Is backfocus or poor focus a "thing" on Nikon's 35mm?

firemachine69 · Nov 2, 2019

jimjm said:
Your second photo doesn't necessarily appear like your subject is out-of-focus, although the image has a softer look, to my eye. You're using 2 different films here, in different lighting conditions, so that may be a large part of the reason. I think your second photo is great - it has a classic look to it.

I'd load the same type of film in both cameras, and shoot the same subjects with the same lenses then do a side-by-side comparison of the scans. I've owned over 30 Nikon bodies, MF and AF, and have never attributed any focus issues to the camera or lens. It was either my error, or the AF system focused on a different point than I intended, which only occurred with moving subjects on older AF bodies. I've found the F100 AF to be extremely accurate even for sports photography.

Well that's just it. I find that for whatever reason, the focus on the F100 "hunts" quite a bit more than the F75. I've gone back and forth, same lens and subject, and there's definitely more AF hunt on the F100. It's such an annoyance that my F100 is basically collecting dust, and I'm back to using my F75 exclusively.

cjbecker said:
It could possibly be a mirror out of alignment. Set your lens to infinity, choose something out at infinity to focus on. When you move the subject from the top to the bottom of the frame, Is it the same sharpness at the bottom and top? A mirror out of alignment will give a sharp at one and a out of focus for the other.

Just something else easy to try.

I'll give this a try tomorrow morning. Yay for late night shifts!

ic-racer said:
Is your F100 diopter correctly adjusted for your eyesight? If not this could cause your focus problems.

Yes, first thing I checked/adjusted.

At $250 USD to repair this, I would just have to toss out the camera.

Huss · Nov 2, 2019

Pioneer said:
Haven't you heard?

Nikons are nearly perfect. They never break and they certainly never have focus problems. If they do it is always user error.

Just ask any of the resident Nikon fanboys of whom many are present.

The focus on my F6 failed. It started to repeatedly front focus by enough to make the subject clearly out of focus. Nikon Los Angeles repaired it for about $250; they said they had to replace the electronic RF unit.
And that mine was not the first one they had seen..

FYI my F6 looked like new - so dings/donks/doings. Always cared for, never dropped.

firemachine69 · Nov 2, 2019

pentaxuser said:
Did you ever get the cause, firemachine 69, and what in the end did you decide based on our diverging comments?

pentaxuser

Besides the above, I've contacted the seller. The more I really inspect older photos, the more it's obvious there's a front-focus issue. Unfortunately I'm outside the 30 day window, but I won't be shy to leave the seller negative feedback if there isn't a satisfactory resolution.

I should have turned around and shipped it right back when I got it. The seller wrapped my F100 in a scratchy-fuzz scarf, wrapped with burlap on the outside.

And there was NO body cap on the camera. I just figured as it didn't have a CCD sensor, it wasn't that big of a deal. Perhaps I was wrong.

pentaxuser · Nov 2, 2019

firemachine 69, did you test the F100 lens on the F100 on the same shot as one taken with the F75 and its lens both cameras in autofocus. Then swapped the F100 lens to the F75 still on autofocus and taken the same scene again. Then tried the same thing on manual focus? That way you may get to the bottom of whether it is an autofocus problem with the F100 as well as eliminating the possibility of a problem with the F100 lens

You may have done some or all of the above but if not, it might be worth doing. It will either strengthen your case against the seller or not depending on what you find or it will at least get you closer to what is the cause.

Just some thoughts

pentaxuser

Huss · Nov 2, 2019

Use a blower to clean off any possible dust on your AF sensor. Especially seeing it was shipped w/o a body cap.

Sirius Glass · Nov 2, 2019

firemachine69 said:
Well that's just it. I find that for whatever reason, the focus on the F100 "hunts" quite a bit more than the F75. I've gone back and forth, same lens and subject, and there's definitely more AF hunt on the F100. It's such an annoyance that my F100 is basically collecting dust, and I'm back to using my F75 exclusively.

I'll give this a try tomorrow morning. Yay for late night shifts!

Yes, first thing I checked/adjusted.

At $250 USD to repair this, I would just have to toss out the camera.

I have never had the F100 focus hunting problem and I switch between the F100 and N75 frequently and regularly switch lenses.

reddesert · Nov 2, 2019

If you want to test whether a camera + lens has a focus error or focus shift, one way to do it is to place a yardstick at an oblique angle to the camera, so that one side is nearer and the other side farther. Focus on a known point, for example put the center of the yardstick in the center of the frame, make sure the camera is actually focused there, take image at a wide aperture. Do several tests with more than one lens. Then when you get the negatives/slides developed (or directly, with digital) examine whether the sharpest image is at the intended focus point.

This only works in the US. In the EU and most other places, you have to use a meter stick.

Stephen Schoof · Nov 5, 2019

I once had my F100's mirror box repaired by a local shop and when it came back the focus was off (focus in the viewfinder was different than focus on the film plane). I sent it to Nikon and they put everything back in proper alignment.

swchris · Nov 5, 2019

reddesert said:
This only works in the US. In the EU and most other places, you have to use a meter stick.

That's true. A yardstick won't work in Europe (with the exception of maybe UK).

Is backfocus or poor focus a "thing" on Nikon's 35mm?

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