aperture blades out of alignment?

Discussion in 'Nikon' started by pennet_smith, Nov 29, 2013.

  1. Hello all, (sorry in advance, my images in question are just linked. They're high resolution so you can see in detail the problem I am talking about. It didn't make sense to downsize them so the forum could display them as you'll need to see the full resolution ones anyway, so I just linked those)
    I got a new lens recently, a 28mm NIkon/Nikkor f/1.4D, and it's been great, but a friend of mine picked up on something that might be a fault with it. I am interested in input from both people knowledgeable with aperture blades as well as this lens specifically. My friend seemed to think that it was odd, but probably just how the lens is built and I would like to compare it with one of its siblings.
    First off, he noticed that something was off with the aperture blades
    Click for full sized image #1
    and we saw it in the bokeh
    Click for full sized image #2
    at f/1.4 it's not so bad
    Click for full sized image #3
    Click for full sized image #4
    but it starts to get bad near f/1.8 (I would even say f/1.6) and is really bad at f/2.0, after f/3.5 it's totally fine.
    Click for full sized image #5
    You can see in the top left, that you're not just seeing the steps/layers of the aperture blades. It seems like one side isn't closing correctly >_< I have a 50mm f/1.4 D as well and that has no problems whatsoever
    Click for full sized image #6 (I wrote on the photo that it's an 8 blade lens, that's wrong; it's a 7 blade)
    Never do you notice a step when looking at the blades, and the Bokeh is always really round.
    Now I know that the 50mm only has 7 blades, but I heard that 9 blades like what is in the 28mm was meant to produce a more round bokeh.
    Does anyone think this is a problem with the aperture blades themselves or can anyone with this same lens confirm that this is just infact how this lens is constructed and it is meant to be like this? When looking at other 9 blade lenses like the 50mm f/1.2 it does look like it has a bit of jag/the blades don't produce a totally round hole, but the movement/opening doesn't seem to as off as mine where the blades seem to be at different points on their track.
    [​IMG]image #7
    The bottom only looks slightly more closed than the top but you can still see a difference as the top looks more open than the bottom. Is this just a thing 9 bladed lenses do as a consequence of having so many blades laying on top of each other and competing for room? It'de be cool to see photos of your aperture blades (of the same 28mm f/1.4 D lens) and your bokeh photos to compare. I live in Canada and I'm debating sending it to one of the Nikon repair centres to have it fixed if it is really a defect. I'm going to try contact them in the morning too when they're open.
    (Also when you reply, I'de appreciate it if you use the image #s so that it's clear which examples we're referring to.
     
  2. Pennet, I sold my 28mm f/1.4 AF-D for way, way more than I paid for it in the process of buying the newish 24mm and
    35mm f/1.4G lenses. I do not recall there being any deformation in the aperture blade pattern on my 28mm f/1.4.

    At f/1.4, you would not see any deformation as the blades should be fully retracted. The bokeh, with a point light source
    should be a circle, with the center of the circle being a little darker, due to the f/1.4 AF-D lens being aspheric.

    If you're in the U.S., I would consult with Nikon's service department in Melville, NY, to see if your lens' aperture is within
    factory specifications. Note that if your lens was originally purchased gray market in the U.S., Nikon U.S. may refuse to
    work on the lens.

    One other bit of advice if you keep the lens, the AF/MF ring is thin and flimsy. Mine broke twice, and I'm very gentle with
    my equipment. As the lens is discontinued and Nikon isn't making more parts for the lens, contact Nikon's parts
    department in El Segundo, CA, and see if they can order you an AF/MF ring or two from Japan.
     
  3. It does seem strange that the f/1.4 shots don't show completely round OOF highlights Pennet. It also looks as if the aperture is off-centre WRT the lens assembly, but this may be because it was photographed at an angle.
    Could I suggest you submit another series of shots of the lens and aperture blades? This time making sure that the lens is placed flat down on a surface and that the taking lens is absolutely centred on it. Otherwise we can't tell if the iris assembly is misplaced axially, or if we're just looking at it on the skew. Some extra distance between the subject and camera would help a lot here.
    It's not unusual to have blades that don't overlap perfectly all the way round, and it's not peculiar to irises with a large number of blades. In fact it's less usual to see in an iris with a greater number of blades. Incidentally the blades don't 'stack' more than two deep until the aperture is well closed down. The issue with your lens appears to be at more open apertures. Also the word 'elements' refers to the number of glass components making up a lens, not to the number of aperture blades.
     
  4. I thought the lighting on the above 50mm f/1.2 picture looked familiar. From the serial number of the lens, it's easy to track the origins of that picture to Ken Rockwell's website. Pennet, simply blanking out the copyright logo doesn't give you the right to post that picture here!
    The last thing we want is to give Ken the satisfaction of sueing this site for unauthorised use of one of his pictures, so I'd strongly suggest it's taken down ASAP by a moderator.
     
  5. I am sorry I used one of his photos, but I could not find anything else that displayed a similar issue. I've now found a different example and will update that post.
    Also, I've taken photos of my iris blades, and yes I put my camera on a tripod for this and shot straight down at the lens.
    ---edit---
    okay, I don't seem to be able to edit my first post and remove the Ken Rockwell photo this was what I was going to include in place of it. In this video you can see blades working right @0:15, and they seem to have the same step, but they don't seem to be off centre like mine are where one side is closing faster than the other/at a different point in it's opening.
     
  6. I found some shots someone else took of the same lens online. My guess is the first one is at f/1.4[​IMG]
    and the second one is at f/2.0 (or the first one is at f/1.8 or f/2.0 and the second one is somewhere around f/2.8)
    [​IMG]
    I know this setup is probably too inaccurate to test but here are some similar shots I took of mine.
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    & fully open
    http://i.imgur.com/69NOEujl.jpg
    & at f/4.0
    [​IMG]
    The problem is not that noticeable at f/1.4 but still present, it shows the most between f/1.6, f/1.8, f/2.0, f2.2, f/2.5 and f/2.8; still a little bit at f/3.2 and minor to not at all at f/3.5 and onwards.
    Mostly I'de just really like to find someone with the same lens that I can compare with to see if this is a defect or if the lens is meant to be this way. It makes me wonder as on mine there is a huge step between the blades on the top compared to on the bottom. I also tried phoning Nikon repair but they're not open until Monday. I have a feeling they won't repair this one if it is defective or won't know about it anymore as it's a discontinued lens.
     
  7. ShunCheung

    ShunCheung Administrator

    Pennet, are you showing someone else's images of another sample of the 28mm/f1.8 AF-D, which may potentially be in a very different condition from yours? And are you also showing images of your lens as well? It is getting confusing as it is not entire clearly which image is your lens.
    Could you try to capture some new images showing the current condition of the aperture diaphgram of your lens? Even old images of that same lens might not demonstrate its current condition. Show something around f2.8 and f4 should clarify a lot of issues.
     
  8. The first two photos someone sent me showing their lens, but they only have shown me the back. So I took similar photos of the back of my lens.
    [​IMG]
    This one is his
    [​IMG]
    This one is mine.
    I put arrows in front of, going clockwise, the "steps" that I am talking about. Both of us have bigger steps between the blades near the top and smaller steps near the bottom between blades.
    I'm still trying to find someone who can provide a shot of the front of their lens like this to compare between the two. To me, especially in the second and third frame, it seems like one side of the aperture is opening at a different rate to the other side of the aperture.
     
  9. Why don't you contact Nikon technical support?
     
  10. 9AM-8PM EST, Monday to Friday, same as their repair centres who also may know. I am going to as soon as they open up on Monday.
     
  11. Does anyone think this is a problem with the aperture blades themselves or can anyone with this same lens confirm that this is just infact how this lens is constructed and it is meant to be like this?
    I think it`s a common problem in some lenses. I have seen this in several current Leicas, and I have experienced this issue with two lenses (as far as I recall); one was an Apo- Summicron M 90 asph, the other a Mamiya 50/4. Looks like the aperture blades get "stuck" (or maybe too loose, I don`t know), at the maximum aperture they get sometimes fully open, sometimes not opened at all, with the very same shape you show in the photos of the post above.
    The shape of the aperture, when wide open, should be perfectly circular and with no trace of the aperture blades. When you start to close the diaphragm, the blades start to be noticeable.
    To my understanding, it doesn`t matter at all the shape of the blades once you are turning the ring to close the diaphragm, but if the blades are not correctly placed, the shape could be somewhat odd, like in yours.
    In my own case, I sent the lens to fix the problem. As far as I know, it was an easy fix, no parts needed, not specially expensive, and the lenses came out perfect (I sent them to a free lance, cheaper service). I have used the 50 on the Mamiya quite often since then, and the blades remain in perfect condition.
    Don`t know about Nikon, I`ve never been aware of this issue in one of my lenses yet.
     
  12. Pennet, I don't think you'll get much joy out of Nikon come Monday.
    I've just looked at my 50mm f/1.2 Ai-S Nikkor, and it's actually a bit worse than KR's example. It's very 'spikey' on one side between f/1.4 and f/2.
    The issue appears to be that Nikon have either miscalculated the length of iris blade needed, or deliberately skimped on it. Either way there just isn't sufficient overlap between blades to reliably create a smooth transition. AFAIK this only affects the 9 bladed irises, and none of the 7 bladed lenses suffer in the same way. Although the 7 bladed apertures are still far from round, at least they're not spiked.
    That's just poor design on Nikon's behalf IMO, and they should take a leaf (pun) out of Tamron's book. My Tamron SP 28-75mm zoom and Tamron SP 90mm macro lenses both have superbly rounded apertures that only begin to show their 7 sided nature at around f/8. At wider apertures you have to look quite hard to see any lack of roundness in them.
     
  13. ShunCheung

    ShunCheung Administrator

    Without having Pennet's lens in my own hands, I am not going to comment on whether it is "defective" or not.
    Back in the late 1990's, I had two lenses with stuck aperture diaphragams, and Nikon USA charged about $200 to replaced each one. Essentially that is your worst case scenario.
     
  14. In years past, I have owned a few lenses that exhibited similar odd diaphragm shapes. And I have never worried about it. In my opinion, as long as the diaphragm opens and closes quickly and without random variation in the size of the aperture when closed - don't give it another thought. Just take some pictures. One advantage for Canon Eos users - because of the electronic aperture control, they don't even see stuff like this. :)
     
  15. I've spoken to some other 28mm f/1.4 D owners recently and they've all said that their lens looks the same. Still haven't been able to get a photo to compare though.
    I did find this post though.[​IMG]
    Where someone was asking if his lens on the left was normal, and people said yah it was designed like that. So it looks like some lenses are designed like this.
    I think it`s a common problem in some lenses​
    I'm mostly wondering if the 28mm f/1.4 was designed like this (not if it's a problem) or if just mine is a defect. That's why I originally posted a photo of the 50mm f/1.2 as it was the only other lens I could find with a similar diaphragm.
     
  16. In my opinion:
    Wide open, the lens should show a perfectly circular aperture, and a perfectly smooth shape in out of focus light spots. If not, the lens should be serviced. I`ve had two lenses showing this problem, and after a visit to the repairman, the problem was fixed. As mentioned, it was an easy fix, no need of replacement parts. It makes me think that the problem was about sticky grease, dirt or so.
    If the lens show an irregular aperture -only when closed-, or one side more pronounced than the other, I think it could be a quality or a design issue... some lenses show this odd shape at one or two stops from wide open, but not at half or at any other aperture. I try to remember that some of my Nikkors show this behavior, and they are ok. I think it`s just an "unperfect" design.
    What I wanted to mean is that a bit of misalignment is not a problem, maybe it can be perfectly aligned or simply it`s into tolerances; I don`t know. But if the diaphragm show the blades wide open, as I can see in the highlight spots you linked, I think the misalignment is obvious, so I `d say it should be sent to be serviced.
    Obviously, if the blades are somewhat blocked, a service could benefit the shape when closed, but you can still have that irregular or non circular shape at certain apertures.
    I don`t have this lens, so -wide open- I cannot assure if it is normal to show the issue, or if it has such a bad design. I cannot believe Nikon made that botch, sincerely. Again, other than wide open, I think it could be "perfectly" right.
    Right now I`m at work and I only have enlarger and some quality LF lenses here, the Rodenstocks show a perfectly smooth shape at all apertures, the Scheneiders have convex blades. I can check my Nikkors tonight.
     
  17. I think it is not right, in your pics you say it has been taken wide open. Ask Nikon.
    00cCeb-543908284.jpg
     
  18. I have just randomly checked a dozen of my Nikkors. Wide open, all of them show a perfectly circular opening, the blades are hidden behind the maximum aperture ring.
    If closed one stop, half of the lenses show the issue you`re describing, some jags are more pronounced in one side than in the other, usually at one stop from wide open. Some show even jags in all the blades, and others show a perfectly even and smooth aperture.
    It doesn`t matter if the diaphragm is 6, 7 or 9 bladed, new or old, very used or almost unused, fast or slow... there is no connection between them, other than being Nikkors, from pre-Ai to G lenses.
    Even the 14-24 and the 24-70 show a very slight uneveness in the aperture. Whatever the reason, is the way they work... BTW, I have just noticed that my `cron 35 asph is starting to show the blades when fully open... ;P
     
  19. Out of curiosity, I have checked some of my other lenses... only my 35mm lenses show this issue. Even my 11 or 12 bladed Canon 50/1.2 show a lot of spikes (in fact I think it was intended to have an "star looking" aperture). My few Pentax lenses are even more "spiky" than the Nikkors.
     
  20. It's not the fact that there is that jag or that the blades don't line up and you see the rounded tips of the aperture blades that drove my crazy. It's the fact that it's uneven. WHY NIKON?!?!?! lol, I don't really care if the lens is designed like this... everyone touts its legendary performance, I just thought it was a defect.
    I spoke to someone else too who said they had their lens repaired and rebuilt by Nikon because the back element was scratched and the focal column was sticking due to drop damage, and he said he got a totally rebuilt lens back that looks the same.
    [​IMG][​IMG]
    Plus I've found photos where people got the same lopsided bokeh from the aperture. It's jagged on one side and round on the other.
    [​IMG]
    Full size image here
     
  21. Well, the thing is to avoid light spots on background areas. I don`t mind if perfectly round, or jagged in one side... OoF highlight spots are always UGLY! ;)
    If it makes to feel yoou any better, my Leica M lenses, all from the super-expensive asph generation, have the worst aperture blades to my taste.
    By the way, if you want perfection, make a jump to a larger format. All my Mamiya lenses have perfectly smooth apertures, either in five or eight blades. All my Copal shutters have also nice apertures with their seven blades.
     
  22. The jags in the bokeh are not super noticeable when shooting wide open at f/1.4, and I'm calm now that I'm pretty sure they're manufactured that way.
     

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