agillot

i have same lens but a 800 mm f8 on a D300.i just focus by eye , i made sure that the diopter ????? at the view finder is set right , need reading glasses to read , but dont use them on a camera . been using it for over 2 yrs now [ birds ] and rarely get out of focus .did take some practice .

olemikey Loc: 6 mile creek, Spacecoast Florida

Set up a static test, tabletop or tripod, good lighting, good detailed test subject, use timer, focus well..... practice with it, take out all the handheld variables, then you will know.

Al Beatty Loc: Boise, Idaho

I ran into a similar problem with my D750 and an old lens. I found I need to adjust the "diopter" (I think that's what it's called) on the eyepiece so I could better see what I was focusing on. Just a thought. Take care & ...

CHG_CANON Loc: the Windy City

Your situation may be different than mine, but I just can't 'see' good enough to manually focus a lens with the old-style SLR / DSLR view finder. Give me a focus assist like the LiveView zoom or the EVF zoom, and I can 'see' the details and focus manually as good as the camera in auto-focus. Otherwise, it needs to be AF for my eyes.

photoman43

Ditto the above. I have used Nikon manual focus lenses often on Nikon DSLRs. You need to focus very carefully and need to have a very stable shooting platform like a tripod, ball head, bean bag, etc.

photog11 Loc: San Francisco

Thank you camerapapi. Your answer is just what I was looking for.

photog11 Loc: San Francisco

I am afraid the combination of lack of technique and bad eyesight is condemning me also to autofocus.

amfoto1 Loc: San Jose, Calif. USA

1. Your first sample shot appears to be entirely soft. Even though you used a reasonably fast shutter speed (1/1250), that could be due to camera shake blur.

2. The second shot of the three pelicans is actually reasonably sharp and in focus. It may be about as good as you can expect from a lens that age.

3. Third shot appears to be reasonably sharp closer (look at the closest birds in the water), but soft in the middle distance to infinity. It simply appears that you weren't focused to infinity. This also could be an atmospheric effect, which may have made matters worse, or might even nothing to do with the lens.

You should try a more formal test of the lens. Put everything on a tripod, aim at a detailed, flat subject like a weathered fence or brick wall, line up so that the camera's sensor plane is as parallel to the flat target as possible. Now lock the mirror up or use Live View (which also raises the mirror), focus very carefully and take one or two test shots. Use a remote release (or the self timer) so that you aren't touching the camera when the shutter trips. Live View also may allow you to "zoom in" on the preview to see if you are focused accurately. Try this at different apertures. It's quite possible the lens is sharper at some f-stops than at other. (All your test shots appear to be done at f/8, if the image EXIF is to be believed.)

If you have a filter on the lens, remove it and try without. Depending upon the quality of the filter, some of them can have a pretty nasty effect on image quality.

Basically, with tests like this you try to eliminate everything else that might effect image sharpness, so you're truly only testing the lens sharpness when focused. Obviously you won't be able to use these "ideal" focusing methods with active subjects, especially fast moving, difficult ones like birds in flight! Those are about the toughest type of subject to focus manually.

If you see a lot of variability in focus accuracy in your test shots, it may be wear in the lens focusing mechanism. I don't see any variation in sharpness across the image frame in your samples. So I wouldn't suspect a problem like a de-centered element. That usually shows up as part of the image soft while other parts are sharp. Of course, these particular images might simply not show where there's a problem. Test shots like above will confirm whether or not there is any problem like this.

I do see some significant chromatic aberration in the three pelican image (didn't look that closely to the other two images, it may be in them, too). It's mostly off-center... most prominent in the bird's wings nearest the edges of the images. This may simply be the nature of the lens and isn't uncommon in telephotos (modern ones often use super low dispersion and fluorite elements to reduce chromatic aberration.... I would guess a lens that age uses neither).

I hope you don't mind.... I tried sharpening the three pelican image in Photoshop, as well as some work to reduce the chromatic aberration in it... To me it looks pretty good up to 66% or maybe a little more. Maybe more could be done if working from the original image, rather than this JPEG. See what you think...

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photog11 Loc: San Francisco

Thanks Alan. Your thoughtful comments and suggestions are much appreciated.

rfmaude41 Loc: Lancaster, Texas (DFW area)

For a different approach, Change out the (focusing) screen for a split image (45 degree diagonal) screen. I've done that with all of my film and digital cameras; makes it much easier (and efficient) to focus correctly.

imagemeister Loc: mid east Florida

You should have "splurged" a $100 more and got the ED IF version of the 300 AIS. ....! The version you have was never noted as being very good on digital ! - is why it is $100 - As mentioned, these manual focus lenses work best with a mirrorless body and focus peaking.
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imagemeister Loc: mid east Florida

photoman43

if you decide to get a 300mm AF, consider the Nikon AF-S NIKKOR 300mm f/4E PF ED VR Lens. The pf version is sharp and very light.

Quixdraw Loc: x

Nippon Kogaku Nikkor P Auto 4.5 300mm, AI ed by John White of AI Conversions. On the D 750.
Unfortunately, the Rock Doves that drew me out had left, so no opportunity for BIF or other wildlife. Various distances, hand held. The Focus indicator worked easily, generally focus was apparent, but I relied on the indicator for the purpose of this exercise. The last shot of a ridge several miles away. All SOOC. Must admit, was pleased with the performance of the old Warhorse and will have to give it more frequent outings. The light and atmospheric clarity are usually excellent here, and were this morning.

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Argus

Flip1948 mentioned the non cpu lens issue and I hope to clarify as I do this with a number of old lenses.

In the Set up menu (should be the wrench icon) you will find the Non CPU lens option. Select a bank number (1-9) to enter the lens info.

It will ask for focal length in mm as well as maximum aperture.

Once these are entered and saved the camera CPU has a better idea of what it is working with and will meter and focus a bit better than with no data.

Older AI-S lenses work best and then AI only. See if this helps as it is a good lens and it might need some fine tuning on the focus which also can be done in the menus. It helps to have a good accurate yardstick and a focus target to verify during the process. Good luck and I hope this helps.