Hand focusing a 50mm lens on a Camera

[Earl]

OH wow this is far harder than I thought, any tips?

 

this is my best effort so far

[Same old newbie alert]

Bahtinov mask, you can buy one or make one yourself

[PeterCPC]

I just use live view and magnify image - then just adjust until bright star is as small as I can get it. Use a high ISO.

[Alien 13]

Getting accurate focus will depend somewhat on the lens you are using, the old nifty fifty had a very sloppy focus ring that was almost impossible to set so shooting something distant in the daytime using AF with the lens wide open then taping it down and reducing it to between f 4-5.6 for AP at night can be a valid option.

If the lens is the STM version then you have a much more responsive and accurate focus ring so I would use the method similar to what Peter mentioned but instead of the brightest stars in the FOV I would concentrate on the very dimmest which will blink on and off with the slightest adjustment, be aware any dim stars will not show at all if the focus is way off.

Alan

Edited February 13, 2022 by Alien 13

[ollypenrice]

Is the problem one of identifying critical focus or of moving the focus ring with sufficient sensitivity to find and sustain it? Or is it both? Telescope Service do this gadget but it would be easy to improvise something along the same lines.

All you need is a ring with a protrusion from it fastened round the focus ring. The protrusion is pushed by a bolt at right angles to it. In the device above there is an opposed bolt to push the protrusion the other way but it might be easier to dispense with this and have a spring or rubber band pushing or pulling the protrusion up against the bolt. I used a spring on my very effective Tak microfocuser.

Once you have fine control like this, the 'vanishing small stars test' is probably as good as any.

Olly

[alacant]

2 hours ago, Earl said:

any tips?

Hi

Modern lens? Autofocus on the moon then switch the lens to manual.

HTH

Edited February 13, 2022 by alacant

[bottletopburly]

You can Autofocus a canon camera/ lens using APT if your connected to a pc