tjkraemer1 Loc: Maryland

I appreciate the quick reply John. The issue is weather to set the target at the crop magnification distance or not. (100-400mm vs 160-640 canon 1.6 crop) Would you set the target at 32' (400 equivalent) or 65' (640 equivalent) for the long end.

CanonTom Loc: Birmingham

Following with great interest.

John Gerlach Loc: Island Park, Idaho

I am only looking at mirrorless to see if they can do something my DSLRs can't and because many of my workshop clients have gone to mirrorless and I know I need to be familiar with them, but I am in no hurry to get mirrorless as I know they will rapidly improve.

JCam Loc: MD Eastern Shore

John, Is that A1 Microadjust calibration tool part of the Canon Tools menu in the camera? I'm using an older (2013) Canon 60D with the Canon kit 18-135mm lens or a Tamron 70-300mm lens and have been mostly happy with their performance. The Tamron was recently sent to the Canon Repair Facility in NY for repair and adjustment to the camera after a catastrophic collision with our stone patio floor, but I haven't used the camera much with either lens since the repair as it has been either too cold or wet.

Thanks for any info you may be able to give me.

Jim

TriX Loc: Raleigh, NC

The 60D does not have user microfocus adjustment capability.

saxman71 Loc: Wenatchee

This is the type thread I always hope to find when I open up the UHH site each morning and scan the main photography section. Useful information that may in fact answer nagging questions I have or suggestions that may help me to take better photos. Thank you John. I purchased a Nikon 80x400 MM lens (newer version) a few years back. I have never been happy with the "soft" images I get and it pains me to say it took me so long to determine it was the lens and not me causing the problems that returning the lens was no longer an option. I did fool around a bit with micro adjustment but never did any testing as extensive as you lay out. I plan to give your method a try as soon as the weather clears and I get a $100 bill in my hands. BTW - your web site is superb.

Benzzeze Loc: Tucson, Arizona

What camera bodies are your using? I shoot with a 1Dx, 5Ds, and have a 7D Mk II as a backup. I also have the 16-35 mm f2.8, 24-70mm f2.8 Mk II, 70-200mm f2.8 Mk II, 100-400mm f4.0-5.6 Mk II, 400mm f2.8, and the 600mm f4.0. I shoot Wildlife, Landscapes, Sports (professional soccer), and never had too micro - adjust for any of my lenses. The variations in your micro adjustments seems to be extreme. I have never needed to micro adjust for any of my lenses. I know your discussion is more about weather auto focus is more accurate than manual and TTL focusing versus mirrorless focusing, but but your need to micro adjust seems odd. Have you ever had your lenses recalibrated?

Fotoartist Loc: Detroit, Michigan

I notice no Nikon owners have this issue.

TriX Loc: Raleigh, NC

Just two points. Have you actually checked the AF calibration of each of your lenses, and if not, how do you know if they need calibration or not? And if the answer is that your shots are sharp, how do you know whether or not they could be sharper if properly calibrated? Secondly, if you typically shoot outdoors and/or in good light, then since you’re shooting with a decent DOF, you may not notice an AF that is off - the error is hidden by the DOF. On the other hand, if you shoot wide open and especially with lenses of f2 or faster, you may find that having the AF off even an inch or two when the DOF is 6” is enough to be noticeable.

wdross Loc: Castle Rock, Colorado

How can he? It really is that good a camera. It will be interesting to see if he gets the G9 or the GH5 or GH5s. My guess is he drools a little as he walks past the Panasonic counter in the camera store.

Benzzeze Loc: Tucson, Arizona

I had an issue with my 600mm and did my own testing on the micro adjustment calibration features and the adjustments did not help. I sent the the lens back into Canon and they recalibrated the lens, and since then, I have had no focusing or image problems whatsoever. I also check my lenses for sharpness, particularly when I'm using the 600 and 400 by zooming in to 100 to 200%. I understand the effects of depth of field, but the fact that he is having to adjust to such extremes makes me think there is something wrong with the equipment.

Bipod

I am not an autofocus expert. It would be interesting to hear from someone who is.
However, I do know this: all technologies--including manual focus and AF -- have limitations.

All current cameras use passive autofocus -- which can never match the extreme precision of say, laser transits
(which require a reflective target -- a roof prism) or even of X band (and shorter wavelength) radar.

Passive AF isn't just one technology: at least two radically different types are in current use: phase detection and
contrast detection. Many cameras use both. AF is controlled by firmware, and various algorithms are in use.

So the important thing is to know how the AF in your camera works, and to know it's particular limitations.
(On this you will get very little help from your camera manufacturer, who instead will brag about "19-point
autofocus" or whatever.)

In general, AF is likely to have trouble:
* In low-light situations
* With narrower apertures
* In cameras with smaller sensor formats:
* With subjects having little texture (low local constrast)

In some situations, autofocus will fail, and you will need to manual focus.
But first, you'll have to be able to tell that the image is not in focus!

Unfortunately, most DSLRs (and all EVF cameras) have removed optical
focusing aids. That leaves you with only live-view magnification --
hunting around in the seen for some texture to magnify.

All autofocus systems can fail. So you have to have some way to check
the focus. Live-view magnfication is rather cumbersome.

Both phase-detection and contrast-detection work by triangulation.
Therefore, accuracy is limited by the distance between the two sensors.
On current cameras, both beams used by the rangefinder come through
the lens. So they can be no further apart than the diameter of the
aperture,

At f/22, AF is a roll of the dice. Fortunately, depth-of-field is large,
so you probably won't notice the error. But if you were counting
on using all of that depth-of-field, you lose: either the near or far
part of your image will be more blurry than it ought to be.

Compare this to a rangefinder camera (e.g. a Leica), where the ranefinder
window could be three or four inches from the viewfinder!

Most DLSRs have a semi-transmissive window in the mirror which allows
part of the image to fall on the autofocus sensor. But in mirrorless designs,
the autofocus sensor is located on the image sensor itself, usually on two
opposite edges. But both are limited by aperature diameter.

What you will find satisfactory depends on what you are photographing, and
for what purpose. For example, cinematographers use a tape measure, not AF,
for all scenes involving actors. Why? Because shoot quite frequently with
shallow depth-of-field, and focus mistakes are very costly in film-making.

Even with a digital still cameras, focus mistakes are likely not go get noticed
in the field. Only when you view the image on a monitor (or worse still,
print it) will you say "Dang, it's not in focus!"

Tape measures (and yardsticks) are also common in close-up photography,
because of the extremely shallow depth-of-field.

The trick with AF is knowing when not to use it, because you probably won't
notice when it fails until it is too late to do anything about it.

“The single most important component of a camera is the twelve inches behind it.”
– Ansel Adams

John Gerlach Loc: Island Park, Idaho

I get it now. I haven't been to keen to follow the suggestions that closely. I tend to use about 20 yards for my bigger lenses so the focus target was large enough that I could see it when I magnified the image of the target with software to 100%, and while I knew the Canon distance guidelines, I thought it was silly to go by them when I was trying to get my 100-400mm to focus accurate on chickadees and hummingbirds at the closest focus distance, so I ran the test at the distance I would be making my images for them and that worked perfectly. It would be interesting to see if the AF microadjustment is different at the closest focus distance and infinity focus for a lens. Haven't tried that.

John Gerlach Loc: Island Park, Idaho

Thanks for the input. It helps to clarify some things for me and also encourages me to go the way I have and that is manual focus using live view whenever possible, or using the AF by touching the LCD. When that isn't possible, then I rely on AF microadjustment, using a few different focus patterns that depend on the subject, and adjusting the 3 Canon focus parameters for various situations.

John Gerlach Loc: Island Park, Idaho

I am fortunate to not have focusing problems so severe that microadjusting doesn't solve the problem. All of the lenses I have tested - about twenty of them - have required no more than a -9 correction to -3, and my adjustment scale goes to -20 to +20. But, if I did find a lens that nothing in this range will work, then I would have to send it in.