EF 70-200 f/4L Autofocus on Tamron 2x Tele-Converter (Long Post)

[GTogs]

I recently purchased the EF 70-200 f/4L lens. When I was checking this lens out indoors the night I received it due to inclement weather, I tried it out with both of my Tamron teleconverters, (Models 1.4X C-AF1 MC4 and 2X C-AF 1 BBAR MC7) imagine my surprise when this lens autofocused with the 2X converter!

I chalked it up to a fluke!

Yesterday, I tried using both of the teleconverters with this lens, same thing.

So today, I set up my tripod and took shots of an old pump we have in our yard. I took pictures with out the telecons at 70mm, 131mm and 200mm. I then took pictures with each of the teleconverters at the same focal lengths. The following links lead to crops of those photos. All pictures were taken in AV Mode @ f/8. They are posted without any PP other than the crop.

http://members.aol.com/foggie65/70x200-70mmCrop.jpg

http://members.aol.com/foggie65/70x200-131mmCrop.jpg

http://members.aol.com/foggie65/70x200-200mmCrop.jpg

http://members.aol.com/foggie65/70x200-1.4x-70mmCrop.jpg

http://members.aol.com/foggie65/70x200-1.4x-131mmCrop.jpg

http://members.aol.com/foggie65/70x200-1.4x-200mmCrop.jpg

http://members.aol.com/foggie65/70x200-2.0x-70mmCrop.jpg

http://members.aol.com/foggie65/70x200-2.0x-131mmCrop.jpg

http://members.aol.com/foggie65/70x200-2.0x-200mmCrop.jpg

I did a modicum of sharpening on the last photo using the high pass method and this is the results:

http://members.aol.com/foggie65/70x200-2.0x-200mmCropSha.jpg

Has anyone else experienced this?

I found this on a discription of these teleconverters on the Canoga Camera site:

"The 1.4X teleconverter can be used with both AF and MF lenses. AF will be retained if the master lens is F/4.5 or faster. AF will be retained with the 2X teleconverter if the master lens is F/4.0 or faster."

[cfcRebel]

Interesting. How much are the Tamron TCs?

[Mac]

Yeah mine also with AF with my TC on it. I just manual focus anyway...I am afraid it will damage the AF motor or something...maybe I am just paranoid...hehe :D

[Cadwell]

Those Tamron converters don't report the revised max aperture back to the camera. That's why AF still works (sort of). If there's enough light then the camera can AF but with a 2x on an f/4 lens anything but a 1 Series body is working outside of normal specification. AF accuracy/speed might not be as good as you would normally expect.

[ron chappel]

Yes,AF doesn't suddenly quit above f5.6. It just gets less reliable.
Some lenses like the sigma 100-300/4.5-6.7 DL or those sigma 135-400mm things simply lie to the camera about the max aperture at the long end.They work fine :)

[mr.photoguy]

pretty good results @ 1.4x, and also at 2x.
I am suprised at the quality of the lens with the 2x.

[robertwgross]

Since the teleconverter is lying to the camera about apertures, you might get some interesting exposure solutions. You might get one stop or two stops underexposed.

Try this:
Set up a shot with a normal exposure with just the lens and no teleconverters. Get it so that the histogram shows light almost right up against the right side. Snap that.

Now put on one teleconverter and set up the shot exposed the same way. Snap that. Now compare the first histogram with the second one. On the second one, you may see the one stop or two stop underexposure, and you may see the histogram breaks off one stop or two stops down from the right side.

---Bob Gross---

[GTogs]

Bob, I will try that test tonight and post the results.

cfc, I paid $79 for the 1.4x online and $179 for the 2X locally. Seems like they are mostly out of stock today.

Just an interesting sidelight, I actually got a Tamron 28-300 f/3.5 - 6.3 to autofocus with the 1.4X @ 300mm. Picture quality was OK.

[Cadwell]

B
cfc, I paid $79 for the 1.4x online and $179 for the 2X locally. Seems like they are mostly out of stock today.

I believe they are out of production.

[GTogs]

I did the test that Bob suggested. I shot one with the histogram just at the right side. I then shot one with the 1.4x Telecon, the histogram just about centered. The shot with the 2x shifted the histogram hard to the left side.

[gcogger]

Was that letting the camera do the metering, or in manual mode?

[GTogs]

It was in manual mode, f/8 and shutter speed of 80.

[willg]

thats a lot of zoom with the 2x teleconverter + the crop factor...may i ask what you are shooting? i have recently become very interested in the 70-200 f/4

[GTogs]

This was just a test of the ability of the 70-200 f/4L to autofocus with the Tamron 2x C-AF 1 BBAR MC7 Teleconverter. I shot the pics linked above of an old pump we have in our yard.

Togs

[rowdyred94]

Thought I'd add some value to this thread. I have a borrowed Tamron 2x TC, and recently got a 70-200 f/4L. I was fairly happy with the focusing on a walk with my little boy today, though it did hunt a bit in scenes with little geometry, so to speak. While IQ certainly drops from the L alone, I found it quite usable. I chose to shoot at ISO 800 to eliminate shake. I was using a monopod. I think I could have gotten away with ISO 400, though. It was heavy overcast today.

These were shot at f/4 (indicated) and 200mm (400mm total). I applied sharpening of 50/1.0 in Lightroom.

[Calzinger]

I'd love to see some more 100% crops of the 70-200 and 2x as I'm looking into this combination. Of course I've been told over and over that the 2x degrades IQ like crazy, but $130 for a 2x is a little different than $1400 for the 100-400.

[rowdyred94]

I intend to take this combo on a wildlife outing soon, so I'll be sure to stop back with more samples.

[jfarsang]

I intend to take this combo on a wildlife outing soon, so I'll be sure to stop back with more samples.

Thread revival.

Anymore samples ? :)