Nikon F2 Photomic DP-1 aperture not coupling properly

[nic_olas]

Hi all,

Hoping someone in the Nikon F2 know has some ideas on this one.

I just got a new (to me) Nikon F2 w DP1 and put a lens on, clicked it to smallest and largest aperture to tell the meter what to do. Looked in the finder and the aperture readout doesn't match at all. When set to f5.6 on lens it reads f22 in finder, f16 on lens reads as the largest aperture and a white circle. The lens readout won't go down lower than f5.6 even if the lens is @ f2

Meter needle moves so that shows power to the meter works, but doesn't seem accurate.

The prism was a bit beat up, could it have been knocked out of alignment inside?

Am I missing something in the setup, I hope there's a fix, it's a great camera.

Thanks!

[ben_hutcherson]

I'd remove the finder and play with coupling pin. You should be able to move it back and forth. If you can, get it back over to the center and push it up into the mirror head. You should hear a sort of springy click when you do that and see 5.6 appear in the window on the front. This "cocks" the mechanism to be re-indexed. In a normally functioning F2 prism(DP-1/DP-2/DP-3) or an F Photomic FTN this tends to happen automatically when you mount and index a lens, but the manual does describe the manual reset procedure.

To properly "follow" the prong on the lens, the pin needs to move both side to side and up and down so that it stays engaged with the lens. The whole assembly rides along a rail by a pair of rollers. The prong has a spring that pushes it down all the time, with its motion limited by an additional arched bar that keeps the pin extended the proper amount. The parts CAN get gummy with age, and in particular the up-down motion of the prong. It seems to happen more often IME with the F prisms than F2s but it can happen with them.

Unfortunately too from what I remember(and it's been a couple of years since I've been inside one) the mechanism isn't quite as easy to get to in F2 prism as it is in an F2 prism.

I use to pull these apart at the first sign of trouble and service the pin mechanism completely. What I'd always do is run all the moving/sliding parts through my watch cleaning machine and then put them back together with a sparing amount of watch mainspring grease(less is more-you don't want so much that you'll attract dust). All the ones I've serviced this way are still fine several years later. I realize I'm mentioning using tools and supplies that I have for other reasons, and used them because they were convenient and I knew appropriate for the job. In all honesty disassembly, cleaning in something light lighter fluid, and then using a light grease would probably be fine. Watch mainspring grease is expensive-if I didn't have it I'd probably use something like model train grease, which you should be able to get at any hobby shop, or even just a very light automotive grease(which is going to be the least expensive option of the above).

If you remove the visible screws on either side of the prism, the Nikon name plate should slide off and give you a good view of the mechanism(and access to it). Once you've done the test I've describe above, you can pull it off and probably get a better idea of what's going on. You MIGHT be able to get it working well enough without further disassembly by sparingly putting lighter fluid on the spring and sliding parts, working them up and down, and then again putting a tiny amount of grease on them.

[robert_bowring]

Follow what Ben says. These finders are not that complicated to take apart and clean. Just go slowly and carefully. Like he says use any lubricant very sparingly. Do not use any type of spray cleaner or lubricant. It will get everywhere and you will end up with a mess. A set of proper screwdrivers will make things easier. Those small crosshead screws are NOT Phillips head screws. Do not use a Phillips head screwdriver on them. You will need some JIS screwdrivers. I got mine from a company called Micro Tool. 

[nic_olas]

Thanks for the input. I felt confident this morning and opened up the prism. 

I could see the tiny aperture wheel that shows in the finder and links in with the aperture pin. 

Without removing any gears or pulling complex things apart I did the following:

1. Holding the aperture pin (rabbit ear pin) engaged at the widest f stop (1.2/1.4) 

2. Carefully turned the little aperture gear / wheel with the numbers to show the 1.2/1.4 mark

3. Let go of the aperture pin and reset to f5.6 

4. The mini gear with f numbers when reset matched f5.6

I gave everything a good blow with the air rocket to clean any dust before putting the 2 prism halves together, screwing it all back together and put on the F2.

Low and behold, the aperture on the lens matches in the finder!

Hope this helps anyone in the future with a similar issue. Photos attached.

It's a delicate but not super complex mission!

 

 

 

 

[nic_olas]

Next challenge will be to get the light meter to read accurately! 

[ben_hutcherson]

What you've accessed there is the ring resistor, which is the "brain" of the meter. This is a wear point and can cause inaccuracy, but my experience is that problems here more often result in a jumpy meter. If I'm there, I'll usually put a small drop of carbon tet(not recommended unless you know what you're doing, as it's quite toxic) and work the ring around.

What the rest of us were talking about is accessed through the front, and it's likely this will still need attention.

As for making it accurate-there are a couple of trim screws under the leatherette but they should be used with extreme caution. Ultimately, though, loss in accuracy probably comes from an aged CdS cell. Sover Wong and a few others can replace them. In all honesty, though, if the meter is still roughly linear but off by a stop or two, most of us I think just compensate with the ASA dial and call it good.

There's a reason I pretty much only use my F2SB(DP-3) and F2AS(DP-12) these days. Although they lack the "charm" of a moving needle, the silicon photocells seem to have held up better and they also use a different arrangement than the carbon ring resistor, You can see the in the dark, too, without needing the uncommon F2 prism light whose number escapes me.

[nic_olas]

20 minutes ago, ben_hutcherson said:

What you've accessed there is the ring resistor, which is the "brain" of the meter. This is a wear point and can cause inaccuracy, but my experience is that problems here more often result in a jumpy meter. If I'm there, I'll usually put a small drop of carbon tet(not recommended unless you know what you're doing, as it's quite toxic) and work the ring around.

What the rest of us were talking about is accessed through the front, and it's likely this will still need attention.

As for making it accurate-there are a couple of trim screws under the leatherette but they should be used with extreme caution. Ultimately, though, loss in accuracy probably comes from an aged CdS cell. Sover Wong and a few others can replace them. In all honesty, though, if the meter is still roughly linear but off by a stop or two, most of us I think just compensate with the ASA dial and call it good.

There's a reason I pretty much only use my F2SB(DP-3) and F2AS(DP-12) these days. Although they lack the "charm" of a moving needle, the silicon photocells seem to have held up better and they also use a different arrangement than the carbon ring resistor, You can see the in the dark, too, without needing the uncommon F2 prism light whose number escapes me.

Curious. The meter is quite jumpy, can you explain a bit more on remedying this?

Figure while I'm at it I'll do all I can to get this working well enough, if not back to 100%

Thanks for the reply!

[robert_bowring]

I adjusted my meter to agree with a meter that I know is accurate. You can then rotate the ASA dial to match the indicator arrow to whatever film you are using. There are 3 very small screws on the ASA dial. Carefully loosen those screws and you will be able to adjust the ASA dial. Be careful. Those screws are really small and easy to lose if you drop them. I have always wondered how they manufacture those small screws. Cleaning the resistor ring will usually cure the jumpiness. I usually clean them with a cotton swab or small paint brush with alcohol. Again, use the alcohol sparingly. Also make sure that the battery contacts are clean. 

[nic_olas]

9 hours ago, robert_bowring said:

I adjusted my meter to agree with a meter that I know is accurate. You can then rotate the ASA dial to match the indicator arrow to whatever film you are using. There are 3 very small screws on the ASA dial. Carefully loosen those screws and you will be able to adjust the ASA dial. Be careful. Those screws are really small and easy to lose if you drop them. I have always wondered how they manufacture those small screws. Cleaning the resistor ring will usually cure the jumpiness. I usually clean them with a cotton swab or small paint brush with alcohol. Again, use the alcohol sparingly. Also make sure that the battery contacts are clean. 

I'll give things a clean, will it likely be disassembling the internals to clean? 

Do you mean adjusting the asa by adjusting the little screws on the prism under the leatherette cover?

Which part is the resistor ring, if we're going off the photo above from the inside of the prism?

[robert_bowring]

It has been a while since I have worked on a F2 finder but I do not think you have to take it apart to clean the resistor ring. If I remember correctly the resistor ring rotates with the shutter speed dial. If you turn the shutter speed dial the resistor ring will turn also. No, I would not adjust those screws under the cover. The screws I am referring too are on the side of the ASA dial on top of the shutter speed dial. If you loosen those screws you can turn the ASA dial to line up the red indicator arrow. Just be sure to tighten those screws when you are done.

[ben_hutcherson]

If you look at your above photo, the ring resistor is the inside of the big toothed wheel. The copper piece touching it at 6:00 in your above photo is the contact you're concerned about in there. If you put a bit of cleaner(alcohol, lighter fluid, etc) on the ring and then turn the shutter speed dial back and forth to move the ring around you should at least clean it some.

It may not be perfect but should be less jumpy.

[nic_olas]

Thanks for all the feedback. Meter jump cured. I am now in a spot where I removed the asa cover to adjust the stops and correct, though I lifted and turned the Asa ring with the cover off and have no idea where baseline is to place the cover and align the Asa properly. Does it have a default position?

The concern is that the resistor ring inside will be all out whack and throw things off with the ASA not at a normal position. 
 

I actually have another DP1 and this meter reads accurate-ish in light but way way off in low light. Any ideas there?

I find I’m spending a lot of time tweaking the ASA back and forth to get these meters to match other camera readings. They’re always just a bit off.

The DP1s seem great and can use old NIKKORS so there’s a charm to getting it working well!

[bgelfand]

I did not have the F2, but I did have the FTn which I purchased in 1970. It worked well until the early 1990's when the meter began to give erroneous reading especially in low light. I took it to a very good camera repair shop in Sunnyvale. They took one look at it and said, "It's the ring resistor and we cannot get a new one." I called Nikon and they said the same thing. Sine at the time I took mostly black and white flas pictures, I bought a Gossen light meter, and continued to use it for a few years. I finally bit the bullet and purchased an F100.

Then while on the Internet, I came upon a post from a retired engineer who claimed to fix  Nikon FTn (and I believe F2) meters for a flat fee of $85. I called him. He told me the usual problem was not the ring resistor but the cells themselves; at the same time he would calibrate the Tn head for silver oxide batteries, since the original mercury batteries were not available. He sounded reasonable, so I packed up the Tn head and a check for $85 and shipped them off. 

A few weeks later, the Tn head was returned. I put silver oxide batteries in, mounted it on my F body. The reading from the camera agreed closely to the reading from the Gossen meter, and the F100; not perfect, but close. I bought a roll of Kodachrome and shot it under various lighting conditions. The resulting slides looked good to me.

The FTn continued to work until my home was burgled a few years later and the thief took it. 

The gentleman who repaired the meter was Robert Decker of Pleasant Grove, Utah. That was at least 25 years ago. 

[Zootman]

1 hour ago, bgelfand said:

The gentleman who repaired the meter was Robert Decker of Pleasant Grove, Utah. That was at least 25 years ago. 

I had Robert Decker repair an F2 Dp1 finder a number of years ago and it is still going strong.

[orsetto]

On 5/25/2023 at 8:24 AM, nic_olas said:

Meter jump cured. I am now in a spot where I removed the asa cover to adjust the stops and correct, though I lifted and turned the Asa ring with the cover off and have no idea where baseline is to place the cover and align the Asa properly. Does it have a default position?

When you refer to "cover", do you mean the little round black cap with the ASA numbers printed on it? If so, that should not have been removed: you should calibrate the ASA setting with it in place. The "home position" will have red arrow on ASA 100, with the numbers for ASA 6400  showing upside down, adjacent to the shutter release button at right, and parallel with the front edge of the camera top plate. You might simply have got off on the wrong foot: put everything back together, and start again as follows.

Use another known-good reference camera to meter a static scene. Note the aperture/shutter settings it indicates at a reference ISO/ASA like 100 or 400.

Aim your faulty F2 at the same scene using the same ASA/ISO setting, the same or similar focal length lens and the same framing. Note the aperture/shutter setting suggested by the F2 meter. Calculate how many stops deviation is shown. Say your reference camera reads 1/250th at f/4 and ISO 100 but your F2 reads 1/60th at f/4 and ISO 100: means your F2 mechanical ASA setting is overexposing by two stops.

This means you must pull up on the silver collar against spring tension, turn it so the red arrow points to ASA 25 instead of 100, and drop the collar back down to its locked position. The meter is then mechanically reset to match your reference camera, now all you need to do is correct the cosmetic dial indicator position by loosening the grub screws and turning the collar (without lifting) so the now-disconnected red arrow points to ASA 100 instead of ASA 25. Tighten the grub screws to reconnect the ASA collar to the spring-loaded ring resistor.. Your F2 meter should closely follow the readings of your reference camera at all ASA settings, unless the F2 has a significant defect impacting some part of its meter range (dead spot in resistor ring, failed CdS cell).

While this trick of altering the ASA indicator position is technically a quick n dirty hack that is frowned upon by professional repair techs, it generally works well as a long-term fix (I calibrated all of the F2 cameras I acquired between 1992 and 2012 in this manner, and they're all still spot-on). A professional tech might be more inclined to deeper adjustments like the trim pots under the prism leather: I do not recommend this route for DIY, as the trim pots are simply another ring resistor disaster waiting to happen. Tiny fragile carbon pots that haven't been moved for nearly 50 years should not be touched today: unless your F2 meter is off by an insane amount like six or seven stops that runs up against the hard limits of the ASA collar setting range, the collar indicator repositioning hack is far less risky and easily reversible.

Edited May 26, 2023 by orsetto

[orsetto]

Aaarrggghh! Just realized my attempt to help you with the ASA dial adjustment went off the rails: in trying to visualize the steps, I mis-stated what to do somewhere in the middle. Sorry for the error: ignore my earlier post and start again from here.

First, re-assemble everything you had taken apart, try to reposition the black ASA indicator cap to more-or-less its original position (red arrow on 100,  with ASA 6400 upside down on the right, parallel to the camera front edge).

Take reading with your known-good reference camera at ASA 100 (just an example, it can be any ASA you want). Note the settings the good camera suggests, say 1/250th at f/4.

Now, set your F2 ASA, aperture and shutter speed to match your good camera (i.e. 1/250th and f/4 at ASA 100). If your F2 meter disagrees significantly (needle display is not in the center notch), keep the F2 to your eye while lifting up the ASA collar against spring tension, and turn it in either direction until your F2 meter needle centers in the notch. Release the collar, and the mechanics of your F2 prism baseline ASA index are now adjusted to match the ASA of your reference camera.

However the red indicator arrow of your F2 ASA collar will now be pointing at an "incorrect" ASA number. So you must now loosen the collar grub screws to defeat the collar's engagement with the actual ASA setting: this will let you turn it freely until the arrow points toward the original ASA you were comparing with your reference camera (i.e., 100). Tighten the grub screws, and your DP1 meter prism ASA/shutter speed assembly and meter readout should now be in agreement with any other known-good camera you compare it with. Of course if there is a more significant defect in your DP1 like a bad CdS cell or bald patch in ring resistor, you'll still encounter intermittent problems. In that case, have the prism professionally serviced or buy a replacement meter prism.

Note there is unavoidable wiggle room in the F2 meter prism shutter knob/ASA assembly, due to somewhat loose tolerances required by Nikon's early interchangeable prism design. This results in no two F2 cameras having exactly the same reading, or reading exactly and consistently the same as a modern electronic reference camera. The needle (or LED) display will shift up to a 1/3rd stop in either direction just from touching the shutter/ASA knob. Long time F2 users learn to incorporate this loose tolerance in their exposure measurements, it wasn't much of an issue with most films aside from Kodachrome. While disconcerting in operation, it should have a negligible effect with todays common negative films. As long as your F2 reads within a half stop of your reference camera when you wiggle the shutter knob, don't worry about it.

Edited May 26, 2023 by orsetto

[c_watson1]

Maybe Sover Wong is in the house???

[nic_olas]

On 5/27/2023 at 6:20 AM, orsetto said:

Aaarrggghh! Just realized my attempt to help you with the ASA dial adjustment went off the rails: in trying to visualize the steps, I mis-stated what to do somewhere in the middle. Sorry for the error: ignore my earlier post and start again from here.

First, re-assemble everything you had taken apart, try to reposition the black ASA indicator cap to more-or-less its original position (red arrow on 100,  with ASA 6400 upside down on the right, parallel to the camera front edge).

Take reading with your known-good reference camera at ASA 100 (just an example, it can be any ASA you want). Note the settings the good camera suggests, say 1/250th at f/4.

Now, set your F2 ASA, aperture and shutter speed to match your good camera (i.e. 1/250th and f/4 at ASA 100). If your F2 meter disagrees significantly (needle display is not in the center notch), keep the F2 to your eye while lifting up the ASA collar against spring tension, and turn it in either direction until your F2 meter needle centers in the notch. Release the collar, and the mechanics of your F2 prism baseline ASA index are now adjusted to match the ASA of your reference camera.

However the red indicator arrow of your F2 ASA collar will now be pointing at an "incorrect" ASA number. So you must now loosen the collar grub screws to defeat the collar's engagement with the actual ASA setting: this will let you turn it freely until the arrow points toward the original ASA you were comparing with your reference camera (i.e., 100). Tighten the grub screws, and your DP1 meter prism ASA/shutter speed assembly and meter readout should now be in agreement with any other known-good camera you compare it with. Of course if there is a more significant defect in your DP1 like a bad CdS cell or bald patch in ring resistor, you'll still encounter intermittent problems. In that case, have the prism professionally serviced or buy a replacement meter prism.

Note there is unavoidable wiggle room in the F2 meter prism shutter knob/ASA assembly, due to somewhat loose tolerances required by Nikon's early interchangeable prism design. This results in no two F2 cameras having exactly the same reading, or reading exactly and consistently the same as a modern electronic reference camera. The needle (or LED) display will shift up to a 1/3rd stop in either direction just from touching the shutter/ASA knob. Long time F2 users learn to incorporate this loose tolerance in their exposure measurements, it wasn't much of an issue with most films aside from Kodachrome. While disconcerting in operation, it should have a negligible effect with todays common negative films. As long as your F2 reads within a half stop of your reference camera when you wiggle the shutter knob, don't worry about it.

This is thorough! Thank you kindly. 

I will match and adjust accordingly, but to answer your above question - When you refer to "cover", do you mean the little round black cap with the ASA numbers printed on it? If so, that should not have been removed: you should calibrate the ASA setting with it in place. -  Well I did spin this without the cap on. This is what I mean when I ask if there's any way to know what neutral should be to reset that, replace cap and then adjust asa accordingly  I could put the cap on and for ASA red mark @ 100 visually where in reality under the hood the meter is on 1600ASA for example. Hmm!

 

[Niels - NHSN]

On 5/26/2023 at 10:33 PM, c_watson1 said:

Maybe Sover Wong is in the house???

In 2-3 years from now - or whatever his current waiting is?

[orsetto]

6 hours ago, nic_olas said:

 I could put the cap on and for ASA red mark @ 100 visually where in reality under the hood the meter is on 1600ASA for example. Hmm!

Try not to over-think it: thats how I tripped over myself in my earlier reply to you, despite having done this procedure to several of my own F2 meter prisms. Its easier to do than describe. 

if going on the assumption that the base ASA response of your newly-acquired F2 meter prism was misaligned to begin with, and following my corrected post above, the actual "true" ASA is a floating target that you will first align with a reference meter, then second loosen and reposition the ASA cap/collar so its pointer is aimed at the new reference ASA, then third tighten the collar screws to officially lock down the new "home" position.

From then on, any change to the prism ASA setting should track accurately. The priority is to get the prism meter ASA baseline to match your reference meter ASA baseline (the rest is mostly cosmetic). This might be easier if you do the alignment at ASA 100, if you want to try make the cap "home" position match how the camera is shown in Nikon's instruction manual.

Whenever I have performed this baseline ASA correction on my own F2 prisms, I never removed the cap/collar: I simply loosened the grub screws, repositioned the red pointer to the corrected ASA, and re-tightened the screws. So I'm not quite certain how one would position the cap/collar if it had been removed without noting its initial position.

When I loosen my collars, they rotate around the ASA number cap without the cap itself moving. It shouldn't really matter exactly how the ASA numbers display, as long as the red pointer is pointing at the correct ASA number (after you adjust the mechanism beneath to match an accurate reference meter). You should be able to get the whole assembly positioned close to how it is shown in the instruction manual.

Some years back, I standardized on the DP-12 (F2AS) meter prism for all my F2 bodies, so I no longer have a DP1/DP11 available to take picture of the dial home position. If it helps, attached is a photo of my last F2A (DP11), set at ASA 400.

 

Edited June 1, 2023 by orsetto

[orsetto]

Note the shutter on my F2 is set to 1/4 sec in above photo, you would need to set your F2 to the same speed to match that top cap position. Ditto if you try to match with the photo in Nikon instruction manual: note the shutter speed indicated  in their photo, and set your shutter knob to the same prior to tinkering with your ASA dial position..

Edited June 1, 2023 by orsetto

[nic_olas]

4 hours ago, orsetto said:

Try not to over-think it: thats how I tripped over myself in my earlier reply to you, despite having done this procedure to several of my own F2 meter prisms. Its easier to do than describe. 

if going on the assumption that the base ASA response of your newly-acquired F2 meter prism was misaligned to begin with, and following my corrected post above, the actual "true" ASA is a floating target that you will first align with a reference meter, then second loosen and reposition the ASA cap/collar so its pointer is aimed at the new reference ASA, then third tighten the collar screws to officially lock down the new "home" position.

From then on, any change to the prism ASA setting should track accurately. The priority is to get the prism meter ASA baseline to match your reference meter ASA baseline (the rest is mostly cosmetic). This might be easier if you do the alignment at ASA 100, if you want to try make the cap "home" position match how the camera is shown in Nikon's instruction manual.

Whenever I have performed this baseline ASA correction on my own F2 prisms, I never removed the cap/collar: I simply loosened the grub screws, repositioned the red pointer to the corrected ASA, and re-tightened the screws. So I'm not quite certain how one would position the cap/collar if it had been removed without noting its initial position.

When I loosen my collars, they rotate around the ASA number cap without the cap itself moving. It shouldn't really matter exactly how the ASA numbers display, as long as the red pointer is pointing at the correct ASA number (after you adjust the mechanism beneath to match an accurate reference meter). You should be able to get the whole assembly positioned close to how it is shown in the instruction manual.

Some years back, I standardized on the DP-12 (F2AS) meter prism for all my F2 bodies, so I no longer have a DP1/DP11 available to take picture of the dial home position. If it helps, attached is a photo of my last F2A (DP11), set at ASA 400.

 

Again, excellent help, thanks!

I matched the meter to a known working meter - ish. Tracks fairly well in bright light which is great news, needle is also no longer jumpy. In low light though, It falls off and tips to overexposed in most low light + any speeds around 30th and below. Maybe the low light CDS has given up the ghost?

My other F2 Prism I have successfully now cleaned the resistor, adjusted the ASA and works really nicely. Have sent a roll in for developing, following the meter, so we'll see how it went!