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my sigma 150mm seems to have developed a bit of a focus issue today. this may or not be the result of several minor spills and a relatively big one today.

anyway...clumsiness aside, how do i check a lens for focussing ? is there some chart i can use and maybe test to see if i can fine tune it on the d300 ? if all else fails, where can i get it calibrated or tunes or whatever you call it ? any recommendations and how much is it likely to cost ?

I would like to know too!

http://focustestchart.com/chart.html

Rooz this chart and directions were all the rage when we all thought our D70 were backfocussing

I like the idea someone else posted recently. Rather than using a focusing chart on a 45º angle, they set up the camera on a focusing rail and shot something at 90º to the lens. They first shot it with AF and then with AF off, moved the camera backwards and/or forwards to see if focus improved or not. This seemed a better way to judge focus.

I'll see if I can find the thread.

My way is to put couple of Lego blocks, or anything that have identical sizes, along a ruler. Separate them at an angle with equal spacing, focus on the middle one and see how far are you off to the front/back of it. Making sure camera is level with the objects.

those charts can be mislleading if u dont set em up 100%, best is to just shoot normally and see if there are any glaring problems

thanks for the tips. i dont have the patience or attention to detail to do those chart tests. i know its misfocussing cos i can clearly see it taking a normal image. the focus point has shifted to the left of the centre. i was thinking of calibrating it with the d300 but the process is pretty difficult to follow and i think its just for back/ forward focussing.

what i'm after is actualy somewhere to take it to get it adjusted/ realigned or whatever it is that you call it.

Glen wrote:http://focustestchart.com/chart.html

Rooz this chart and directions were all the rage when we all thought our D70 were backfocussing
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Like the idea someone else published lately. Rather than using a concentrating graph on a 45º position, they set up the photographic camera on a concentrating railway and taken something at 90º to the contacts.