50mm f1.4 FL Won't Stop Down

[leigh_marrin]

<p>I recently bought a Canon Pellix that has a 50mm f1.4 FL lens, an early version of the f1.4 lens with a serial number in the 48,000 range. On the Pellix body this lens would not stop down, in either the A or M mode. I replaced it with a 50mm f1.8 FL, which works perfectly.</p>

<p>Looking at the 50mm f1.4, the glass and body are in good shape--no external visible problems. Comparing the rear pin that actuates the iris on my f1.8 and f1.4, both have the same amount of spring tension. But the f1.4 won't stop down...</p>

<p>I suppose it's unlikely, but I'm hoping there is an easy fix for this problem; any suggestions? Assuming it requires a repair tech to fully disassemble it to fix the frozen aperture, is the early version of the 50mm f1.4 really worth fixing?</p>

<p>Thanks for any info and suggestions. --Leigh.</p>

[User_502260]

<p>Assuming that the aperture blades have not been removed for some special purpose then the lubricant may have just dried up or become too thick for things to move. The early 50/1.4 FL is by most accounts a decent performer. I have one which also won't close down and which is on a FP body. This version of tghe 50/1.4 went out of production in 1968 when the FL II came out. The FL II is a seven element design and is very good. When I have time I will get the stuck lens serviced. It's the right lens for the FP. Any of the 50/1.4 FD lenses should work on your Pellix or Pellix QL and these are also avalable at very reasonable prices now.</p>

<p> </p>

[gordon_yee]

<p>I agree with Jeff, the diaphragm blades on your lens probably got contaminated by oil that seeped in from the focusing helicoid's grease. This is a fairly common problem with lenses of this vintage. The earlier, six element version of the FL 50mm f/1.4 lens is a very good performer as is its close contemporary cousin, the S-mount 50mm f/1.4 lens for Canon rangefinders. However, unlike the RF lens, the market value of the FL version is probably less than the cost to have it serviced by a professional repairman.</p>

<p>Of course, you can still use the lens at maximum aperture if you don't get it repaired. If you are mechanically inclined and willing to assume the risk, it's pretty easy to gain access to the diaphragm blades through the front of the lens. With patience and careful, repeated application of a Q-tip soaked with a solvent such as naptha, the blades can be freed up and cleaned without removing the diaphragm. There are two steps to disassembly:</p>

 

<ol>

<li>The ID ring at the front of the lens threads in by way of the filter threads. You'll need to use a friction tool of some kind to unscrew it. Be careful not to damage the front lens element.</li>

<li>The three elements at the front of the lens can be removed as a single unit using a spanner wrench of about 52mm in diameter. After its removal, you'll have direct access to the diaphragm as well as the front of the fourth lens element.</li>

</ol>

<p>Good luck with whatever action you decide to take.</p>

[leigh_marrin]

Jeff and Gordon, thanks very much for the quick replies. I'm a little timid about opening up the lens--don't have a lens

spanner, so may just try to find another 50mm f1.4.

 

 

Another question--my 50mm f1.4 FL lens has quite a yellowish cast to it, unlike my other FD and FL lenses. Is this normal?

[gordon_yee]

<p>If you decide to purchase another 50mm f/1.4 lens, I'd suggest that you get one of the seven element designs. The image quality of the six element version you currently have will only be marginally different or, more likely, indistinguishable from your FL 50mm f/1.8. On the newer seven element FL 50mm f/1.4, the A/M diaphragm ring is located at the back of the lens next to the breech lock ring. On the older lens, the A/M ring is at the front just behind the chrome aperture ring. Alternatively, all of the FD and the New FD 50mm f/1.4 lenses are seven element designs and are fully compatible with all Canon FL mount bodies, including your Pellix.</p>

<p>Is the yellowish cast visible when you look <em>through</em> the lens at a white surface, or are you referring to the color of light that reflects off of the lens coating when viewing the front surface of the lens at an angle? The former indicates a change in the Canadian balsam used to glue lens elements together as a result of aging or the presence of radioactive glass. While there is evidence that the Canon FL 50mm f/1.8 lens contains thoriated (e.g., radioactive) glass, I don't think this is the case with the f/1.4 lens. Does your f/1.8 lens also have a yellow cast? I just checked one of my six element FL 50mm f/1.4 lenses (s/n 433xx) and it does not have a yellow cast. My recollection is that most of my FL 50mm f/1.8 lenses have the telltale yellow cast indicating the presence of thoriated glass.</p>

[magnus_aren]

<p>I am having the same issue,<strong> I think</strong>. I just recently bought an older FL 50mm 1.4 and the aperture blades seems stuck wide open. I am not sure though, since I am not able to mount it on a camera right now.<br>

My question is, will I need to mount it on a camera to test the aperture blades, or should the blades be able to stop down in the manual setting without being mounted? Or in the auto setting by triggering the little lever in the mount?<br>

I've read that this lens doesn't stop down until the shutter is fired, so there might not be a problem with it?<br>

I don't really mind opening it up to clean the blades, because I love trying to fix things. But it would be a bit of a waste to try to fix something that isn't broken.<br>

Thankful for any help on this.</p>

[gordon_yee]

<p>There are two ways to test the diaphragm on an unmounted FL lens. Set the chrome aperture ring to a smaller f/stop, such as f/16, and then (a) move the spring loaded aperture lever/rod on the back of the lens counterclockwise, or (b) move the A/M ring to the "M" setting. In either case, the diaphragm should close to the selected f/stop if it's working properly. If it doesn't close, the leaves of the diaphragm are probably stuck due to dried lubricant that migrated from the focusing threads.</p>

[gordon_yee]

<p>Here's a shot of my FL 50mm f/1.4 six element lens with the ID ring and front lens block removed, allowing direct access to the diaphragm. The friction device can be as simple as a wide sticky rubberband and two fingers or a rubber sink stopper. The outer edge of the front lens assembly has two slots for the jaws of a spanner wrench or an improvised equivalent. The blades of the diaphragm were clean and dry on this lens. However, the lens elements had some fogging and a mild case of fungus which needed attention.</p>

<p><a href="/bboard/photo?photo_id=17743676&size=lg"><img src="http://d6d2h4gfvy8t8.cloudfront.net/17743676-md.jpg" alt="Canon FL50 f/1.4 - Cleaning Diaphragm" width="401" height="470" border="0" /></a></p>

[leigh_marrin]

Gordon, I got the lens apart! Well, I removed the front ring and front lens cell thanks to your excellent instructions and photo. For a lens

spanner I used the ID-measuring prongs on a junky vernier calipers--worked great, and no damage to the calipers.

 

 

I can now see the edges of the iris leaves, but what next? Were I to flood them with naptha, I'll probably stain the rear cell--is it as easy to

remove and clean?

 

 

Anyhow, thanks again. FWIW, the front cell of my 50mm f1.4 looks like it will cover most of a 4x5 image area; may tape it to the front of my

Speed Graphic, and see what results.

[gordon_yee]

<p>Congratulations, Leigh! It's nearly impossible to keep the lens surface just beyond the diaphragm clean. On the FL lenses I've serviced, cleaning this lens surface is the last thing I do before reassembling the lens. While you can do a more thorough job of cleaning the diaphragm if you remove it, I prefer to clean it while still in the lens barrel due to the added complexity involved. This makes the cleaning process more time consuming, especially if both sides of the diaphragm are saturated with dried lubricant. On FL lenses that I've cleaned, it's relatively easy to remove both the front and rear lens blocks without disassembling the focusing helicoid to gain access to both sides of the diaphragm. However, since this is your first repair job, I'd strongly recommend that you keep it simple and just clean the diaphragm from the front. If the contamination isn't too bad, you may be able to get the diaphragm working without the need to do any more disassembly. Even though the FL lens mount is much simpler than an FD mount, it's easy to mess up if you have no experience in its disasembly and reassembly.</p>

<p>Everyone has their own methods and techniques. Here's how I clean an FL lens diaphragm from only the front of the lens:</p>

 

<ul>

<li>First of all, I never flood the diaphragm with solvent to the point where excess fluid could flow anywhere else in the lens. I would first run a Qtip soaked with naptha along the outer rim of the diaphragm. Pay particular attention to the eight equally spaced pins on the rim which are the pivots for the diaphragm blades. After the naptha has had time to soak in, it may free up the blades sufficiently for the diaphragm to close. Test it by setting the A/M ring to "M" and turning the aperture ring.</li>

<li>Once you get the diaphragm to close, you'll probably see a film of oil on the blades. Close the diaphragm to the smallest aperture and, using your solvent-soaked Qtip, clean the entire surface. With the blades still wet, I repeatedly open and close the diaphragm to work the solvent into the recesses of the mechanism as well as on the back surfaces of the blades. You main notice a brown stain on the Qtip which will be the lubricant removed from the blades.</li>

<li>By repeating the process of cleaning the blades and then working the diaphragm mechanism, you continue to remove some of the old lubricant and dissolve more of it with the new solvent. The brown staining should become less apparent as you clean. You can check the progess on the back of the diaphragm by looking at it through the back of the lens.</li>

<li>When the blades are sufficiently clean and the diaphragm operates properly, let any remaining solvent evaporate before cleaning the lens behind the diaphragm and reassembling the lens. The process can be accelerated with the careful application of compressed air.</li>

</ul>

<p>Over time, the diaphragm may become sluggish due to additional lubricant migrating to the blades. However, opening the lens and cleaning it a second time should be a lot easier.</p>