Lens Calibration

Modern DSLR are techno-marvels, mini computers with a sensor for optic nerve. On it’s own that sensor isn’t much good without an eye.
In order to see your camera needs a lens, an eye for your optic nerve.
The higher quality your lens the better you see, but even the best lens might not focus where it should.
So many modern DSLR allow for autofocus micro-adjustment.

This is important to professional photographers as we need the sharpest cleanest images from our gear. It’s just one more step of care and maintenace you should expect from a professional.

Two years ago I made my own target and performed a few calibrations. It worked well, but it wasn’t a very durable target.

Two days ago I got a commercially made target, bit pricey for what it is, but should prove to be a bit more durable.

I bought a datacolor SpyderLENSCAL .
Here is how I use the calibration tool.

 

Place on a level surface, desk, bookshelf, or attach to stand

SpyderLENSCAL Lens Calibration

Select the camera and lenses you want to calibrate
For this sample I will show the steps for the Canon 5Diii – refer to your camera manual for specific micro-adjustments.

Turn on autofocus
Turn OFF image stabalization.
Set camera in Manual mode.

Set to the widest aperture of the lens (lowest number, F1.2, F2.8, F4 etc) to achieve the shallowest depth of field for each lens.
The when possible set to lowest ISO (100 or 200) to achieve the sharpest image.

Mount camera on tripod at the same height as the target and so that the sensor plane is parallel to the target.
Camera should be level.

5Diii Level

Now the next step — well the SpyderLENSCAL had no instructions so maybe you can find something on this
But in the past I have positioned camera 25 times the maximum focal distance.
eg- Canon 24-105L  f4 –  105mm X 25 = 2625mm = 2.62m
The target and the camera should be approximately 2.62m apart when calibrating AF.

Alternatively choose a distance that approximates the usual distance you use your lens.

Alright now focus on the target, and take an image.
Mess up the focus and repeat, then get a third.

Zoom in on LCD and check scale- If it looks out adjust.
If you can’t tell upload and check on your computer.

This sample is with my 85mm – pretty close but it is slightly back focusing.
You can tell this by looking at the ruler- the 0 is crisp, but the 1 to the back is crisper than the 1 at the front.
f/1.2 is a very shallow depth so I used it for the sample, f/4 is much harder to tell.
The idea is to have the -0- tack sharp with sharpness equal on either side of the scale.

Steps to adjust Microfocusing.

These are the steps for a 5Diii – please consult your camera manual for your camera.

On the 5Diii it is found on the AF5 menu

Press SET

Scroll to Adjust by lens

The first time you connect the lens with this feature you should press INFO to register the lens
after the first time pressing info allows changes.
Press INFO

On zooms like the 24-70 in sample, you will have the option to adjust the wide end (24) and the telephoto end (70).
Press SET

Move the cursor towrds the mountains if the lens is front focusing. Or like my 85mm sample above, move it towrds the camera to correct back focusing.
Press SET to accept
Press SET to modify Tele

Press SET to acceept
Then press MENU to return

Take another image of your target.
Mess up the focus and repeat, then get a third.
Check your images on the LCD screen

There you go, Bang on.

This was by moving the cursor 1 spot towards the camera.

If you don’t get consistent focusing results you may have to send the lens in for repair.

Please also note EACH camera needs to be calibrated for each lens. If your studio has two 24-70 2.8 lenses each will need to be calibrated seperately.

Hope this was of some help.

For consistant image quality calibrate your lenses monthly. Even weekly when in heavy use.