Nikon F Photomic FTN Service

ic-racer · Jan 16, 2025

I just got a Nikon F with FTN finder. Also came with a 50mm 1.4 pre-AI lens and a 28mm pre-AI lens.

What caught my eye for the auction was the fact that the camera was in a case! Usually a pro in the 1970s would not carry the camera in a case. I thought, maybe this one has low milage.

Indeed, when it arrived it appeard to have never been taken apart before! I don't like dealing with other's mess, so I do seek cameras and other gear that have never been apart before.

mshchem · Jan 16, 2025

Iconic look. I would get it out of the case and let it air out.

ic-racer · Jan 16, 2025

Without even test firing the camera, the first thing, right out of the shipping box was to test the speeds.

I was quite impressed for a camera from 1969 that appears to have never been opened.

Expected Speed (1/Seconds)	Measured Speed (1/Seconds)	EV Error
1	0.8	-0.3
2	2.2	-0.2
4	4.2	-0.1
8	9	-0.2
15	15	0
30	32	-0.1
60	60	0
125	117	+0.1
250	244	0
500	408	+0.3
1000	1140	-0.2

ic-racer · Jan 16, 2025

Before tearing into the camera, I cleaned it to make an assessment if it was going to be a parts camera or a keeper.

After cleaning all the crud from the surface, it appears to be in fantastic condition. Certainly a keeper.

So this is worth finxing to keep. Here are some issues I want to address:

Dirty and hazy finder
Non-functioning meter
Back is loose
Finder is loose
Aperture arm bent
Deteriorating rubber mirror stop

Maybe more...

ic-racer · Jan 16, 2025

The battery compartment was clean and contained two dead cells without corrosion. How lucky is that!

Two new batteries of appropriate voltage were inserted and the meter works. The calibration is off and there is some foam inside that needs to be removed, so the next step is further disassembly.

AnselMortensen · Jan 16, 2025

That cleaned up nicely.
Nice score!

Andreas Thaler · Jan 16, 2025

My father bought a Nikon F Photomic Tn in Vienna in 1969.

Nobody understood what he was doing, because Nikon was not known here at the time. Instead a Miranda was recommended to him. But he was as stubborn as his son is today.

He used the F until the 1990s.

It accompanied us four Thalers on our camping trips through southern Europe, my father on his cave expeditions in the Austrian mountains, where he photographed underground domes and halls using the open flash method, on his mountain tours and in his work as a woodcarver, carpenter and artist.

In 1971, when I was five years old, I took my first photo with the Photomic Tn in Venice.

My father is no longer alive, but his Photomic Tn is in my closet. Still functional with minor damage.

A memory of my family, who unfortunately is no longer with me.

ic-racer · Jan 16, 2025

That is a nice story. When I was groing up my father's camera was an Argus C44. He kept it hidden so we could not play with it. (good thing because my brother and I dismantled everything in sight).

I now have the camera; it is on my list of cameras to restore.

BMbikerider · Jan 16, 2025

I wonder how many of the plastic wonders sold with the Nikon name (note - I did not say 'made' by Nikon) will be still soldiering on after 45 years? I have a very late Nikon F2a which truly it would possibly be described as Excl+++ by a dealer. No paint loss no scratches to the chrome. It has been checked and the meter and shutter speeds are all within Nikon's tolerances. Again it came to me with the bottom half of the original case so it has had an easy life.
I am very impressed how accurate the meter actually is.

F4U · Jan 17, 2025

2 new batteries were inserted, says the OP. Assuming the CdS cells are OK, the meter is now off in the under-exposure direction, due to the 1.55V of the new alkaline PX 625 batteries. Back in the day PX-625's were mercury at 1.35V with a flat discharge rate. What needs to be done is to fashion a small paper ring and a piece of folded aluminum foil spacer for a set of 357 silver batteries to go in there. Then re-calibrate the meter for 3V, instead of the original 2.7V of the original Mercury 625's. If the CdS cells are still good, the meter should operate aurately down to 1/2 hour before sundown at ASA 400. As for the discarge curve of the silver 357's, it's not like those nice 625 mercury's, but it's all we've got. It'll do.

Tel · Jan 17, 2025

F4U said:
2 new batteries were inserted, says the OP. Assuming the CdS cells are OK, the meter is now off in the under-exposure direction, due to the 1.55V of the new alkaline PX 625 batteries. Back in the day PX-625's were mercury at 1.35V with a flat discharge rate. What needs to be done is to fashion a small paper ring and a piece of folded aluminum foil spacer for a set of 357 silver batteries to go in there. Then re-calibrate the meter for 3V, instead of the original 2.7V of the original Mercury 625's. If the CdS cells are still good, the meter should operate aurately down to 1/2 hour before sundown at ASA 400. As for the discarge curve of the silver 357's, it's not like those nice 625 mercury's, but it's all we've got. It'll do.

Hard to tell from the photo, but those might well be Wein Cell zinc-oxide batteries

ic-racer · Jan 17, 2025

F4U said:
2 new batteries were inserted, says the OP. Assuming the CdS cells are OK, the meter is now off in the under-exposure direction, due to the 1.55V of the new alkaline PX 625 batteries. Back in the day PX-625's were mercury at 1.35V with a flat discharge rate. What needs to be done is to fashion a small paper ring and a piece of folded aluminum foil spacer for a set of 357 silver batteries to go in there. Then re-calibrate the meter for 3V, instead of the original 2.7V of the original Mercury 625's. If the CdS cells are still good, the meter should operate aurately down to 1/2 hour before sundown at ASA 400. As for the discarge curve of the silver 357's, it's not like those nice 625 mercury's, but it's all we've got. It'll do.

Not sure where you are getting those numbers as the battery volage for testing is 2.7v, which had not yet been posted. The meter teardown and calibration posts are coming soon...

ic-racer · Jan 17, 2025

Tel said:
Hard to tell from the photo, but those might well be Wein Cell zinc-oxide batteries

No, those cells are the originals that were found in the camera.

ic-racer · Jan 17, 2025

Opening the meter revealed deteriorating foam rubber that needs to be removed and replaced.

ic-racer · Jan 17, 2025

After cleaning, reassemble with new foam rubber. DeOxit was used to carefully clean the resistor element (red arrows).

ic-racer · Jan 17, 2025

Functional testing, as found, nothing adjusted.
Coupled 50mm f1.4 lens. Battery voltage 2.7v.

Light Source EV	Exposure Error EV
5	-3.5
6	-3.5
7	-3
8	-3
9	-3
10	-3
11	-3
12	-3
13	-2
14	-2
15	-2.5
16	off scale

ic-racer · Jan 17, 2025

Next test is stopped down. To properly do stopped down test, a lens without a claw needs to be mounted and the lever of the FTn finder needs to be pressed up to read "5.6" on the front scale. In this case a 50mm 1.8 AIs.

Light Source EV	Exposure Error EV
5	off scale
6	-3.5
7	-3.5
8	-4
9	-4
10	-3.5
11	-3
12	-2
13	-1.5
14	-1.5
15	-1.5
16	-1.5

ic-racer · Jan 17, 2025

The manual does not mention much about the neutral density filters, other than they can be stacked.
Unlike the body of the camera, the FTn finder had been previously disassembled. The filters were gone, thus explaining the high readings.

New filters were easily obtained from discarded negatives. I wound up using a density around 1.5 log D.

ic-racer · Jan 17, 2025

BTW, both the Tn and FTn service manuals should be acquired as the troubleshooting and calibration is mostly covered in the Tn service manual.

This is the schematic.

To achieve the best possible results I wound up jumping the R1 resistor to minimize error on the high side and setting Ro to the highest setting (near 1Meg) to improve the low end.

Unfortunatley my CDS cells passed too much current in the dark, and complete calibration of high and low could not be established. The middle (EV9) is established with the trimmer R2, visible on the top of the device after removing the cover. R1 and Ro require disassembly for each change. Actually in the manual it asks to jumper across R1 with an external resistor bank, then re-assemble the device for on-camera testing, to find the correct resistor (10 ohm to 80 ohm). Again, in my case I wound up using 0 ohm.

I did get a reasonably good compromise. Maybe some day I'd replace the CDS cells.

F4U · Jan 17, 2025

Looks like you don't me chiming in. Looks like you got this well under control. Well done.

ic-racer · Jan 17, 2025

F4U said:
Looks like you don't me chiming in. Looks like you got this well under control. Well done.

Actually I don't mind, just was clarifying to avoid confusion later. Plus there are more mysteries to be solved.

For testing zinc cells (675) with brass adapters.

ic-racer · Jan 17, 2025

l think I have done what I can for this finder with the existing CDS cells.

Final Testing:
ASA 100
K 14.03
R1 = 0 ohm
Ro = Max (1 meg)
ND = 1.5 log D
Lens = 50mm f1.4 Non-AI Nikkor
Batteries = zinc 675 with adapters, voltage 2.7V
R2 = adjusted to zero at EV 9 per Nikon Service Manual

ic-racer · Jan 17, 2025

Final results with the existing (bad) CDS cells. Probably useable. Still much better than the Nikon Fun Touch 6!

EV Light Source	Exposure Error EV
5	-2.3
6	-1.3
7	-0.6
8	-0.3
9	0
10	+0.3
11	+0.6
12	+1.3
13	+1.6
14	+2
15	+2
16	+2

F4U · Jan 17, 2025

That chart tells me the CdS cells are likely weak, which is what I feared. You can only adjust the meter for strong light or low light. There is no compromise.

ic-racer · Jan 17, 2025

F4U said:
That chart tells me the CdS cells are likely weak, which is what I feared. You can only adjust the meter for strong light or low light. There is no compromise.

Do you have experience replacing CDS cells? Finding some new CDS cells would be a good project. I all these years I have never replaced CDS cells. Thought about it, but never did it. I see DigiKey has a number of types available.

Nice thing in the FTn meter is the diaphragms, ND filters and lenses are separate from the CDS cell, so packaging is not as important.

Nikon F Photomic FTN Service

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