# Canon 600mm mk2. Hard to "refocus" on different distances. Help/advice needed.



## Morlin (Feb 23, 2015)

Hi. 

I really love the results from my 600mm mk2 together with my 5D mk3 BUT I find it very hard to focus with. Like yesterday for an example. The main target was about 30m away. I had the setting on "16m and further away" because there would be no objects closer than that. But when I try to focus on the trees in the background that was about 200m further away it had big issues to find focus even though I think that the background had some contrast. I needed to use manual focus first and then it did focus properly on that distance. When I then wanted to set the focus again on the subject 30m away from me I again needed to use manual focus first. I tried several solutions by using more or less autofocuspoints and change the settings in the camera but I feel that the lens or the camera is struggling more than I expected. I have no friends with a lens like mine so I have no one to ask or compare to. Maybe the camera and lens is no better than so and that is what to expect but I find that hard to believe. Trying to catch flying birds is also really hard because I often need to focus manually first to somewhere close to the distance of the bird and then I can use autofocus. Can someone with own experience write about how it works for you? The examples are many when I have had a hard time getting the object in focus. 

Thanks.


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## NancyP (Feb 23, 2015)

Study your 5D3 manual section on autofocus. 

Typically I shoot BIF with center single-point AI servo. 60D, EF 400 f/5.6L. The center point is the only cross-point of the 9 points, so it is the best (most sensitive) point. I don't know the 5D3 AF system, you may have a cluster of center points to choose from. 

My gear is speedy and pretty accurate, and quite low-tech compared with your gear. Yes, I help it along, by using the AF limiter switch and by "pre-focusing" (manually if need be) if I know the approximate distance I will be shooting at. If the bird is going to come to a nearby small pond, I pre-focus on the pond, not the horizon. If I expect the bird to pass 50 meters away and there isn't a good target at 50 meters, I prefocus manually at 50 meters. 

The actual autofocus area is larger than the box in your viewfinder. If you are technically minded, go to clarkvision.com (or org, I forget), he has a good article on how autofocus works. It isn't magic, and it does have some inherent weaknesses. One of the weaknesses is that AF will acquire a strongly contrasty item at the edge of the single AF point coverage rather than a low contrast item dead center in the single AF point.
If you shoot handheld, that takes a lot of practice in acquiring your target and panning (yes, it is like hunting). Practice on anything that moves. Shooting with a gimbal mount also takes practice.


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## Mt Spokane Photography (Feb 23, 2015)

I'd also recommend trying different focus point options in your 5D MK III. For example, using the reduced center point can make low contrast objects difficult to focus on, but enabling surrounding points will help with this.


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## takesome1 (Feb 23, 2015)

Read the manual and use the AF preset on the lens. That helps.

I bought a 7D II when it was released. My 500mm F/4 II takes about 1.5 seconds to refocus when racked on the opposite end. With the 1D IV attached it takes half that long, about .7. So body does matter. The 7D II hunts more than the 1D IV.

Battery strength might matter to. Do you have other batteries to compare?

Your example, focusing at 30m then going to 200m. Remember the lens has to pick up on something. If it is a tree line and you are at f/4 and focused close you are asking the lens to focus on something that appears to be bokeh. This can happen with BIF, the sky is so OOF that the lens isn't picking any contrast and it hunts till it finds contrast.

On Page 99 of the 5D III manual.
Try both settings on AF4, Lens drive with AF impossible

I use the ON setting. The manual recommends the OFF setting.
Whichever you have been using, try the other.


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## Morlin (Feb 23, 2015)

Thank you for your answers. 

I have tried several autofocus points and have also tried both lens drive settings. The best result was with lens drive off because it hunted like crazy when I changed to on. Extremely quick though but hunted like a maniac. 

The batteries are ok. My 70-200 would not have had any issues at all in many of the situations where I found the 600mm struggling. 

I know that the autofocus need some contrast to be spot on but even in situations shooting at the same distance it can have issues. I tried yesterday on a dead fox laying on a rock and switched between focusing on the fox and a small bush at the side of the fox. The difference in distance was only a few meters to the targets and the sun was shining so there was a lot of details and contrast. 

I asked the same question in another forum and a guy with the exact same issue replied. Ha has the Canon 500mm mk2 and a 1D X and needs to help the lens out sometimes by manual focus to the correct distance before it can handle it. He have the same issue with 100mm macro and when I think about it I might also noticed about the same issue with my 100mm macro as well.

I will do some real testing but it sadly feels like there might be some kind of issue with the lens or the body. Maybe the combined duo. It´s hard when I have no chance to compare with another 600 or at least a 500mm. Maybe it is as good as it gets but I doubt it is.


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## neuroanatomist (Feb 23, 2015)

I have the 600 II and a 1D X. I've never had to 'help' the AF by prefocusing manually, and I haven't experienced hunting with the bare lens (although with complex subjects like a small bird in a thicket, it does hunt with the 2xIII attached – it behaves a lot like the 100-400 MkI in that way).


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## luckydude (Feb 24, 2015)

I have both the 7DII and the 5DIII and this lens.

I've had problems with it hunting on the 5DIII but I'm not yet sure if it is my technique or not.

Focus is fast on the 7DII but I'm getting soft images most of the time. I can't match anything like
the sharpness of this image (7DII, 400mm DO mark I, 1.4x III, hand held):

http://www.mcvoy.com/lm/wren.jpg

Did you 600mm owners have to do the front/back focus adjust with that lens (I've never done it with any lens, I typically get good results without it).

I get better results using live view, this was live view (so the mirror was locked up):

http://www.mcvoy.com/lm/moon.jpg

If I tried to take that same pic without the mirror locked up I got nothing but blur.

So far, this lens is pretty frustrating for me, I get good results with the 400mm & 1.4x (which is 560mm)
hand held; I can't match those results tripod mounted. I use a gitzmo and a gimbel (knockoff of the
good one, wimberly I think?). I'd love to be told how to use this lens, so far I'm sucking.


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## Mt Spokane Photography (Feb 24, 2015)

luckydude said:


> I have both the 7DII and the 5DIII and this lens.
> 
> I've had problems with it hunting on the 5DIII but I'm not yet sure if it is my technique or not.
> 
> ...



If live view gives sharper images, you very likely need AFMA. I AFMA all of my lenses as soon as I receive them. Its a good way to determine if there are any issues.

I had the original EF 600mm L, and AF was fast on any camera body, and I do not recall issues hunting for focus.


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## East Wind Photography (Feb 24, 2015)

Morlin said:


> Hi.
> 
> I really love the results from my 600mm mk2 together with my 5D mk3 BUT I find it very hard to focus with. Like yesterday for an example. The main target was about 30m away. I had the setting on "16m and further away" because there would be no objects closer than that. But when I try to focus on the trees in the background that was about 200m further away it had big issues to find focus even though I think that the background had some contrast. I needed to use manual focus first and then it did focus properly on that distance. When I then wanted to set the focus again on the subject 30m away from me I again needed to use manual focus first. I tried several solutions by using more or less autofocuspoints and change the settings in the camera but I feel that the lens or the camera is struggling more than I expected. I have no friends with a lens like mine so I have no one to ask or compare to. Maybe the camera and lens is no better than so and that is what to expect but I find that hard to believe. Trying to catch flying birds is also really hard because I often need to focus manually first to somewhere close to the distance of the bird and then I can use autofocus. Can someone with own experience write about how it works for you? The examples are many when I have had a hard time getting the object in focus.
> 
> Thanks.



There is a setting in the 5DIII firmware to only use cross type AF points. That helped considerably.


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## TeT (Feb 24, 2015)

you need to test your lens thoroughly in a controlled situation. Start with a AFMA and then test it focus Point by foucus point, array by array. Near to Far, far to near and beyond... No birds no moving targets. If you still feel its quirky, test it on a different body. If it still feels quirky then get it checked out (under warranty?)...


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## takesome1 (Feb 24, 2015)

luckydude said:


> I have both the 7DII and the 5DIII and this lens.
> 
> I've had problems with it hunting on the 5DIII but I'm not yet sure if it is my technique or not.
> 
> ...



I don't have the 600mm but I have the 500mm II, the same should apply.

I have a 7D II, the AFMA is +4 t o +6 on the 500mm, all my other bodies are right at 0 on the lens. I bet it is your camera not your lens. You need to check it. While the 7D II has some issues, you still should be getting a fair amount of really sharp pictures. 

Also for hunting, and this applies to the OP as well, if you are shooting in AI Servo then it may be a setting issue. Switch to Single Shot / Single Point and see if your lens is hunting. If it doesn't hunt in Single Shot mode maybe it is the sensitivity of one of your settings in AI Servo.


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## cervantes (Feb 24, 2015)

I use the 500II on a 5D3 and can't remember having said issues.

I did however create a quite extensive article about the 5D3 AF system that also covers the topic of how to change focus distances quickly while using super telephoto lenses.

You can find the article here: http://www.focrates.com/articles/configuring_your_5d_mark_3_af_for_fast_action/configuring_your_5d_mark_3_af_for_fast_action.html

Greetings!


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