An AF at f/8 Primer « Arthur Morris/BIRDS AS ART

An AF at f/8 Primer

What’s Up?

I am somewhere in South America. I hope that you are well. Jim and Jen are at the office most days to help you with your mail order needs and Instructional Photo-Tour sign-ups. I still need folks for San Diego, Japan, Galapagos, the Palouse, and the Bear Boat (Grizzly Cubs) trips. Among others 🙂 Please e-mail for couples and discount info for all of the above. Click here for complete IPT info.

I will have intermittent internet access for the rest of my South American adventure. I get back home late on December 25, 2016. Best and great picture making, artie

Gear Questions and Advice

Too many folks attending IPTs and dozens of the folks whom I see in the field, and on BPN, are–out of ignorance–using the wrong gear, especially when it comes to tripods and more especially, tripod heads… Please know that I am always glad to answer your gear questions via e-mail.

The Streak: 372!

Today’s blog post marks a totally insane, irrational, illogical, preposterous, absurd, completely ridiculous, unfathomable, silly, incomprehensible, what’s wrong with this guy?, makes-no-sense, 372 days in a row with a new educational blog post. There should be no end in sight until my big South America trip next fall. Or not… As always-–and folks have been doing a really great job recently–-please remember to use our B&H links for your major gear purchases. For best results use one of our many product-specific links; after clicking on one of those you can continue shopping with all subsequent purchases invisibly tracked to BAA. Your doing so is always greatly appreciated. Please remember: web orders only. And please remember also that if you are shopping for items that we carry in the new BAA Online Store (as noted in red at the close of this post below) we would appreciate your business.

An AF at f/8 Primer

Though this is a topic that I have been over before here many times, it is obvious that some folks are still confused. Below I am trying a slightly different educational tack. If you are still confused, please leave a comment and specify whatever is bugging you.

Below is an e-mail exchange with Larry Gawne

am: Hi Larry, re:

LG: Enjoy greatly starting my day with a coffee and reading your posts. I have learned a great deal from the efforts you put into your post.

am: 🙂 and thanks.

LG: Artie, I have read several time AF @F8 and do not understand what is meant by this.

am: It means that when you are forced to work at f/8, as with an f/4 lens and a 2X TC, or an f/5.6 lens and a 1.4X TC, that AF will function (at least to some degree) with the wide open aperture of f/8. No camera presently in production can focus when you are forced to work at f/11 (a with an f/5.6 lens and a 2X TC).

LG: When in Florida photographing at Circle B Bar Reserve my best combination is a 7D Mark II with a 70-200 2.8 and 2X teleconverter.

am: That has you working at f/5.6 so you have AF all the time with all AF points with any camera body.

LG: My other long lens is a 50-500 which I find to slow of focus for flight. I am considering the 50-500 and going with the 100-400 II.

am: I would strongly recommend selling the 50-500—which one is it?, and getting the Canon 100-400 II and the 1.4X III TC.

LG: … and then possibly a 1.4X or using my 2X which would put me at F11.

am: As above, you would need to manually focus at f/11, in other words, no AF.

LG: Thus the concern when I hear about the AF @f8.

am: Ah, it seems as if you may have understood it after all 🙂 Do know that when you are forced to work at f/8 some cameras give you just the middle AF point (plus four assist points if you wish) while the latest bodies, the 1DX II and the 5D Mark IV, let you pick any AF point and any AF Area Selection Mode.

LG: Sorry for my ignorance on this but just don’t know the whole story.

am: I am glad that you asked.

LG: Also can you please tell me the process to for you to receive credit when I purchase the lens from B&H.

am: Many thanks. Please remember web orders only. You can always click on the B&H logo-link on the top right side of each blog post. Or, you can use any of the many product specific links on the blog, or in this specific case, you can use these:

Canon EF 100-400mm f/4.5-5.6L IS II USM lens

Canon Extender EF 1.4X III

later and love, artie

ps: let me know if you have any additional questions.

Please Remember to use my Affiliate Links and to Visit the New BAA Online Store 🙂

To show your appreciation for my continuing efforts here, we ask, as always, that you get in the habit of using my B&H affiliate links on the right side of the blog for all of your photo and electronics purchases. Please check the availability of all photographic accessories in the New BIRDS AS ART Online Store, especially the Mongoose M3.6 tripod head, Wimberley lens plates, Delkin flash cards and accessories, and LensCoat stuff.

As always, we sell only what I have used, have tested, and can depend on. We will not sell you junk. We know what you need to make creating great images easy and fun. And we are always glad to answer your gear questions via e-mail.

I would of course appreciate your using our B&H affiliate links for all of your major gear, video, and electronic purchases. For the photographic stuff mentioned in the paragraph above we, and for everything else in the new store, we, meaning BAA, would of course greatly appreciate your business. Here is a huge thank you to the many who have been using our links on a regular basis and those who will be visiting the New BIRDS AS ART Online Store as well.


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3 comments to An AF at f/8 Primer

  • avatar Arthur Morris/BIRDS AS ART

    Thanks Mike H.

    Arnie, my understanding is that if you photograph from the same bird from the same spot with a full frame and a crop body with the same focal length that the d-o-f will be the same …

    a in Lima, Peru

  • avatar ARNIE LLOYD

    Art, does having a cropped sensor also effects the f-stop value?

    • avatar MikeH

      It does not affect the working AF for the lens – an f5.6 lens is f5.6 on APS-C and on FF so will not affect the focussing as described above.

      When it comes to the final image, there are so many variables:
      If you frame a APS-C shot the same as a FF shot from the same position, it means you will have used a wider angle lens on APS-C. So both lenses set at f5.6 the APS-C will have greater DOF.
      If you use the same lens then you have to move further away with the APS-C shot to get the same framing. The greater distance gives greater DOF with APS-C.

      With birds, where you are limited by how close you can get the chances are you will crop both images (APS-C and FF) to the same FOV. Sensor size then becomes irrelevant and the DOF is then dependent on pixel density.