Nikon F4: Mission Aperture Lever - two ways to fix the aperture problem

Andreas Thaler · Mar 10, 2024

{Moderator note 12 Jan 25: five threads on the F4/F4S aperture lever repair have been merged into the present thread. You may encounter one or two dead links to 'other' threads. The posts they pointed to, are now all part of this thread, which mostly still follows the journey in a logical and chronological order.}

Now that I have a broken F4 to practice with, I'll see if I can solve the gumming problem in the mirror box by cleaning/lubricating. This should make the aperture lever in the mirror box fully movable again and also completely close the small apertures on the lens.

The aperture lever in the mirror box, which doesn't move all the way down when it gets gummed up. This means that the smallest aperture is not completely closed.

I'm following the tutorial from @F4user, which describes how to remove the mirror box in 22 steps. There is no other way to get to the place. I won't show the steps again here, it's all well described in the tutorial, but I will address possible problems that may arise when disassembling/assembling.

After this mission, I can then decide, based on my own experience, whether I should carry out the repair on my mint F4.

An annoying but not fatal problem

Recent tests on several F4s have shown that usually only the smallest aperture on the lens is affected, which then only closes with a delay or does not close completely. The wider apertures close satisfactorily to perfectly fast.

As the camera checks and adjusts the actual exposure again in automatic modes after the shutter is released, there should be no exposure problems here. If so, then with manual setting.

Since you avoid the smallest aperture when taking photos because of diffraction effects, the problem is just annoying but not fatal.

Nevertheless, a 100 percent functioning camera is of course always the goal.

Stay tuned!

Nikon F4: Recommendations and notes

The Nikon F4 from 1988 is arguably Nikon's most capable SLR for manual and AF lenses. Both types can be used without restrictions. Probably the most valuable F-SLR from Nikon, the F4, which is still an ingenious camera for analogue 35mm photography today. For manual lenses, the AF focusing...

www.photrio.com

Andreas Thaler · Mar 11, 2024

What I also observed is that closing the smallest aperture also depends on the spring tension of the aperture lever on the lens side.

This pull acts on the aperture lever in the mirror box and is strongest when the aperture is open.

When the shutter is triggered, the camera releases the aperture lever in the mirror box and it tilts downwards. In the ideal state, it does this fully; when it becomes resinous, the lens virtually helps against resistance.

Obviously, the spring tension on the Nikkors is different, as is the distance that the aperture lever has to travel to build the smallest aperture. That's why the problem with resin in the mirror case affects some lenses more and some less.

The question remains whether it is worth solving the problem by removing the mirror box, since the impact is manageable in practice.

This mission will find out

chuckroast · Mar 12, 2024

Andreas Thaler said:
What I also observed is that closing the smallest aperture also depends on the spring tension of the aperture lever on the lens side.

This pull acts on the aperture lever in the mirror box and is strongest when the aperture is open.

When the shutter is triggered, the camera releases the aperture lever in the mirror box and it tilts downwards. In the ideal state, it does this fully; when it becomes resinous, the lens virtually helps against resistance.

Obviously, the spring tension on the Nikkors is different, as is the distance that the aperture lever has to travel to build the smallest aperture. That's why the problem with resin in the mirror case affects some lenses more and some less.

The question remains whether it is worth solving the problem by removing the mirror box, since the impact is manageable in practice.

This mission will find out

You may find that dripping the tiniest amount of naptha into the opening behind the lever may free up the gunk.

I've done this with leaf shutter trains, film cocking mechanisms, film counters, etc. and had generally good results.

I've not tried it with this camera, so if others know reasons to not do it, I'd listen to them, but naptha (in TINY amounts tends to dissolve and loosen packed lubricants and significantly improve mechanical action. You'd think this would be temporary, at best, but I've used this any number of times for long term fixes. For example, I had an M645 with a sticky film counter I fixed doing this. That fix lasted for many, many years. When it finally gummed up again, I repeated the process and all was well.

Andreas Thaler · Mar 13, 2024

chuckroast said:
You may find that dripping the tiniest amount of naptha into the opening behind the lever may free up the gunk.

I've done this with leaf shutter trains, film cocking mechanisms, film counters, etc. and had generally good results.

I've not tried it with this camera, so if others know reasons to not do it, I'd listen to them, but naptha (in TINY amounts tends to dissolve and loosen packed lubricants and significantly improve mechanical action. You'd think this would be temporary, at best, but I've used this any number of times for long term fixes. For example, I had an M645 with a sticky film counter I fixed doing this. That fix lasted for many, many years. When it finally gummed up again, I repeated the process and all was well.

I agree

I combined lighter fluid with graphite:

Nikon F4: Quick fix for gummed mechanics parts?

One problem with the Nikon F4 is resin buildup in the mechanics of the mirror box, which prevents the small aperture values from forming. In addition, a scratching noise can be heard when you press the stop down button. The camera has to be heavily dismantled for cleaning and lubrication...

www.photrio.com

Christiaan Phleger · Mar 13, 2024

Hey all, I've been lurking on this and the other thread, and I thought I'd chime in. I did this fix a few years ago on a number of old F4's that were heavily used, at least 3-4 bodies, some minor some more serious of a slow down of the lever. All of the bodies were super well used after thousands of rolls doing weddings and while basically in good nick the slow lever action would make inconsistencies and I had really nothing to lose. I did a number of attempts, with CRC electrical cleaner first with operating the camera while spraying thru a long thin straw to try to target the 'joint' where that lever pivots, if you can see the part on an exploded F4 diagram you'll see what I was aiming at. After a good amount of spray/shutter cycle I switched to a more precise method of tracing the lever down with a thin wire and then dripping small drops of lighter fluid (Naphtha) and then cycling the camera plenty of times, doing this a couple of times finishing with lots of spray air targeted to dry the area. When things felt smoother, less sticky, I followed up with the same method of dripping tiny drops along a wire, but with this last one with CRC greaseless lubricant, not much. My theory was from the first cleaning as a general clean for the area, then the Naphtha as a more targeted clean, and then a tiny amount of lubricant. I think, (its been more than a few years, at least 5-6) I stopped doing the first spray after the first one and just did small amounts of Naphtha to clean, cycle until things seem better, then spray air to clean. I'd let the camera sit for a day or more then check the aperture lever operation with known test lens, if there was any slowness on *the first* cycle then I'd repeat the whole process. If and when a camera would pass that test I'd let it set a week and test. I think most of the bodies needed at least 2-3 attempts, and I would test them with film by putting the camera on A and shooting a sequence while moving the aperture ring from wide open to full stopped down. If there was any and I mean any residual lag the negatives would show over exposure, a correctly working lever would give perfectly even negatives which would be obvious when the negs were put on a light table.

As it was/is, I managed to revive those bodies and I passed one or two bodies off to friends/family and kept two or three, I lost those and several newer F4's (and a whole lot of other stuff) in the Lahaina wildfires, but I did save one F4 with MB-20 that I used to photograph the fire and its aftermath. That F4 was one of those that I did the revive on, and its been a regular shooter for me with no exposure errors, but I do try to shoot a roll a month with it.

Of course YMMV, but this worked for me. I now routinely test any F4 I find for sale by using the stop down lever and feeling how smooth it is and listening to the sound, if its too 'creaky' I figure its slow, and offer accordingly. Good luck with the mission, I will be following along.

Andreas Thaler · Mar 13, 2024

Thanks @Christiaan Phleger!

I have now collected a few F4 here, all of them in mint condition, and almost all of them have the aperture problem.

I was able to improve the F4 that I am currently working with with Zippo/graphite and it produces perfect negatives, see

Thread 'With the Nikon F4s in Vienna'
https://www.photrio.com/forum/threads/with-the-nikon-f4s-in-vienna.205471/

The automatics measure the exposure again immediately before the shutter opens and thus take deviations in the aperture into account, at least that is my assumption with a racehorse like the F4.

Today I would like to see how challenging it is to remove the mirror box so that I can examine the affected area.

Pragmatically speaking, it's not worth putting a nice F4 at such risk since it works. It starts with the button covers, which can probably only be removed if they are damaged.

I know more tonight!

Andreas Thaler · Mar 13, 2024

Disassembly, removal of the mirror box

In order to get to the point where the problem with the gummed mechanics is located, the mirror box must be removed. On the F4 this is the front part of the camera.

I followed the tutorial from @F4user, which shows all the necessary steps:

Nikon F4 aperture lever repair

WARNING : Those instructions are for skilled persons with some knowledge of mechanics and electronics. Don't follow if you are unsure about your skills. F4 Aperture lever problem driving the lens down. This will be a long thread with ~100...

www.photrio.com

I'm just showing a few impressions or giving hints here.

My training F4 with defective shutter priority and program modes. The electronics are probably faulty here. No chance of repairing it, most of the circuitry is in ICs across the camera.

It already served as a donor for the LCD built into the camera, which I used to replace the one on another F4 („bleeding“):

Thread 'Nikon F4: Upper LCD replaced'
https://www.photrio.com/forum/threads/nikon-f4-upper-lcd-replaced.205147/

No particular difficulties here, all screws can be loosened easily.

With the circlip I was careful not to bend it. It can be levered out or pushed away using one or two screwdrivers with a small flat blade. You have to try out what works better.

The cover cap for the screw on the exposure compensation ring is made of soft plastic, and the ring is also plastic. It can be levered out and is glued to the screw. Using a screwdriver with a small flat blade will help you get ahead without causing too much damage to the cap.

Someone had already worked on the camera here, the mark on the cap was not caused by me.

The rubber cover on the rotary knob for the shutter times can be lifted off, be careful, it can tear.

Be careful when using the screwdriver as a lever, the plastic cover underneath scratches easily.

The knob is also made of plastic.

Plastic here too.

chuckroast · Mar 13, 2024

Andreas Thaler said:
I agree

I combined lighter fluid with graphite:

Nikon F4: Quick fix for gummed mechanics parts?

One problem with the Nikon F4 is resin buildup in the mechanics of the mirror box, which prevents the small aperture values from forming. In addition, a scratching noise can be heard when you press the stop down button. The camera has to be heavily dismantled for cleaning and lubrication...

www.photrio.com

The problem with graphite is that it can get in the way of other mechanical motion and possibly even interfere with impedance in circuitry. I prefer straight naptha as it disolves build up, but then dries off with little or no residue.

Andreas Thaler · Mar 13, 2024

To get to this screw, the red rubber marking dot must be levered out. It's also glued on.

I don't want to use isopropyl alcohol as a solvent here because the cover is made of plastic.

The base plate is screwed on and also glued to the plate for the tripod screw.

To hold the camera in place, I use my circuit board holder, which is actually intended for soldering work.

The tools from iFixit prove themselves here again when removing the two rubber shells that are glued to the case.

Desoldering cables is quick, clean and easy if you first apply flux to the soldering points.

Done!

After loosening a few screws and disconnecting the ribbon cables, the front part with the mirror box (above) can be removed.

The problem area and search for a solution without having to dismantle the F4

And here, on the right side of the mirror box, is the problem area in the aperture mechanics that inhibits the aperture lever in the mirror box.

@F4user instructs that a gear and a cover must be removed to clean the area.

The arrow points to the place where the gear, secured with a circlip, sat. The cover has already been removed underneath.

A spring runs off and moves the remaining gears when removing the gear mentioned. It was then no longer clear to me how to get tension on the spring again.

The darker gear in the middle cycles rapidly when the mirror is triggered or the aperture lever in the mirror box is moved.

On this F4, the aperture lever worked, but the mechanics were already a bit sluggish and the gear only turned slowly. I couldn't see any gumming or traces of lubrication and drizzled the area with benzine. Then everything ran quickly and easily.

I will observe whether the mechanics continue to run smoothly after this treatment.

If yes, then the problem can be solved with benzine only. And if you can get the benzine to the spot without dismantling the camera, it would be easy and risk-free.

Because the effort required to remove the mirror box is considerable. And then everything has to be reassembled again without errors or damage.

In addition, the electronics are exposed and are generally susceptible to electrostatic discharges.

All good reasons not to disassemble the camera.

Here you can see all disassembled parts. These are not a few:

There is an IC on the circuit board underneath. It should be insensitive to benzine, which evaporates quickly:

When the mirror box is installed, the aperture mechanism is directly opposite the shutter mechanism. Again, I don't see any parts that could be sensitive to benzine here:

Andreas Thaler · Mar 13, 2024

Troubleshooting without disassembly of the F4?

My first attempt to solve the problem on another F4 with the aperture lever being stiff was to apply a mixture of Zippo and graphite behind the lever with a pipette. I only knew roughly where the problem was.

But now I see the area and can think about how I can insert benzine (Zippo should work too) precisely.

This can be done with the cannula of a syringe:

However, I can't get to the spot with a straight cannula when the mirror box is installed. So I have to bend the cannula to fit:

Using the Dremel and a corundum grinding stone, I grind the sharp tip of the cannula round to avoid damaging the camera when using it:

This allows me to reach the spot in the mirror box:

Here is a view of the removed mechanics. The tip of the cannula reaches exactly the spot:

The cannula must be inserted at an angle from above, with the camera standing upright. Then the benzine is distributed over the area from top to bottom:

That should work.

I just need to practically test it on an F4 with the aperture problem. Provided that the removed aperture mechanism, which has already been treated with benzine, continues to run freely.

Now I'll let the project rest and think about everything again.

Conclusion

Removing the mirror box is labor-intensive, but does not present any particular challenges.
It is important to document the removed parts precisely so that the assembly works.
Soldering skills must be present, the soldering points are all easily accessible.
All screws could be removed without any problems, even those that were secured with adhesive. This could also be because the camera has already been opened once.
You should work with a grounded work mat to avoid damage to the electronics caused by electrostatic discharges.
Disassembling the aperture mechanism brought up a problem with a spring that I couldn't solve. So this method is out of the question for me.
The process of putting a camera back together properly is always longer and more strenuous than dismantling it.
I assume that the aperture problem can be solved with benzine (Zippo) alone, and without lubrication.
If this is achieved by introducing the benzine with a syringe, the camera does not have to be disassembled.
A practical test should show whether the method works.

Some more impressions of the complex inner workings of the F4

+++

All information provided without guarantee and use at your own risk.

Chan Tran · Mar 13, 2024

When you removed the rewind crank did you see the clutch in the rewind crank? I think mine is slipping so although I hear the motor run it doesn't rewind with power.

Andreas Thaler · Mar 13, 2024

Christiaan Phleger said:
Hey all, I've been lurking on this and the other thread, and I thought I'd chime in. I did this fix a few years ago on a number of old F4's that were heavily used, at least 3-4 bodies, some minor some more serious of a slow down of the lever. All of the bodies were super well used after thousands of rolls doing weddings and while basically in good nick the slow lever action would make inconsistencies and I had really nothing to lose. I did a number of attempts, with CRC electrical cleaner first with operating the camera while spraying thru a long thin straw to try to target the 'joint' where that lever pivots, if you can see the part on an exploded F4 diagram you'll see what I was aiming at. After a good amount of spray/shutter cycle I switched to a more precise method of tracing the lever down with a thin wire and then dripping small drops of lighter fluid (Naphtha) and then cycling the camera plenty of times, doing this a couple of times finishing with lots of spray air targeted to dry the area. When things felt smoother, less sticky, I followed up with the same method of dripping tiny drops along a wire, but with this last one with CRC greaseless lubricant, not much. My theory was from the first cleaning as a general clean for the area, then the Naphtha as a more targeted clean, and then a tiny amount of lubricant. I think, (its been more than a few years, at least 5-6) I stopped doing the first spray after the first one and just did small amounts of Naphtha to clean, cycle until things seem better, then spray air to clean. I'd let the camera sit for a day or more then check the aperture lever operation with known test lens, if there was any slowness on *the first* cycle then I'd repeat the whole process. If and when a camera would pass that test I'd let it set a week and test. I think most of the bodies needed at least 2-3 attempts, and I would test them with film by putting the camera on A and shooting a sequence while moving the aperture ring from wide open to full stopped down. If there was any and I mean any residual lag the negatives would show over exposure, a correctly working lever would give perfectly even negatives which would be obvious when the negs were put on a light table.

As it was/is, I managed to revive those bodies and I passed one or two bodies off to friends/family and kept two or three, I lost those and several newer F4's (and a whole lot of other stuff) in the Lahaina wildfires, but I did save one F4 with MB-20 that I used to photograph the fire and its aftermath. That F4 was one of those that I did the revive on, and its been a regular shooter for me with no exposure errors, but I do try to shoot a roll a month with it.

Of course YMMV, but this worked for me. I now routinely test any F4 I find for sale by using the stop down lever and feeling how smooth it is and listening to the sound, if its too 'creaky' I figure its slow, and offer accordingly. Good luck with the mission, I will be following along.

I see your method confirmed by my experiment

Andreas Thaler · Mar 13, 2024

We also sometimes cook in our kitchen

Andreas Thaler · Mar 13, 2024

Chan Tran said:
When you removed the rewind crank did you see the clutch in the rewind crank? I think mine is slipping so although I hear the motor run it doesn't rewind with power.

No, unfortunately not.

But the rewind crank slipped into the film cartridge chamber. Now I can't get the back door open anymore. I should have left it open.

Andreas Thaler · Mar 13, 2024

And that was the first and successful use of my new screw extractor

Post in thread 'Tools on iFixit'
https://www.photrio.com/forum/threads/tools-on-ifixit.205179/post-2776288

I had overtightened the screw head profile and was able to remove the screw.

It is important to place the screw extractor vertically and press it firmly. Otherwise the tool will mill out the screw head.

Andreas Thaler · Mar 13, 2024

chuckroast said:
The problem with graphite is that it can get in the way of other mechanical motion and possibly even interfere with impedance in circuitry. I prefer straight naptha as it disolves build up, but then dries off with little or no residue.

Yes, I was aware of that and that's why I hesitated for a long time before trying it on my F4. Directly under the spot is a circuit board with an IC. But it went well.

Andreas Thaler · Mar 13, 2024

Unfortunately, the screw extractor was unsuccessful with another F4 screw.

So I milled out the screw head with the tungsten carbide cutter on the Dremel.

I couldn't unscrew the remaining screw part with the thread with the combination pliers.

But another tool did that effortlessly, the PZ-57 Mini Screw Removal Pliers:

Post in thread 'Tools on iFixit'
https://www.photrio.com/forum/threads/tools-on-ifixit.205179/post-2774403

Now my second F4 has a replacement rewind crank with screw.

Thanks to the training F4!

Andreas Thaler · Mar 13, 2024

Andreas Thaler said:
No, unfortunately not.

But the rewind crank slipped into the film cartridge chamber. Now I can't get the back door open anymore. I should have left it open.

The back door can be unlocked using this lever, even if the rewind fork has fallen into the film cartridge chamber:

Christiaan Phleger · Mar 13, 2024

WOW! An excellent guide!
Your solution with the angled pipe for the benzine is essentially what I was attempting to do, and I came to the same conclusion as you did from looking at exploded diagrams and a lot of cycling the camera. I wanted to not break the mirror box seal, I had an F4 I sent to Nikon NPS and it was returned with the focus slightly off which I did not test and catch until the processed film was ever so slightly off, I don't have the precision to accurately set the mirror box back to correct spec, perhaps when you reassemble one you can test this.

Also, it was the F5 that had the shutter monitor that would correct the movement of the 2nd curtain stack to (potentially) correct erroneous shutter speeds, not the F4.

As well, I did consider mixing the benzine with graphite like you did but settled on just a tiny amount of a silicone/greaseless lubricant since I believe the original parts had either none or very little lubrication, as evidenced by your dismantling of the area shows that there is no large build up of old grease/lubricant. In my own fixes I felt that just a 'clean' repair left the mechanism feeling a touch dry. Perhaps I'll see if I can find the factory repair manual and trace down the lubricants used and where on the F4.

Well done!

chuckroast · Mar 13, 2024

Christiaan Phleger said:
As well, I did consider mixing the benzine with graphite like you did but settled on just a tiny amount of a silicone/greaseless lubricant since I believe the original parts had either none or very little lubrication, as evidenced by your dismantling of the area shows that there is no large build up of old grease/lubricant.

Have done a fair bit of DIY camera repair over the past decade, it has been my consistent experience that it is rarely a lack of lubrication that causes problems like binding. It most usually is just accretion of dirt. Flushing the offending surfaces with naptha in small, controlled amounts has helped me fix all manner of camera grumpiness.

Even when surfaces were lubricated, that lubricant packs with time and literally gums up the works. I have and original Nikkormat Ft here with a working meter that I like as a knock about body. The film advance lever was not returning to starting position. I took the bottom off the camera and saw that the original grease was hardened and packed. I cleaned the track that mechanism rides on and got rid of all that packed gunk. Then I applied the tiniest amount of white silicone grease to the moving surfaces and it was like new.

Andreas Thaler · Mar 13, 2024

Christiaan Phleger said:
WOW! An excellent guide!
Your solution with the angled pipe for the benzine is essentially what I was attempting to do, and I came to the same conclusion as you did from looking at exploded diagrams and a lot of cycling the camera. I wanted to not break the mirror box seal, I had an F4 I sent to Nikon NPS and it was returned with the focus slightly off which I did not test and catch until the processed film was ever so slightly off, I don't have the precision to accurately set the mirror box back to correct spec, perhaps when you reassemble one you can test this.

Also, it was the F5 that had the shutter monitor that would correct the movement of the 2nd curtain stack to (potentially) correct erroneous shutter speeds, not the F4.

As well, I did consider mixing the benzine with graphite like you did but settled on just a tiny amount of a silicone/greaseless lubricant since I believe the original parts had either none or very little lubrication, as evidenced by your dismantling of the area shows that there is no large build up of old grease/lubricant. In my own fixes I felt that just a 'clean' repair left the mechanism feeling a touch dry. Perhaps I'll see if I can find the factory repair manual and trace down the lubricants used and where on the F4.

Well done!

Thank you very much! I think we are on the right track

I would also have concerns about adjusting the mirror box when assembling.

Actually it should be enough to simply screw it back on, but this is about micrometers and it probably won't be that easy.

Now I just have to get over myself and try the method on an F4 with an aperture problem

Andreas Thaler · Mar 13, 2024

chuckroast said:
Have done a fair bit of DIY camera repair over the past decade, it has been my consistent experience that it is rarely a lack of lubrication that causes problems like binding. It most usually is just accretion of dirt. Flushing the offending surfaces with naptha in small, controlled amounts has helped me fix all manner of camera grumpiness.

Even when surfaces were lubricated, that lubricant packs with time and literally gums up the works. I have and original Nikkormat Ft here with a working meter that I like as a knock about body. The film advance lever was not returning to starting position. I took the bottom off the camera and saw that the original grease was hardened and packed. I cleaned the track that mechanism rides on and got rid of all that packed gunk. Then I applied the tiniest amount of white silicone grease to the moving surfaces and it was like new.

Excellent - we agree, the benzine lobby!

Andreas Thaler · Mar 13, 2024

I'm surprised at how many parts on the F4 are made of plastic. And yet it's so solid, or maybe that's why.

The Nikon F3 as its predecessor is a different class of construction with metal throughout.

The F4 from 1988 can certainly be compared with the Minolta X-700 from 1981. A die-cast chassis, many plastic parts and integrated electronics.

chuckroast · Mar 13, 2024

Andreas Thaler said:
I'm surprised at how many parts on the F4 are made of plastic. And yet it's so solid, or maybe that's why.

The Nikon F3 as its predecessor is a different class of construction with metal throughout.

The F4 from 1988 can certainly be compared with the Minolta X-700 from 1981. A die-cast chassis, many plastic parts and integrated electronics.

I have owned - and heavily used - the Nikkormat Ft and all the F body variants up to- and including the F3. I currently own 5 such bodies, all in good working order. I like them all for different reasons, but to my mind, the best film body Nikon ever built was the F2 Photomic. It's the natural heir to the Nikon F Photomic FtN and improves upon it in very subtle but good ways. I love my F3 but the fact that it needs a battery to be operated and has that ridiculous illuminator business on the finder makes it inferior to the F2, even though the F3 shutter is pretty much bulletproof.

I quit looking after the F3 because I never wanted auto-anything. Then I got a D750, which is a quite capable machine, but it confirmed my hatred of cameras that take over the work

Andreas Thaler · Mar 14, 2024

I think the Nikon F4 is a brilliant illusion in terms of the materials used. I suspected plastic fittings without really realizing it

But in many ways plastic is a better material than metal for camera bodies.

In any case, it is just as heavy a tank as the contemporary Canon T90, which is similarly made.

Nikon F4: Mission Aperture Lever - two ways to fix the aperture problem

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