Using Lens Align to micro adjust lenses

[Julie Brown]

Hello All,

I am wondering how much of an advantage it is to use a device such as Lens Align to micro adjust my lenses? Any info you can provide is much appreciated!

[Doug West]

Also....if you don't mind Julie...another question?...

Is this just for the new cameras/lens? For example I'm using a 1DS Mark II.

Doug

[John Chardine]

Julie- I've used a home-made setup and LensAlign and the latter is nice to use but ultimately I am not sure you get any different results and therefore is it worth the money? Spyder has a simpler version available with a better price-point.

Doug- Only the newer bodies allow micro-adjustment of AF and I'm pretty sure the 1DsII doesn't.

[ericbowles]

I have the LensAlign product. If you are going to adjust the focus on your lenses using a micro adjust function, a tool like LensAlign is a necessity.

Virtually all cameras and lenses have some level of variation. LensRentals.com has several blog posts that talk about variation. Generally, variation is small and large focus errors mean a repair is needed rather than micro adjustment of focus. You also can have variation in both the camera and in lenses. Sometimes a camera is a little off - even if it is within spec. In that scenario all lenses would need an adjustment - or possibly there is no adjustment required as the lens error cancels the camera error.

If you are going to adjust focus, it works best on longer prime lenses than on zooms. Primes have a single focal length and the only issues involved is focus and alignment of lens elements. With zooms, you have compromises. Optimum focus might be achieved with one focal length, but that might throw off focus at other focal lengths. Most zoom lenses are a little soft at the extremes. Zooms that cover a wide range -like the Nikon 18-200 or 28-300 - have such a wide range of focal lengths and such complex lens formulas that micro adjustment normally is not appropriate. Generally you would optimize for the midpoint of a lens zoom range. The most successful adjustments tend to be with telephoto primes.

Focus adjustment requires two elements - a target for your camera to easily and consistently use for focus, and a scale to be able to understand the amount and direction of the focus error.

The target needs to be an easy target for the camera to recognize. You are not testing AF performance - you are calibrating. Different focus systems specify different types of targets, but you want a flat target that is perpendicular to the camera. If you were testing AF performance, you might choose angled targets or targets that would measure how well the camera acquires focus, but there is not a calibration for missed focus and LensAlign is not trying to test AF performance.

In your testing, it is critical that the focus plane is flat. If a camera is tilted very slightly, part of the image of your test target will be out of focus and it may incorrectly appear to need an adjustment. Lens Align uses a mirror to insure alignment of the camera with the target plane.

As you would expect, you need a tripod for your camera with a cable release. Mirror up is a good idea. Live View or similar functions are useful, but you need to keep in mind that some cameras use different focus technologies for Live View than for regular AF.

You want to shoot wide open at your widest aperture. This will not normally produce the sharpest image, but it provides the shallowest focus plane for your adjustment.

You want to use the focus tool at your normal shooting distance. Normally that is 25-50x the lens focal length. 25x provides a depth of field of about 2 inches on either side of the focus target - enough to see a difference on the scale.

LensAlign does not test for perfect focus. Your images may be a little soft and still provide the amount and direction of adjustment. Wide open is not necessarily optimum for sharpest images.

You should be able to test your lens a number of times and get the same result. Each test should "defocus" the lens and allow the camera and lens to acquire focus. If you have Live View, you should get the same answer on lens focus issues (but due to the use of two different focus systems, you might have small differences).

At the end of the day, adjustment of zoom lenses is unlikely to be needed. Long primes may need adjustment but it normally is small. Wide lenses typically have such a large depth of field that it does not really make a difference if you are off by an inch or so - and testing is very difficult with wide lenses.

[arash_hazeghi]

Lens align is not necessary you can use any target.

[Roger Clark]

While good advice above, I also agree one can use any target, but it does mean a little more experimenting. Then there is the question of how much does alignment change with temperature and/or temperature gradients or other conditions? So I test in the field on site where I'm photographing. I've outlined my method here: http://www.clarkvision.com/articles/microadjustment/

If you try this (or any method, also record the conditions of the test, including light level and temperature. John posted a potential difference in the amount of adjustment in bright versus low light conditions (any update on that John?). I've seen temperature effects (over large ranges, e.g. from 20 to 80 F). But I need to start recording conditions to see if there really is a pattern. For light level, simply record the exposure on a neutral scene. If temperature is changing, e.g. heating after sunrise, does that have any effect? Temperature gradients can affect image quality, distorting the shapes of lenses, but that is probably only an issue in unusual circumstances with the largest telephoto lenses.

Roger

[ericbowles]

I agree that you can use any target. The error I see repeated over and over is confusing calibration with auto focus accuracy.

For example, I've seen a number of posts of round objects or angled objects for focus testing. These are subjects that have focus errors under normal circumstances, so they are less reliable than flat subjects. Likewise the size of the focus target matters. You want a target that extends beyond the camera focus sensor to reduce or eliminate the change that the focus sensor does not perfectly match the sensor seen through the viewfinder.

Testing needs to isolate enough variables that you don't make things worse. Roger's comments about temperature are spot on - temperature effects can cause soft images even with calibrated gear.

My main caution is to go slowly with micro focus adjustment and make sure you use a robust methodology that avoids user error. It's a lot easier to create test images with missed focus than it is to create perfectly sharp test images.

[Ian Cassell]

Not to negate the great technical information already offered, I offer a purely practical observation ...

I have a Sigma 100-300mm f/4. Although a decent lens, I was always underwhelmed with it's sharpness. Using Lens Align, I did a MA on my 7D and found it needed signficant adjustment (~ -9). I am now MUCH happier with the lens.

[Steve Uffman]

I am with Ian on this one.....I did my 500 and my zooms and all seemed improved...did each lens with each body
(7d and 5d), TC and lens combo ....

First discovered the problem when my wife and I were in Galapagos...we both took images of a pintail duckling swimming in front of the hen....Her duckling was spot on..duckling sharp, hen less so as should have been based on the aperture.....mine, shooting with the focus point on the duckling was duckling soft, hen sharp...since adjustments all images are much better....On my 7D, I had similar magnitude adjustments as Ian...Much happier and confident now

[Julie Brown]

Lots of good information here. Thanks to all of you for taking the time to reply to this thread. I have had some problems lately with IQ and focus in both heat and humidity as well as in cold temperatures.

With a bird photography trip in less than two weeks, I want my gear to perform optimally.