Online Camera Autofocus Test ? Is There One

[David]

I am now convinced that there is something amiss with the autofocus feature on my camera after months of blaming the kit lenses and doing everything I could to improve things (remote shutter, always using at tripod etc) but now I have a new Siggy lens and Im STILL getting soft focus results.

Is there an online site where you get advise on how to test the accuracy of the autofocus feature on a Canon 4OOD.


I bought the camera at WOW Sight and Sound a little over a year ago and Im sure my warranty is probably expired.- Who do I send it to 4 recalibration ? I live in BRISBANE

[ricktas]

There are few focus tests out there. Not specifically designed for the 400D, as all camera's basically use the same thing. AF, and a Lens.

Here is one that works for any camera, read the instructions carefully. : http://focustestchart.com/chart.html

[Kym]

These mount at 45degrees - similar idea.
http://pentaxdslrs.blogspot.com/2008/06/part-1-autofocus-adjustment-for-pentax.html

[arthurking83]

if you've ever used an allen key, calibration may be a lot easier than you think!

I noticed that my D300 had manual focus issues with all my MF lenses(as I usually don't MF with AF lenses), and that the rangefinder indicator was always indicating when focus was achieved when just behind the acceptable range of DOF.

So I searched as much info on the D300(which there was none and just used the info available for the D200, which is the same as the info available for the D70 :p

There are two stop screws with hex key heads(allen keys) and IIRC they are 1.5mm sized key heads(can;t be too sure, other than I bought a 20 piece allen key set, and the size I wanted wasn't there! :()
So I bought another specifically for the size I wanted.. at $2-3 or even $10 they come in handy for many things anyhow.

So with a quarter turn of the correct screw, the D300 now focuses much more accurately. That is, manual focus indication seems to be more spot on than it used to be, and that's confirmed using liveview.

If the 400D has liveview that;s the best way to determine exactly how accurate(or otherwise) your AF system is.
Apart from my Tamron 28-75, all my other lenses focus 99% accurately.
That is, AF on a target.. any target! Just makes sure the AF point(box) in the viewfinder is totally encompassed by that target so there is no chance for the AF to be seeing something elses.
Totally defocus the subject and then let the camera focus on it.
This is where liveview is so handy. Where you switch to liveview and zoom in as far as you can to see if the focus is accurate. You then switch the cam to MF and if you can achieve better focus than your camera can, most likely you will, but by how much is the question!!).

Without liveview, all you can really do for your own peace of mind, is to try one of the popular focus test charts, do it as exact as possible and see if that confirms any suspicion of back or front focusing.
What I did as well, was to use some small packs of sultanas, as that's all I had. Matchboxes or whatever as long as they are not too deep(but also not too thin!)
You place about 5 or 6 of them in a line, with the central box protruding forward, and then either side of it you have the next box placed just behind it but fully revealed. The thickness of the boxes should help top determine the extent of any focusing innacuracies.
so that is your set up should look like this


[][][][][] from front on ...


and like this



.....................[].........[]
.......................[].....[]
.........................[].[]
...........................[]
from above.

what you are looking for here is backfocus. If there is no clear area with sharp focus behind the central spot, then you have front focus. Reverse the boxes, so that the central one is behind the others.

Just make notes! remember pencil and paper?? :p always defocus before you retry an AF run, and try to do each aperture up to about f/5.6. Beyond that the depth of focus will probably kill af accuracy anyhow as there is a deeper dof.

Frame the scene so that you can see all the boxes, but get as close as you reasonably can without going to macro distances. That is, if you are testing an 18mm lens then having a lot of wasted periphery is of no consequence.. but don't get too close just to get all the boxes in frame.

Then once you determine if the camera focuses back or forward of the correct plane of focus and if you find the info on which af stop screw to adjust, and from there you should be able to make AF work better.

[hoffy]

I've used this one in the past:

http://www.northlight-images.co.uk/article_pages/cameras/1ds3_af_micoadjustment.html

It was designed specifically for the 1ds, but would work for any camera. It uses a slightly different process, Moire interference patterns. A bit trippy, but I have found it better then the old 45deg test.

[Miaow]

I might have to try those tests also - I often find that the focus seems be not right on with the 400D - It's helped actually using single centre point AF than multiple point AF (as was suggested at one of the recent meet ups when doing some bird pics) made it easier to get the focus exactly where I want it rather than one of the other points kicking in

Arthur - 400D doesn't have liveview unfortunately :/

[mcdesign]

Thanks for all this, I too have focusing problems, looks good on the monitor but when viewed on the computer not as sharp as I would like.