# Manual focus on a Nikon D90



## abhishekdg (May 20, 2012)

Hi,

I have a Nikon D90 and the only lens is the 35 mm f 1.8 g prime. Now I am trying to learn manual focus on the D90 and can do so when when I turn the little knob on the side to M and wait for the blinking green dot in the viewfinder to be static. However this works when there's enough light.

Question is how do you manually focus on your subject when its dark?The green dot keeps on blinking and it never turns static. 
Also how do you focus to infinity on a 35mm lens when you are trying to do night photography?


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## KmH (May 20, 2012)

You can just shine a flashlight on your point of focus until the green in-focus indicator stays lit. Then turn off the flashlight and take your shot.

Or you can turn on the Auto Focus Assist feature, achieve auto focus, and then move the D90 focus mode switch to manual.

Unfortunately, with the advent of auto focus, many focusing aids that used to be standard features of cameras and lenses - like distance indicator scales - are no longer included. Particularly with the inexpensive consumer grade lenses like the AF-S 35 mm f/1.8.

Lenses also used to have DoF and hyperfocus indicator scales too.


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## abhishekdg (May 20, 2012)

Thanks to both of you for the info ..
Well i was trying to shoot ina very dark place where I wanted an exposure of 2 mins but couldn't focus on anything as it was really really pretty dark. Thought if I could set the focus to infinity but it seems not possible in a 35 mm lens.

The Katzeye option seems to be interesting..Maybe will try that out.


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## KmH (May 21, 2012)

You can set the focus to infinity on that lens but you have to do it by eye (trial and error).

As it is infinity focus has always been kind of a moving target because it's not a precisely defined number. Where 25 feet can be shown on a distance scale as a line on a scale, infinity is actually a range of distances, which is why it is shown with a symbol instead - &#8734;.

Plus some lenses can be focused past the practical for photography value of infinity, or focus just short of infinity.

You can use depth of field (DoF) to your advantaqe more effectively than you can infinity focus. DoF and focus are essentially the same thing. DoF determines how much of a scenes foreground and background is, or isn't, in focus.


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