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Occasional Contributor
Posts: 11
Registered: ‎09-10-2017

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

Hi Bob,

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

VIP
Posts: 8,119
Registered: ‎12-07-2012

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

The obvious question, does the lens/camera combo work as expected with out the t-cons? Remember you are getting simple photographic logic when you ask people that have never used a lens in this category.  I know my lens works very well on a 7D and 1D Mk IV and Ds Mk III.  But I don't use any t-cons.  BTW, what brand T-con are you tying to use?

 

A lens of this type can benefit form a C&C from time ot time.  Send it to Canon for a C&C and they will go over it completely. Lenses in this range are unto themselves.  They are not and do not act like the more common and used standard lenses.

 

My Sigma 150-600mm S works well at 600mm on these cameras, too.

 

Most likely the reason your 6D focuses at 2KM is the DOF is huge at that distance.  So, if it missed by 10 or 20 feet, no biggie.

A lot of Canon stuff. Along with, a lot of other stuff.
Esteemed Contributor
Posts: 3,082
Registered: ‎06-11-2013

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

[ Edited ]

Whenever you question the accuracy of camera & lens focus, you really can't come to any conclusions unless you do what I'd consider to be somewhat scientifically valid testing procedures.

 

In other words you have to think of all the things that can go wrong which would be attributed to factors OTHER than the camera & lens.

 

1)  Was the camera on a SOLID tripod?  I did read that you had a tripod... but was it a beefy tripod?

2)  Was it windy?

3)  What was the shutter speed?  Did you use mirror lock-up mode?

4)  Was the subject moving?

5)  Did you use a remote release or self-timer to take the shot?

6)  Was it hot (at a distance of 2km, thermals radiating off of hot earth will distort the image.)?

 

We could come up with more reasons... these are just a few examples.

 

You might want to do some testing where you can control these conditions... I would encourage you to use an actual focus-accuracy target such as a "LensAlign" or "LensCal".  These tools offer a high-contrast target on a flat card.... but that's adjacent to a sloped scale with high-contrast on it as well.  The idea is you focus on the target but then check the sloped scale to see if some point along that scale has better focus than the target (it tells you if your camera & lens are front-focusing or back-focusing.)

 

The fact that the 60D is able to achieve a nice image says that there's nothing wrong with the "optics" per se.  But your 7D II or 5D III might need to do an auto-focus micro-adjust (and you want a test target to work that out.)

 

It's actually encouraging to hear that the 60D is doing well with the lens & teleconverter combo because it suggests that the lens doesn't need service.  We just need to work out why you're not getting similar good results with your 7D II or 5D III.

 

What's interesting is that the 60D is the only xxD series body that does NOT support auto-focus micro-adjustments (AFMA) and that's the one that you're happy with.  The other cameras that you aren't happy with are the ones that let you adjust the focus.

 

When the phase-detect auto-focus system is working, light enters the camera, bounces off the secondary mirror and down into the focus sensors.  The sensors have a beam-splitter (a prism) that splits the light into two paths that will exactly re-converge ONLY if the subject is in focus.  But if not focused they will be out-of-phase.  The computer can detect how far out-of-phase they area and in which direction.  It computes how much of a focus adjustment is required and then it moves to to the correct focus point.  The amount of focus adjustment is actually computed and the lens is ordered to focus.  The amount of adjustment will be different with just the lens alone vs. the lens coupled with a teleconverter (but the firmware knows this).  

 

If the camera isn't nailing the focus, you can use a test target to work out how much of a correction is needed and both the 7D II and 5D III will let you program in some amount of adjustment (the cameras can "remember" something like 50 unique lenses.  So the focus adjustment for THIS lens might not be the same as the focus adjustment for your other lenses.)

 

I'm not say that your camera & lens combo do need a focus adjustment (AFMA) ... but I am saying it's certainly a possibility (and maybe even a very strong possibility).  This is something you can do yourself -- no need to send the equipment to Canon for service.

 

When using a long, heavy camera lens to shoot moving subjects, you might want to consider a beefy tripod base with a gimbal head (the Wimberley gimbal heads are popular.  I own an Induro head which is basically the same as a Wimberley head).  The gimbal head allows you balance the the camera & lens such that it is neutrally balanced in all directions.  Because of this, you can point the camera anywhere and there's actually need to snug down the tripod head.  The camera will remain pointed where you put it.  This allows you to move the camera "like a tail-gunner" to capture any targets.  If you tried this with a ball-head or pan-head, you'd have to keep re-snugging the head.  

 

 

 

BTW, for many lenses, the image stabilization should be disabled if the lens is attached to a tripod.  This is because the snap motion to adjust the optics in the IS system can actually cause a vibration which is interally felt (when on a tripod) and the lens will attempt to react to it's own vibration.  It results in a feedback loop.   But newer lenses (and I think the 600 is new enough) can detect when this is happening.  For those newer lenses you can leave the IS on.

 

If the 60D can get a sharp image then it's possible to get a sharp image with the other cameras.  The lens is basically like a movie projector attemping to shine an image on a movie screen.  If it can be sharp on the 60D then it can be sharp on the others as well.

 

You can only trust manual focus via the viewfinder if you've adjusted your viewfinder for your own eyes.  To do this, deliberately de-focus the lens and point it at a plain white wall (or plain blue sky - but not near the sun).  Carefully adjust the diopter wheel (on the corner of the viewfinder) until the viewfinder graphics are as sharp as possible.  

 

The camera is basically projecting an image onto the viewfinder's focus screen.  It's the frosted "glass" you see above the mirror in your camera.  When you look through the viewfinder, you are inspecting the image on that focus screen.  But depending on your eyes, whether or not you use glasses, etc. that screen may not be in perfect focus to YOUR eyes even if the image on the screen is perfectly sharp.  The diopter adjustment wheel allows you to adjust for that to compensate for your eyes.   Once the graphics you can see on the focus screen (focus points, grid lines, etc.) are perfectly sharp you can now trust manual focus.

 

Tim Campbell
5D III, 5D IV, 60Da
VIP
Posts: 8,119
Registered: ‎12-07-2012

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

About IS, my thoughts.

  1. Do not turn IS on unless working at shutter speeds lower than inverse of the focal length of the lens. It can hurt the sharpness a little.  (600mm = SS 1/600 or rounded to 1/1000)
  2. If you decide to turn IS on, make sure to half-press the shutter button for a second to let the camera/lens stabilize a little first. If you shoot right away without stabilizing, it will most likely negatively impact the sharpness of your images.

As to whether it hurts or helps when on a tripod, I don't know for sure.  I have tried to prove it both ways and am no convinced.

But I am using a really substantial tripod.  That can be the factor that makes the difference. Flimsy tripods are useless.

A lot of Canon stuff. Along with, a lot of other stuff.
Reputable Contributor
Posts: 859
Registered: ‎02-06-2013

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


Carlosbuddie wrote:

Hi Bob,

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


The only thing you haven't mentioned trying is check the option "Lens Drive When Focus Impossible" and make sure that it is set to continue to focus (can't remember if this is 0 or 1).  For whatever reasons the camera thinks focus is impossible (it is often wrong), it stops focusing.

 

I do have a 600mm f/4L lens that I use with the 7D2 and 5D3 and they work perfectly with both the 1.4 and 2.0 installed and the option set to continue to try to focus.  I discovered this option due to problem focusing with the option set to stop.

================================================
Diverhank's photos on Flickr
Occasional Contributor
Posts: 11
Registered: ‎09-10-2017

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

Thanks for your reply, thought you were onto something there but no luck still the same Smiley Sad

Occasional Contributor
Posts: 11
Registered: ‎09-10-2017

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

Thanks for your reply.

 Yes I had noticed that on mode 1 the IS seems to Hunt for a couple opf seconds before settling down. mode 2 seems to be a little quicker.

Occasional Contributor
Posts: 11
Registered: ‎09-10-2017

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

Thanks for you epic reply TCampbell. Smiley Happy

 You seem to have grasped what I was getting at, IE if it all works on an old 60d then it should work (better) on the 7dmk23 and the 5dmk3.

 Yes on a solid tripod.

Not windy.

Shutter speed  1/1000 to 1/1250 at f11 iso 400, no mirror lock up mode.

Subject not moving ( see image of Eagle in other post with same title)

Yes, remote release.

 Yes fairly hot about 30 c but same temp for all three  cameras.

I have tried micro adjusting the lens and converters, not with a chart but a stationary object and changing the - or + by a couple of segments at a time between images, but no difference.

 If you look at the image of Eagle in other post with same title you can see that the whole image is well out of focus front and back. The AF point was dead on his back at about 200 feet or between 50 m and Infinity, closer to infinity.

 Manual focus gives the same result, out of focus.

 The lens is brand new as are the converters (Canon)

Honored Contributor
Posts: 5,440
Registered: ‎08-13-2015

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

[ Edited ]

I think I asked before about what focus mode and AF points are you using.  

How do you have the options for continuous shooting?  Focus Priority or Shutter Priority?  I always set this all the way towards Focus Priority, because what is the point of taking a rapid sequence of shots if they are not in focus. 

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Esteemed Contributor
Posts: 3,082
Registered: ‎06-11-2013

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

It's a bit difficult to tell much from your eagle shot because the image is small when posted online (do you have a full-res image posted somewhere?)    

 

Anyway, you don't necessarily have to buy a commercial focus test target since the principle is fairlly simple.

 

Imagine having a flat high-contrast target.  

Now imagine laying a yard-stick / meter-stick on a slope so that the low end is nearest to the camera and the high end is farthest from the camera and the mid-point of the measuring stick is adjacent to your flat focus target.

 

Use single-point AF, select the center point, and focus on the test target (solidly on the test target - make sure there's no chance the AF point missed the intended target).

 

Now download the image and carefully inspect... not the target... the measuring stick adjacent to the target.  Since it was on a slope you should be able to see the enter stick from front to back.  You're looking to see if the some point along the stick appears to have better focus than the intended focus point.

 

Here's an example that I did with my EF 300mm f/2.8L IS USM (original).

 

The focus target should be at about 25x the focal length (for lenses longer than 200mm).  300mm x 25 = 7500mm.  That's 7.5 meters (24.6 feet).  

 

I measured out a 25' distance (close enough)

 

I needed to find a high-contrast target so I used a Lego model of a rocket.   I also grabbed a measuring scale (in my case a metal 60" scale).

 

I placed the scale adjacent to the rocket body so that my intended focus point (I pick a bold high-contrast point where the black & white meet) were at the 30" mark (and later discovered it was in fact nearer to 29.5" and not my intended 30")

 

Camera is on a tripod using the f/2.8 focal ratio (shallowest depth of field available for this lens)

 

I turned off image stabilization and deliberately de-focused the lens (to force it to focus) and took a few shots.  Here's a sample:

 

Focus Test (full image).JPG

 

It's a bit difficult to read the scale without cropping in, so here's a cropped in section.

 

Focus Test (crop section).JPG

 

Remember that the point on the scale which is even with the front of the rocket body (the point I chose was the top of that black stripe).  

 

Now I inspect the scale.  I can see that the 27" mark is going a bit soft.  Likewise I can see the 32" mark is going a bit soft.  The 28 and 31 marks look a bit better.  The 29 and 30 marks both look equally good to my eyes.  And I also confirmed by walking up and re-inspecting the scale & target that it was, in fact, the 29.5" point where the rule was at the front of the rocket body (not the 30" mark that I intended... the scale slipped a bit after I laid in position).

 

In this case my lens nailed the focus bang-on accurate.

 

Anyway... you get the idea.  You don't necessarily need a commercial target if you set up a valid test.

 

Since you have a 600mm lens with a 2x teleconverter, that's 1200mm, the target should be about 30 meters from the camera body (quite a distance) - which is why I suggest using a larger scale rather than a commercial test target (which tends to be small).

 

 

Tim Campbell
5D III, 5D IV, 60Da
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