Rear Focus Tutorial « Arthur Morris/BIRDS AS ART

Rear Focus Tutorial

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This Marbled Godwit was photographed at Nickerson Beach at 6:51 am on August 30, two days after Hurricane Irene. (If you missed “Surreal Hurricane Irene Experience” be sure to click here.) Marbled Godwit is uncommon at best at this location. The image was created with the tripod-mounted Canon 800mm f/5.6L IS lens, the 1.4X III TC, and the EOS-1D Mark IV. ISO 400. Evaluative metering +1 stop: 1/500 sec. at f/9 in Manual mode. Central Sensor/Rear Focus AI Servo AF and re-compose. Read on to learn about rear focus.

Lens/TC/Camera Body Micro-Adjustment: 0.


Blog-folks who read the captions carefully have noticed recently that I have been adding rear focus info to most images. In the Marbled Godwit image caption above I wrote, “Central Sensor/Rear Focus AI Servo AF and re-compose.” With the 800mm lens, the 1.4X III TC, and a pro body (the Mark IV), only the central sensor is active. Unless you know what you are doing having only the central AF sensor available can lead to problems. As I have written before, many folks become compositional slaves to the central sensor especially when working in AI Servo AF (as opposed to using One-Shot AF and re-compose). Nikon folks, not to worry. Nikon does offer rear focus. Please consult your camera body manual. Or better yet, get yourself a copy of our Nikon dSLR User’s Guide here. Note: Canon’s “AI Servo AF” is the same as Nikon’s “Continous” (C) and likewise, Canon’s “One Shot” is Nikon’s “Single Servo” (S).

Rear focus involves focusing by pushing a button on the top right back of the camera (rather than by pushing the shutter button). You need to change a custom function or two to set up rear focus. And with some systems you set up rear focus via the camera’s menu. You can consult your camera body to learn to set up rear focus. Canon folks are urged to consult our camera User’s Guides for detailed information on exactly how I set up my cameras for rear focus. Set-up is similar with the Mark III and the Mark IV and with these bodies I recommend swapping the functions of the Star and the AF-On buttons. Set-up with the 7D is totally different. In each case the User’s Guide contains detailed instructions for setting up rear button AF. (Many folks are simply unable to decipher their camera body manuals.)

For many years I used both the shutter button and rear focus, depending on the situation. Often I got confused. I’d forget which was set on which camera. I’d press the shutter button and the camera did not focus. Or I’d press the rear button and the camera did not focus. About five years ago I gave up and went shutter button AF all the way spending half my time switching from AI Servo to One-Shot and back again…. Robert O’Toole has always used rear button focus and about a year ago he convinced me to make the switch full time. He believes that when the shutter is released that AF tracking may be momentarily interrupted but that when you use rear focus the camera continues to track well even when the shutter is released. Canon’s top tech reps are noncommittal but concede that it could be possible.

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This young skimmer was photographed at Nickerson Beach at 8:26 am on August 19 at Nickerson Beach with the tripod-mounted Canon 800mm f/5.6L IS lens and the EOS-1D Mark IV. ISO 400. Evaluative metering +2/3 stop: 1/1600 sec. at f/6.3 in Manual mode. Two sensors below the central sensor/Rear Focus AI Servo tracking AF. See more below.

Lens/Camera Body Micro-Adjustment: -4.

Making the change from the shutter button to rear focus requires a big commitment and takes lots of getting used to; it takes a bit of retraining of the brain and the thumb to get used to rear focusing.. But I have stuck with it for more than a year now and will never go back.

Aside from possibly better AI Servo AF tracking for flight photography there are other advantages to using rear focus. In short, you have the best of all worlds all the time. When using rear focus you always have AI Servo (Continuous for Nikon) set. You will never need to switch back and forth from AI Servo to One Shot. To photograph flying birds or to focus track walking, running, or swimming birds (or perched birds that are changing their posture or head position almost continuously simply press and hold the rear button to focus track that you have set for AF and press the shutter button when you want to create an image.

If you are limited to the central sensor when photographing a static bird like the Marbled Godwit above, you first place the active sensor on the subject’s eye, face or neck. Then you press the rear button too set the focus and then you release it. This effectively “locks” the focus–the system will not begin to focus until you press the rear button again. Now you can recompose without worrying that the system will focus. Finally you press the shutter button to make an image. If the bird moves or takes off you simply press and hold the rear button to activate AI Servo tracking AF. With rear focus you have the best of both worlds available at all times: you always have what effectively amounts to One Shot AF (by pressing and releasing the star button or the AF-ON button, whichever one you use for rear focus) and you always have AI Servo Tracking AF by pressing and holding the star button or the AF-ON button, whichever one you use for rear focus.

Once I made the commitment to switch exclusively to rear button AF I stuck with it and have never looked back. I have it set 100% of the time with both my 800 and my 70-200. And I do feel that my percentage of sharp flight images with either lens has increased.

Hugely important note: when hand-holding and in many other situations where you are photographing a static bird and have access to all the AF sensors, it often makes sense to select a sensor that falls on the bird’s eye, face, head, or neck and push and hold the rear button. With the Marbled Godwit image above I had only the central sensor available so I needed to rear focus and re-compose.

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This BreezeBrowser screen capture shows what I mean by “two sensors below the central sensor” (in red). To create this image I pushed the rear button (I actually use the Star button) to acquire focus and held it in to track the bird. When the bird came into the zone I pressed the shutter button and held it down to create three or four images. This one was best by far.

Note the micro-adjustment and the perfect histogram. BreezeBrowser is the program that I use to edit (select the keepers) my images and to organize my image files both on my laptop and on the big computer in the office. If you are using a PC and you are not using BreezeBrowser you are wasting lots of time….

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Here, a juvenile Willet is holding its sand crab breakfast while an adult Sanderling is hoping that the young bird drops its prey item. This image was created at 6:21 am on August 31, 2011 at Nicerkson Beach with the tripod-mounted Canon 800mm f/5.6L IS lens and the EOS-1D Mark IV. ISO 400. Evaluative metering +2/3 stop: 1/1600 sec. at f/6.3 in Manual mode. Single sensor lower right/Rear Focus AI Servo tracking AF. I was able to get the manually selected sensor on the Willet’s right (far) foot. I do wish that that Sanderling had been more parallel to the back of the camera.

Lens/Camera Body Micro-Adjustment: -4.

The pretty pink reflections here were opposite the rising sun. On clear mornings always look to the west/southwest for the pink/purple/blue skies.

This image was created on the morning of Sunday, September 4, 2011 with the Canon 70-200mm f/2.8L IS II lens and the 1.4X III TC (hand held at 205mm) with the Canon EOS-1D Mark IV . ISO 100. Evaluative metering + 2 2/3 stops: 1/8 sec. at f/6.3 in Manual mode. Bottom row central sensor/rear-focus AI Servo AF.

Lens/camera body Micro-adjustment: -8.

For a greater appreciation of the image above, click on the photo to view a 1400 pixel wide version. Click on the enlarged version to close it.

Many beginning photographers think that pleasingly blurred images are created by accident. Nothing could be farther from the truth. If you would like to learn to create a variety of pleasing blurs, check out A Guide to Pleasing Blurs by Denise Ippolito and Arthur Morris.

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This image of a Semipalmated Sandpiper flapping after its bath was made at Nickerson Beach at 6:03pm on August 30, two days after Hurricane Irene. My big lens was on my Mongoose M3.6 head as usual. I lay behind my splayed, tripod-mounted Canon 800mm f/5.6L IS lens with the 1.4X III TC and the EOS-1D Mark IV. ISO 400. Evaluative metering +1/3 stop (as framed): 1/800 sec. at f/10 in Manual mode. Central Sensor/Rear Focus AI Servo AF; release and wait for the jump!

Lens/TC/Camera Body Micro-Adjustment: 0.

Most time when trying to catch a shorebird jumping after its bath I would keep the rear button down and try to follow the bird. On this afternoon I tried something new. I focused on the bird with the rear button as it splashed about. Then I would release the rear button and re-frame higher as the birds almost always just flies straight up out of the water. When the bird jumped, I held the shutter button down for an image or two. Here this new trick worked to perfection. To be sure that you understand completely: I was not actively focusing when this image was created….

BAA Bulletin 384

BAA Bulletin 384 is online and can be accessed here.


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This sleeping juvenile Sanderling image was created with the the tripod-mounted Canon 800mm f/5.6L IS lens, the 1.4X III TC, and the EOS-1D Mark IV. ISO 800. Evaluative metering at zero: 1/1000 sec. at f/8 in Manual mode. Central Sensor/Rear Focus AI Servo AF and re-compose.

Lens/TC/Camera Body Micro-Adjustment: 0.

This image perfectly illustrates one of the huge advantages of using rear focus. With the TC and an f/5.6 lens I was limited to the central AF sensor. I focused on the eye of the bird by pressing the rear button, let it go to effectively “lock” focus, re-composed, and then created the image with the bird right where I wanted it.

Shopper’s Guide

Below is a list of the gear used to create the images in today’s blog post. Thanks a stack to all who have used the Shopper’s Guide links to purchase their gear as a thank you for all the free information that we bring you on the Blog and in the Bulletins. Before you purchase anything be sure to check out the advice in our Shopper’s Guide.

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Canon 70-200mm f/2.8L IS II lens. Man, I am loving this lens on my shoulder with the 2X III teleconverter. I also use it a lot with the 1.4X III TC.
Canon 800mm f/5.L IS lens. Right now this is my all time favorite super-telephoto lens.
Canon 1.4X III Teleconverter. Designed to work best with the new Series II super-telephoto lenses.
Canon EOS-1D Mark IV professional digital camera body. My two Mark IVs are my workhorse digital camera bodies.

And from the BAA On-line Store:

LensCoats. I have a LensCoat on each of my big lenses to protect them from nicks and thus increase their re-sales value. All my big lens LensCoat stuff is in Hardwood Snow pattern.
LegCoat Tripod Leg Covers. I have four tripods active and each has a Hardwood Snow LegCoat on it to help prevent further damage to my tender shoulders 🙂
Gitzo GT3530LS Tripod. This one will last you a lifetime.
Mongoose M3.6 Tripod Head. Right now this is the best tripod head around for use with lenses that weigh less than 9 pounds. For heavier lenses, check out the Wimberley V2 head.
CR-80 Replacement Foot for Canon 800. When using the 800 on a Mongoose as I do, replacing the lens foot with this accessory lets the lens sit like a dog whether pointed up or down and prevents wind-blown spinning of your lens on breezy days by centering the lens directly over the tripod.
Double Bubble Level. You will find one in my camera’s hot shoe whenever I am not using flash.
Be sure to check out our camera body User’s Guides here.
The Lens Align Mark II. I use the Lens Align Mark II pretty much religiously to micro-adjust all of my gear an average of once a month and always before a major trip. Enjoy our free comprehensive tutorial here.
Canon EOS-1D Mark IV User’s Guide. Learn to use your Mark IV the way that I use mine.

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