Canon AF and stacked 2x TCs with 1D bodies

[Roger Clark]

Hi,

I often image with stacked 2x and 1.4x TCs using 500 mm f/4, 300 f2.8, and 300 f/4 bodies. Sometimes I want more reach (on fixed subjects). At these magnifications, I find when I touch the lens to autofocus using live view, with IS on or not, the vibrations are too much to accurately focus, so I want autofocus. AF works fine with stacked 2+1.4x TC on 1D bodies.

So my question, has anyone stacked 2x TCs (I only have one Canon 2x)? Do you still get a good AF lock without overshoot? I will be using it with a 1D Mark IV. Last night I tried 2x canon + 1.4x Canon + 1.4x kenko pro 300 and focus just overshot. I could not get any AF lock. I was trying to focus on the Moon. Here is what I got with 2x+1.4x:
http://www.clarkvision.com/galleries/gallery.moon/web/moon_c09.18.2010_1d41400mm_e-900.html

Roger.

[Doug Brown]

Have you tried using a cable release in combination with Live View?

[Roger Clark]

Doug,

Yes. Last night I was photographing the Moon (it was National Observe the Moon Night):
http://www.clarkvision.com/galleries/gallery.moon/web/moon_c09.18.2010_1d41400mm_e-900.html

Even with a cable release, the 1DIV overshot with 3 stacked TCs.

Roger

[Charles Glatzer]

Roger,

You cannot stack two 2x converters without using an extension tube between them.
As far as I know there is no production camera made that will AF with stacked 2x converters.

Chas

[Arthur Morris]

By "overshot" do you mean that you could not get focus lock?

Are you trying to focus using Live View?

[Roger Clark]

By "overshot" do you mean that you could not get focus lock?

Are you trying to focus using Live View?

Artie,

With the 500 + 2x +1.4x +1.4x + 1DIV, the lens would move completely through the focus point and stop some where on the other side, way out of focus. I would half press the shutter button again and the lens would be moved the other way, all the way through focus and stop way on the other side. again way out of focus. I never could get focus lock.

So then I turned on live view. I can get close but at these magnifications, the the vibrations prevent seeing fine details, and the focus ring is too coarse to get the focus easily by hand. I could probably get a good focus but it might take 10 or 20 minutes. I also tried live view with IS on (and off). With IS on, I was hoping the small vibrations would be compensated so I could focus, but not.

Roger

[Roger Clark]

Roger,

You cannot stack two 2x converters without using an extension tube between them.
As far as I know there is no production camera made that will AF with stacked 2x converters.

Chas

Chas,
I'm do not see why you can not stack 2 canon 2x TCs without a spacer. The protrusion out the front and the hole in the rear seem the same as the 1.4x and one can stack the 2x and 1.4x TCs.

Roger

[Arthur Morris]

Artie, With the 500 + 2x +1.4x +1.4x + 1DIV, the lens would move completely through the focus point and stop some where on the other side, way out of focus. I would half press the shutter button again and the lens would be moved the other way, all the way through focus and stop way on the other side. again way out of focus. I never could get focus lock. So then I turned on live view. I can get close but at these magnifications, the the vibrations prevent seeing fine details, and the focus ring is too coarse to get the focus easily by hand. I could probably get a good focus but it might take 10 or 20 minutes. I also tried live view with IS on (and off). With IS on, I was hoping the small vibrations would be compensated so I could focus, but not. Roger

Thanks Roger. With this combo: With the 500 + 2x +1.4x +1.4x + 1DIV, no camera--pro body or otherwise--would be able to focus (without Live View) because the pro bodies are designed to focus only down to f/8. BTW, are you putting a 12mm tube between the 1.4 TC with this combo?)

My very strong suspicion is that that combo will not focus because of the relatively low contrast. Try it in bright sun with Live View on a subject with diagonal black and white lines and I think that it might focus.

[Arthur Morris]

Chas, I'm do not see why you can not stack 2 canon 2x TCs without a spacer. The protrusion out the front and the hole in the rear seem the same as the 1.4x and one can stack the 2x and 1.4x TCs. Roger

Roger, you are of course correct on this one.

[Arthur Morris]

Roger, You cannot stack two 2x converters without using an extension tube between them. As far as I know there is no production camera made that will AF with stacked 2x converters. Chas

Hi Chas, You can stack the relatively new EF 2X II TCs as they have a larger rear opening than the old 2X TCs. In fact, you could stack ten of them together if you wanted to.

You are correct about no camera being designed to focus with stacked 2X TCs during regular photography. When using Live View, however, the AF system will not only work with stacked 2X TCs (provided you have enough contrast), put you can move the focusing indicator to anywhere within the frame.

With respect.

[Roger Clark]

Thanks Roger. With this combo: With the 500 + 2x +1.4x +1.4x + 1DIV, no camera--pro body or otherwise--would be able to focus (without Live View) because the pro bodies are designed to focus only down to f/8. BTW, are you putting a 12mm tube between the 1.4 TC with this combo?)

Artie,

You are correct that the bodies are not designed to focus with slower than f/8 configurations. But when you stack TCs, only one TC gets reported to the camera. So the camera does not know there is more than one TC, and it tries to focus anyway. The problem is with stacked TCs, the phase detect system computes how much to move the focus and overshoots because the magnification of the second TC is not included in the calculation. With a stacked 2x and 1.4x TCs, there error is smaller and the system does pretty well in my experience.



My very strong suspicion is that that combo will not focus because of the relatively low contrast. Try it in bright sun with Live View on a subject with diagonal black and white lines and I think that it might focus.

The Moon, because it is illuminated by the sun, is similar in brightness to day scenes on Earth. The image I did the other night was 1/100 second at f/11.2. That is only 2 stops down from the sunny f/16 rule. Also, the Moon, with no atmosphere has almost completely black shadows, so is one of the highest contrast subjects one can image.

Late last night the clouds cleared so I dug out my old Kenko pro 300 2x TC and stacked it behind the canon 2x II TC and was able to get AF lock. I did have some problems with overshoot, but by manually moving focus to close to the right position and placing the center focus point on the edge of the moon, I did get focus lock:). I was able to record finer details than I could with the stacked 2+1.4x TCs. I expected to see more chromatic aberration, but did not notice any. I'll process the images tonight to see how good they really are. The moon just barely fit in the field of view. I also imaged Jupiter and Neptune. The belts on Jupiter were nicely recorded.

So my next question is, will the new Canon 2x TC III stack with the older 2x II? I'll buy a second 2x TC and would hope the new TC will give better performance than the 2x TC II (which is already very good and a notch above the Kenko pro 300).

Roger

[Arthur Morris]

Thanks Roger. I figured that you were trying to focus on the edge of the moon and your explanation makes more sense than mine. I figured that that would happen as the technical knowledge in one of your fingernail clippings far exceeds the technical knowledge in my entire brain.

[Roger Clark]

Thanks Roger. I figured that you were trying to focus on the edge of the moon and your explanation makes more sense than mine. I figured that that would happen as the technical knowledge in one of your fingernail clippings far exceeds the technical knowledge in my entire brain.

Artie
But my fingernail does not have your experience in photography, and neither does the rest of me.;)
Roger

[Arthur Morris]

Thanks for your kind words. I do hope that we get to meet someday.

[Roger Clark]

Thanks for your kind words. I do hope that we get to meet someday.

Actually, We have met a couple of times, casually, long before BPN. Once at Bosque, and one morning at the Venice Rookery.

Roger

[adrian dancy]

Roger

As I once stated to you before I am a TI (technical idiot!) but I wonder if you might have a problem focusing because of the degree of shake or mico movements that occur owing to the powerful focal lengths you are employing and could it be that the mechanism of fucus in the lens is not so highly tuned that it can accommodate such a fine degree of tuning/focusing.

I also wonder what support you are using. I most certainly would not use a tripod alone. I think if I were to do such 'extreme' photography' I would be using something that would support the whole lens and camera. Also with such huge focal lengths I would not put the rig on something that would transfer vibrations easily from the ground though I dare say that you have that issue covered?. Just my tuppence worth.

Regards

Adrian

p.s. I would love to be a fly on the wall if your goodself and Art met....I would either learn a huge amount or nothing ...probably the latter but I'm sure it would be fun :D

[Arthur Morris]

Actually, We have met a couple of times, casually, long before BPN. Once at Bosque, and one morning at the Venice Rookery. Roger

Wish that I had known then how smart you were....

[Roger Clark]

As I once stated to you before I am a TI (technical idiot!) but I wonder if you might have a problem focusing because of the degree of shake or mico movements that occur owing to the powerful focal lengths you are employing and could it be that the mechanism of fucus in the lens is not so highly tuned that it can accommodate such a fine degree of tuning/focusing.

Adrian,
This is a good question. I believe it is not much of an issue for several reasons. I have no issues with stacked 1.4 + 2x TCs. I'm using a good carbon fiver tripod (see blow), and I'm using a cable release to activate the AF with a half press of the shutter.



I also wonder what support you are using. I most certainly would not use a tripod alone. I think if I were to do such 'extreme' photography' I would be using something that would support the whole lens and camera. Also with such huge focal lengths I would not put the rig on something that would transfer vibrations easily from the ground though I dare say that you have that issue covered?. Just my tuppence worth.


I'm using a gitzo 1325 carbon fiber tripod with full wimberly (type 1). I did the exposure of the Moon from my driveway with the tripod on concrete. I tested the lens+TCs+camera laying on a granite counter top and got similar results.

I also have large telescopes and tracking mounts (e.g. 100 pound Losmandy G11 telescope equatorial mount) and several telescopes, one a 2000 mm f/6.3 (that is a 12.5-inch aperture) Newtonian which could get better images. But I want to see what I can do with photographic lenses. Each time I push them to new limits, I am impressed!

Roger

[Charles Glatzer]

Chas,
I'm do not see why you can not stack 2 canon 2x TCs without a spacer. The protrusion out the front and the hole in the rear seem the same as the 1.4x and one can stack the 2x and 1.4x TCs.

Roger

Roger,

You are correct, it is two 1.4x that cannot be put together. Jet lag has gotten the better of me ;)

Best from Jasper

Chas

[Roger Clark]

An update.

I successfully imaged the Moon, Jupiter and Neptune with 500 mm f/4 + canon 2x TC + kenko pro 300 2x TC + 1d Mark IV with autofocus. The Moon was at 1/100 second f/16 and are quite sharp. For jupiter I had to drop to 1/50 second and even with mirror lockup, there is some shutter bounce that was not obvious on the Moon at 1/100 second. The amount of bounce is about 1/2 a diffraction disk diameter (about 2 arc-seconds). This robs some fine detail, but the attached image shows what I got on Jupiter. I averaged 3 frames to reduce noise, and did a custom richardson-lucy deconvolution using a blur pattern derived from one of Jupiter's moons. Then a little contrast stretch in photoshop using curves. Several belts can be seen and hints of detail in the dark belt. I'll add a brace and see if I can reduce the shutter bounce, and then I think there will be a lot more detail.

Roger

[Joerg Rockenberger]

Roger, have you considered tethering your camera to a laptop and controlling then the focus from the EOS utility software? Not sure if that works for a 1D camera but it is possible with the 40D. That would eliminate the need to touch the lens when AF fails and might allow you to use even more stacked TCs.

Great images by the way. Someone better give/loan you a 800mm... :)

Best, Joerg

[Roger Clark]

Joerg,

That is an interesting idea. I was not aware that you could control the focus with a laptop. Can you nudge the focus a little bit to improve focus without touching the lens? I assume this is using live view. Can you control how much a "nudge" is?

Roger

[Joerg Rockenberger]

Joerg,

That is an interesting idea. I was not aware that you could control the focus with a laptop. Can you nudge the focus a little bit to improve focus without touching the lens? I assume this is using live view. Can you control how much a "nudge" is?

Roger

Yes, it relies on Liveview. You'll see the live image on your monitor along with a live histogram in a separate window. And there are fine/medium/coarse focus adjustment buttons. But while the "nudge" of those can't be changed the "fine" focus adjustment buttons have pretty small steps. Not sure though if it is sufficient for your purposes. You can magnify the live image ("actual" and 200%) to improve the focus adjustment. Then you take the shot by clicking on a button in the EOS utility program. You also can control all exposure settings from there. All without touching the camera or lens.

Let me know if you need more info. Best, JR

[Arthur Morris]

Wow, Joerg. That is amazing stuff. One of the things I love most about BPN is that different folks know so much different stuff....

[Joerg Rockenberger]

Thanks. Glad to be able to give something back to the community. Best, JR