Dumb question about AF Nikkor 75-300 lens

[MattNQ]

I have a really dumb question about an AF Nikkor 75-300mm 1:4.5-5.6 (japan) I picked up from cash converters for the princely sum of $40.
It is not pristine, but takes great sports shots.

I have a Nikon D3000 so of course it won't autofocus this lens. But I cannot seem to manually focus it on what I want at full extension at 300mm.

Am I correct in assuming that this problem is simply the aperture limits of the lens - I am optimistically trying to shoot too far beyond the distance that the aperture will allow the lens to bring clearly into focus?

Also, my bonus dumb question - what does the slider marked "full" and "limit" do?


Matt

[jim]

Move the slider to "full" and you'll be able to focus right to infinity.

I'm not familiar with this particular lens, but "full/limit" controls allow you to restrict the range of focus on long lenses, so that the lens doesn't waste lots of time running right through its range trying to find focus. It speeds things up when you know everything you will be shooting is at more or less the same distance.

[Wayne]

Normally on Nikkor lenses, the limit switch will permit focus to infinity on either setting, it is close focus distance that the switch affects.

[fillum]

There are no dumb questions Matt. (Well ok, there is one: "What model Canon should I buy?" :lol:)

I don't know if the limit switch affects manual focus, but do as Jim suggests and set it to "Full" anyway.

Your lens will have a minimum focus distance which will probably be around a couple of metres or so - you won't be able to focus on anything closer than that. However you should be able to focus manually at any focal length (75mm --> 300mm) on an object that is any distance further away than the minimum focus distance. If you can't focus there may be a problem with the lens.


Am I correct in assuming that this problem is simply the aperture limits of the lens - I am optimistically trying to shoot too far beyond the distance that the aperture will allow the lens to bring clearly into focus?Not sure if you're confused here or I'm misunderstanding the question. Aperture won't have any affect on distances at which you can focus. Aperture affects how much of the scene in front of your subject and behind your subject is in "acceptable" focus, but you should be able to focus on an object at any aperture regardless of distance (beyond the minimum focus distance of course). Aperture can affect how sharp the focus is - generally a lens is sharpest a stop or two down from wide open (so maybe f/8 or f/11 on your lens) - but you should be able to get reasonable focus at any aperture although might be a bit 'soft' at some apertures. (Hope that made sense).


Cheers.

[I @ M]

As the others above have said, the aperture should not affect focus and the "limit" switch should be set to "full" so to set this lens up for your camera it should be simply a matter of the basic steps.

#1 Make sure that the aperture ring is turned so that the orange 32 is aligned with the orange dot on the body and then lock it there with the sliding tab with the white dot.

#2 Set the limiter to full and make sure that the focus ring moves all the way through the distance scale on the lens.

This photo (http://www.photosynthesis.co.nz/nikon/af75300.jpg) shows all the necessary bits.

[MattNQ]

Thanks all for your advice.
The camera won't let me take photos unless the orange 32 on the aperture ring is aligned with the green dot - doesn't like it on the orange dot.
Possibly just the limitation of the D3000 using the old lens?

I probably am getting confused on the aperture effect.
Easiest way to explain my problem is to show some examples.

First image came out ok. Taken from about 30m away, 1/1600, F/6.3, 175mm focal length. subject is in focus

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Second image. Taken from about 70m away. 1/1250, F/5.6, 270mm focal length. I couldn't bring the athletes into focus at infinity, but the advertising boards are focused ?? That is why I thought it was aperture related - a depth of field problem.
I am assuming I am doing something wrong?

74404

[jim]

If you can set it to infinity but it won't focus there, it's probably broken.

[MattNQ]

After reading the thread by Lostris about the 18-200 lens not focussing at infinity, a lightbulb popped up over my head.
I hadn't thought to check the lens elements. They didn't feel noticeably loose.

But sure enough, the final element had unscrewed a bit.

Everything is now tight, and the results are much better

This one is handheld at the full 300mm from across the field

77581

This one is at 165mm

77580

Now I'm getting my $40 worth!

[darrenmars]

much better results! I hadn't heard of this loose-final-element thing before. good to see you're getting your money's worth