Using manual focus lenses on electronic Nikon film cameras with manual focus confirmation. What do you trust more?

albireo · Jul 3, 2023

This is a question for people who use Nikon autofocus film cameras with manual focus lenses. Eg

Nikon F4
Nikon F90X
Nikon F801S
etc

The cameras above about all have autofocus, but can be used with Ai-s lenses, or other manual focus lenses.

One can then focus 'by eye' (trying to achieve peak sharpness visually on the focusing screen) or via the 'focus confirmation' gauge in the viewfinder display (which usually works by displaying the symbols >,< or 'o' for focus achieved).

I'm having an issue with an F801s and a 35mm Ai-s whereby the two focusing methods do not match. I'm pretty sure that when I reach peak sharpness via the focusing screen, the focus aid indication is not at 'O'. If I tweak the focus so that the focus aid indication is at 'O', the image will be ever so slightly blurry on the screen.

What gives? Issue with lens? Issue with camera (mirror box out of alignment)? Normal tolerances?

Importantly, what would you trust? What you see on the focusing screen or what the focusing aid tells you? Thanks!

Sirius Glass · Jul 3, 2023

I can focus the two AIS lenses and manual PC lenses by eye, but then they are respectively 15mm 110 degree wide wide angle lens, 16mm Fisheye and the 28mm PC lens. All of them are of wide angle persuasion so of course they are easy to manual focus. I have the Tamron 150mm to 600mm lens which auto focuses well, but when used with the compatible 2X must be manually focused and it focuses easily because manually the focus pops in and out sharply. The Tamron 150mm to 600mm lens which auto focuses well with or with out the compatible 2X expended only on the Z cameras, not on film cameras.

madNbad · Jul 3, 2023

When I owned a Df, all the lenses used on it were chipped Ai-S. I had a replacement focusing screen but relied on the conformation dot. It may be worth a roll of film to see if the focus is better with the screen or the dot.

ic-racer · Jul 3, 2023

I'm having an issue with an F801s and a 35mm Ai-s whereby the two focusing methods do not match

You camera may be out of adjustment. What does the film "say" about the issue?

Alan9940 · Jul 3, 2023

I use MF lenses on my F4 all the time and, with my old eyes, I really rely on that focus confirmation light; especially with wide angle lenses.

albireo · Jul 3, 2023

ic-racer said:
You camera may be out of adjustment. What does the film "say" about the issue?

You are the winner. It is it in fact the camera. It was an easy one. I swapped it with my other Nikon AF camera. Same lens. With this camera, visual focus and focus aid match perfectly.

So something is out of alignment in my F801s. Perhaps with age the springs holding the mirror in place tend to lose tension resulting in tiny shifts? Perhaps the electronic focus aid is off instead. Will have to test with film. Interesting that this can happen. Would be interested in opinions on the matter and whether there's any way to rectify this mismatch. It's quite annoying.

250swb · Jul 3, 2023

albireo said:
Importantly, what would you trust?

What the results tell you is often a pretty good indicator.

Paul Howell · Jul 3, 2023

I use AI and AIS on my F4, when shooting in a hurry I just go by eye, when I have the time I prefer focus confirmation.

RalphLambrecht · Jul 3, 2023

albireo said:
This is a question for people who use Nikon autofocus film cameras with manual focus lenses. Eg

Nikon F4
Nikon F90X
Nikon F801S
etc

The cameras above about all have autofocus, but can be used with Ai-s lenses, or other manual focus lenses.

One can then focus 'by eye' (trying to achieve peak sharpness visually on the focusing screen) or via the 'focus confirmation' gauge in the viewfinder display (which usually works by displaying the symbols >,< or 'o' for focus achieved).

I'm having an issue with an F801s and a 35mm Ai-s whereby the two focusing methods do not match. I'm pretty sure that when I reach peak sharpness via the focusing screen, the focus aid indication is not at 'O'. If I tweak the focus so that the focus aid indication is at 'O', the image will be ever so slightly blurry on the screen.

What gives? Issue with lens? Issue with camera (mirror box out of alignment)? Normal tolerances?

Importantly, what would you trust? What you see on the focusing screen or what the focusing aid tells you? Thanks!

I would trust the AF aid; no doubt. It equals Nikon's AF calculations and they've never let me down

ic-racer · Jul 3, 2023

To fix your camera, there is usually an adjustment on the secondary mirror and a software adjustment, but I believe the Rollei Hy6 is the only film camera in which the focus point can be adjusted in the camera without additional software.

Sirius Glass · Jul 3, 2023

Sirius Glass said:
I can focus the two AIS lenses and manual PC lenses by eye, but then they are respectively 15mm 110 degree wide wide angle lens, 16mm Fisheye and the 28mm PC lens. All of them are of wide angle persuasion so of course they are easy to manual focus. I have the Tamron 150mm to 600mm lens which auto focuses well, but when used with the compatible 2X must be manually focused and it focuses easily because manually the focus pops in and out sharply. The Tamron 150mm to 600mm lens which auto focuses well with or with out the compatible 2X expended only on the Z cameras, not on film cameras.

RalphLambrecht said:
I would trust the AF aid; no doubt. It equals Nikon's AF calculations and they've never let me down

I trust and use the AF with the lenses that have it.

Craig · Jul 3, 2023

Does the F801 have an interchangeable focusing screen? Could the screen not be seated correctly, or be the wrong one for the camera?

In the F4/F6 I have never had the focus confirmation be wrong.

benveniste · Jul 3, 2023

albireo said:
I'm having an issue with an F801s and a 35mm Ai-s whereby the two focusing methods do not match. I'm pretty sure that when I reach peak sharpness via the focusing screen, the focus aid indication is not at 'O'. If I tweak the focus so that the focus aid indication is at 'O', the image will be ever so slightly blurry on the screen.

Apologies in advance for the obvious question, but are you using an eyepiece which matches your vision?

albireo said:
What gives? Issue with lens? Issue with camera (mirror box out of alignment)? Normal tolerances?

The mirror box being out of true or the focusing screen being incorrectly seated could cause it as well.

albireo said:
Importantly, what would you trust? What you see on the focusing screen or what the focusing aid tells you? Thanks!

I trust results. Shoot a test roll both ways wipe open, preferably with multiple lenses. Then scan the negatives/slides.

With manual focus lenses, I found that I trusted the focus aids on my Nikon FA slightly more than the "green dot" of the F100.

albireo · Jul 4, 2023

250swb said:
What the results tell you is often a pretty good indicator.

I have my last roll ever of Adox Silvermax loaded in camera. I discovered the issue afterwards. Would be nice if possible to have some pictures in focus.

albireo · Jul 4, 2023

benveniste said:
Apologies in advance for the obvious question, but are you using an eyepiece which matches your vision?

benveniste said:
The mirror box being out of true or the focusing screen being incorrectly seated could cause it as well.

Thanks. No eyepiece. Good idea about the focusing screen. I poked it and it won't budge or move at all - perhaps the whole prism assembly has moved slightly.

ph · Jul 4, 2023

Apparati designed for autofocus do not usually have screens particularly usable for manual focus rather than framing the motive.

Canon for example offered a manual focussing screen for their 5d series.

In my experience manually focussing the Nikon Z is very much preferable to its autofocus if you wish to decide yourself on exactly where to place the focus. This requires that the focussing-enlargement and spot-metering point stays where you wish it to be.

The manual focus of the digital Nikon Z is especially useful with stopped down lenses since the light amplification of the viewfinder makes any motive visible (and one does not have to depend on a usdeless screen which is invisible in sunlight)

p.

Paul Howell · Jul 4, 2023

I replaced the standard focusing screen on my Pentax SF1 with a salvaged split image screen from a Miranda EE, the SF1 has interchangeable screen, all I had to do was cut the Miranda Screen to fit with a Dirmal grinder attachment . There were also after market split image screen made for various AF bodies.

benveniste · Jul 4, 2023

albireo said:
Thanks. No eyepiece. Good idea about the focusing screen. I poked it and it won't budge or move at all - perhaps the whole prism assembly has moved slightly.

IIRC, without an eyepiece Nikon cameras of that era had a built-in 1 diopter offset, so if you have perfect vision the view in the finder will appear off to you.

ic-racer · Jul 4, 2023

Autofocus digital cameras (except for the rare digital SLR) have focus systems with nothing in common with a film camera autofocus SLR that the OP has (as diagrammed below).

CMoore · Jul 5, 2023

Alan9940 said:
I use MF lenses on my F4 all the time and, with my old eyes, I really rely on that focus confirmation light; especially with wide angle lenses.

Pardon my ignorance, all my cameras are MF only.

Is that common with most AF 35mm SLR.?
They have an "in focus" alert, even when using a MF lens.
That could be convenient.

Alan9940 · Jul 6, 2023

CMoore said:
Pardon my ignorance, all my cameras are MF only.

Is that common with most AF 35mm SLR.?
They have an "in focus" alert, even when using a MF lens.
That could be convenient.

I can only speak to the two AF 35mm cameras I own--Nikon F4 and Nikon N90--but both have a focus confirmation light.

reddesert · Jul 6, 2023

benveniste said:
IIRC, without an eyepiece Nikon cameras of that era had a built-in 1 diopter offset, so if you have perfect vision the view in the finder will appear off to you.

The -1 diopter of the default Nikon SLR eyepiece means that it presents an image that appears as if it were 1 meter away (most viewfinders, not just Nikon, do something like that). It works fine for people with normal vision. If you normally wear glasses then you can add a diopter, however this diopter compounds with the eyepiece, so that if you have a +4 prescription, then the eyepiece that Nikon labels "+4" isn't literally a +4 diopter. That's the confusing part, which maybe you were thinking of.

Later Nikon SLRs have a built-in diopter adjustment, which is useful (I think the N8008 does not). However, if one accidentally misadjusts that, then it will be hard to focus on the screen; I've done this where it's just far enough out of adjustment that I can still read the display but the image doesn't look right. Easy to correct once you recognize the issue.

JerseyDoug · Jul 6, 2023

For me it depends on the focal length of the lens. I can no longer focus my AI'd 28/3.5 Nikkor with my F's or by eye with my wife's F6. The only way I can use the lens at all is with the focus confirmation of the F6.

OTOH I can easily focus my AI'd 105/2.5 Nikkor by eye with any of my cameras and actually find the default F6 screen easier to use than either the K or the G2 screen of the F's. I do not bother using the focus confirmation with the F6.

My 50/1.4 and 55/2.8 Micro Nikkors are somewhere in the middle. It good light I can focus them by eye with any of the cameras. In poor light I am less confident and prefer to use the F6 and the focus confirmation. And I have never seen a disagreement between the two focusing methods.

chuckroast · Jul 6, 2023

albireo said:
This is a question for people who use Nikon autofocus film cameras with manual focus lenses. Eg

Nikon F4
Nikon F90X
Nikon F801S
etc

The cameras above about all have autofocus, but can be used with Ai-s lenses, or other manual focus lenses.

One can then focus 'by eye' (trying to achieve peak sharpness visually on the focusing screen) or via the 'focus confirmation' gauge in the viewfinder display (which usually works by displaying the symbols >,< or 'o' for focus achieved).

I'm having an issue with an F801s and a 35mm Ai-s whereby the two focusing methods do not match. I'm pretty sure that when I reach peak sharpness via the focusing screen, the focus aid indication is not at 'O'. If I tweak the focus so that the focus aid indication is at 'O', the image will be ever so slightly blurry on the screen.

What gives? Issue with lens? Issue with camera (mirror box out of alignment)? Normal tolerances?

Importantly, what would you trust? What you see on the focusing screen or what the focusing aid tells you? Thanks!

I use almost nothing but Ai and Ai-S lenses on my D-750 and have no issues focusing it at all. This includes a 20mm f/2.8, 24mm f/2.8, 35mm f/2.8, 50mm f/1.4, 85mm f/1.4, 105mm f/2.5, and a 180mm f/2.8. The manual lenses are dirt cheap (comparatively) an way beefer construction than the AF lenses. They are tack sharp and - best of all - I can carry both a film- and digital body when using them.

albireo · Jul 6, 2023

chuckroast said:
I use almost nothing but Ai and Ai-S lenses on my D-750 and have no issues focusing it at all. This includes a 20mm f/2.8, 24mm f/2.8, 35mm f/2.8, 50mm f/1.4, 85mm f/1.4, 105mm f/2.5, and a 180mm f/2.8. The manual lenses are dirt cheap (comparatively) an way beefer construction than the AF lenses. They are tack sharp and - best of all - I can carry both a film- and digital body when using them.

Chuck, thanks for the reply. I like those old Ai-s primes, too. Normally I have no issues focusing, but with this camera I'm experiencing a mismatch between what I see as being in focus and what the focus aid in the viewfinder tells me it's in focus. Turns out it's an issue with the camera. I have just developed a roll so I will know soon if correct focus is achieved by eye or by the focus aid.

Using manual focus lenses on electronic Nikon film cameras with manual focus confirmation. What do you trust more?

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