May 16th, 2011

Micro Adjustments II

After a lot of talk, discussions, new insights and a new Lens Align device, I will spend a new blog post on the topic of MicroAdjustments, further abbreviated as MA in this article. My previous post on this topic can be found here and there are a few considerations that differ from this article, discussed here in more details.

Special thanks to Michael Tapes from Lens Align, who facilitated with his valuable knowledge in camera adjustments and who designed the new Lens Align MkII device. Also thanks to Arthur Morris from BirdsAsArt, with whom I had many detailed discussions on how to best design the ideal workflow.

Introduction

First I will spend a few words on the newly developed Lens Align MkII device compared to the previous version, the discontinued Lens Align Pro (view the product details here).

The materials used for the new Lens Align MkII are light and made of a very durable and light polymer, which make the new device smaller and much lighter. (Old: 350gr, new 100gr). Secondly, the assembly is no longer mounted with screws, but with a slick tongue and groove system. This eliminates the need to have tools available to (dis)assemble the Lens Align device. Also, the ruler is now made of the same polymer, not made from iron and is in the new design mounted in a fixed position. Finally, the ruler has a better and finer contrast image, allowing for even finer adjustment evaluations.

The size and ease of assembly allow for easy packing: I will have this device in my camera bag all the time.

Preparation and Setup

Camera Settings

For your calibration efforts it is best to set your camera in the following modes:

  • Shooting Mode (AF/Drive): One Shot AF and Single Shot
  • AF Selection Point: Center
  • ISO Settings: as low as possible, ISO100 is ideal
  • Aperture as low as possible to achieve smallest depth of field
  • Live View Mode: on, set LV for ‘Stills’ and AF Mode to ‘Quick Mode’
  • Beep: on. This will generate an audible beep, when focus has been achieved.

The lensalign device is mounted on a tripod as well as your camera. The focus plane of the lensalign device must be paralleled with the camera focus plane.

Lens Align Distance to Camera

There are many theories about what the best distance of the Lens Align device to the camera is. Canon recommends 50x the focal length, which may be right for small lenses (for a 50mm lens you will calibrate at 2500mm = 2.5m), but quite unusable for supertele-lenses. For an 800mm lens this means 40meters ! At this distance the Lens Align device will be hard to read and atmospheric interferences will influence the accuracy of a focus sample. For me the following considerations work well:

  • Super Tele Lenses (from 400-800mm): calibrate at 30x to 15x focal length. If you place the LA device at further distances (like 50 times focal length), atmospheric interferences could impact accurate evaluations.
  • Midrange Lenses (from 100-300mm): calibrate at 40x to 30x focal length
  • Small Lenses (from 24-85mm): calibrate at 50x to 30x focal length
  • Place the LA device as far as possible from the camera, where the LA device is still well readable in Live View mode. The reason for placing the LA device further away from the camara is that calibration errors at close range, will multiply at further distances. Also, corrections made at further distance will be more accurate than close range corrections.
  • Place the LA device at the distance you will mostly use your lens, or within the average range of usage.
  • Place the LA device at 2 to 4 times the minimum focus distance
  • When calibrating zoom lenses, calibrate at the largest focal length

To summarise the above considerations in a formula you could use the following function for calculating the LA device distance:

Function of distance (in meters) to focal length
where x is the focal length of your lens in mm and y is the distance, to place the LA device at.

Lens Align Device Alignment

Mount the Lens Align device on a tripod and roughly align the front plate parallel to the camera sensor. On the back of the new Lens Align device, there are two holes. If you position your eye closely to the hole on the right, you can see though, marked as ‘main target’ (see image below). Align the LA so that you can see the lens barrel that you mounted on your camera tripod.

PC

Make sure you have installed all components from your Canon Product CD, including the EOS Utility. I have setup my PC’s such that when I connect my camera to my PC, this is the utility that pops up first. If this is not the case, you can always start this utility manually.
See image below.

When the EOS Utility window comes up, select “Camera Settings/Remote Shooting” and in the next window select “Life View Shoot”. When selecting the “Life View Shoot” button, the PC connects to the camera and displays the “Life View Mode” from the camera to the PC.

Make sure your life view mode in the application is set to “Quick Mode”, allowing your camera to focus fast(er) when acquiring a shooting solution.

Place the ‘center’ focus button on the focus plane of the lensalign device and let the camera focus on the lensalign device: wait for the beep to be confirmed that focus was successful: don’t take a photo (pressing the shutter button halfway or just use the AF-ON button). Return to the EOS Utility on your PC and zoom into the image you just focused.

IMPORTANT: if your camera does not show the live view on the back display, you need to press the Live View button on the camera to activate the back screen. If you don’t, the EOS Utility will completely control your camera and you won’t be able to adjust or set focus using the camera.

Using the zoom button, you can now have a closeup view of your focus solution and evaluate how well the camera focuses
With the dials displayed here (found in the ‘Focus’ pane of the EOS Utility application), you can now fine-tune focus the acquired image. Each single click in the focus pane, corresponds with the amount of micro adjustments you will have to apply in the camera microadjustment menu, see later.

With the ruler, you can see exactly where your camera found focus. Important is to make sure that the numbers above ’0′ are as much in or out of focus as the numbers below the ’0′ line.

Now that you have created a focused ‘Live View’ image on the camera and PC, with the knowledge of how many clicks in plus or minus, we now go to the camera’s microadjustment settings function. You can find that in the custom settings of you camera (xxD or xD models only): C.FnIII (Autofocus/Drive)->AF Microadjustment->Adjust By Lens. Enter the amount of clicks you entered in “EOS Utility” in this menu.

In the image below you can see the menus you have to go through to get to the MicroAdjustment settings:

Repeat the focus actions from above, until the ruler displays consistent focus results. Note: with each test run, dial the lens with the manual focus grip deliberately out of focus, so that the camera has to find a new focus solution.

Canon cameras can be (micro)adjusted with each lens individually: the camera will store the microadjustments for each lens individually. Note that any given lens with a 1.4TC or 2.0TC is a different lens as well.

Have fun.

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