Bosque Blastoff at 700mm

[Kerry Perkins]

Thanks to the generosity of Doug Brown I was able to shoot with his 500mm f/4 lens for a few days last autumn at Bosque del Apache. The snow geese are everywhere at that time of year and the blastoffs can be spectacular. I was intrigued by the compression (objects at different distances appear to be closer to each other than they really are) that comes with magnification. Putting my 1.4x TC on this lens plus the 1.6x crop factor of the 7D made for quite an interesting capture tool. This was captured in the early morning, before 7am so the light was nice. I will be in New Mexico the week before Thanksgiving and hope to see some of you there!

7D, EF500mm f/4L + 1.4x TC
Manual mode, f/7.1@1/2500 ISO 400 WB 5100K
AI Servo autofocus, hand-held no flash

[Ian Cassell]

Kerry, I love those blast-offs! I might be tempted to crop just a bit above that brown in the bottom left. See ya' in November!

[Jeannean Ryman]

Very cool shot! That's a LOT of birds!!!

[Nancy Phillips]

This is a lovely photo of an impressive experience. There's a popular migration stop-off ox-bow lake in Calhoun Co, IL, near St. Louis MO, and I have been privileged to see the take-off and circle-around flight of 2,000 or more snow geese. What is nice about this photo is that almost all of the bird profiles are in focus, in other words, you had a near-vertical wall of birds flying by without many birds in front of the focal plane. I like the little brown bit at bottom left, it is more or less in line with the upper right brown patch and parallel with the birds. I think that the negative space brown and yellow is essential for the composition to work.

I also liked your photoshop creative version in the creative post processing forum.

[Nancy Phillips]

A question: How do you get your 7D to autofocus at f/7.1? Or did you mean f/5.6 (wide open). A 400mm f/5.6 L, TC 1.4 II, 60D owner wants to know - I have contemplated trying the tape-the-contact method some people use to outwit the AF of non-1 series Canons that refuse AF beyond f/5.6. I rather hate to potentially gum up any contacts.

[Kerry Perkins]

Nancy, the lens I was using for this shot is a 500mm f/4, not the 400mm. Autofocus is calculated by the camera body with the lens wide open, which is f/5.6 in this case (1.4x TC subtracts one stop from the lens, which equals f/5.6 on an f/4 lens). You can shoot at f/32 if you want, it doesn't matter. All that matters is the maximum aperture allowed by the lens/tc combination. The reason the 400mm f/5.6/1.4x won't autofocus with the 7D is that the 7D autofocus drops out at f/8, which is one stop less light than f/5.6. Make sense? When you say "non-1 series Canons that refuse AF beyond f/5.6", I assume that you mean "f/5.6 plus 1.4x TC", which equals f/8 and the only bodies that will autofocus in that case are the 1 series. Even at that, you only get the central focus point. I shoot both the 7D and the 1D4, and even though autofocus works with the 1.4x on the 400mm f/5.6 it is not that good. It works ok for static subjects in bright light but not very well for BIF and forget about it in low light conditions.

[Ian Cassell]

Interesting, Kerry. My 7D will not AF with my Sigma 1.4x even in bright light on static subjects.

[Kerry Perkins]

Ian, I'm pretty sure that TC is not reporting to the body properly. I'm not surprised that it doesn't autofocus. This TC is designed to be used with Sigma lenses and it doesn't even autofocus with a majority of them.