a distance of 200 ft. Incidentally A  Tripod was used on all shots plus IS was switched on.

 I understand also about the atmospheric distortion, we have temperatures regularly 35 -40 c. I wouldn't normally use the lens for anything at that distance I  just wanted to see how  all the cameras and lens +tc's    performed  taking the same shot. The 60d wasthe only on that could give me an acceptable result.

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Given the reported symptoms, the first thing I'd do is see if the lens needs autofocus microadjustment on the 5D3 and the 7D2. I've yet to encounter an "L" lens that needed AFMA on any of my cameras; but with a lens that long and a TC added, you're arguably putting some major stress on the cameras' AF systems. If that turned out to be the problem, you'd be in luck, because the 60D is the only one of your cameras that doesn't have AFMA.

Another thing you might try is to turn off IS. Some people claim that IS can do more harm than good when the camera's on a tripod. I don't know whether it's true, but the experiment can't do any harm.

[Carlosbuddie]

Hi Bob,

 Tried all that, I have tried just about any and every combintaion of  anything I could think of  all to no avail. 😞