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12-16-2008, 01:18 PM   #1
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Does your 50mm look like this?!?

I'm making an effort to find out if other copies of the smc P-FA 50mm F1.4 lens exhibit the same feature or if mine is problematic.

I've been using my copy of this lens for more than a year and I'm noticing a problem that appears to have been around since I got the lens. I found the problem because I've been trying to get those nice, round out of focus highlights that are so popular with holiday shots and portraits.

It seems that one or two aperture blades on my copy are a fraction slower to close than other blades. Or that there's a blade or two that closes too quickly. Not sure which...

Here's what the lens looks at f22:



Notice how the blades form an uneven shape in the center.


at f2:



You can see that there is not a smooth transition from one blade to another on one side of the lens, giving little "spikes." These shapes form distortion on the images, readily apparent below.


and f1.7:


This shows more easily how one side of the lens seems to be moving more than another side.

Of course, at f1.4, all is good, since the lens is wide open.


Here's what an image looks like at f2:



I checked against an old f2 50mm lens I had kicking around and while it has only 6 blades, there were still some issues with "spikes" showing around the edges at the first two stops. My 135 and the SDM lenses I have don't seem to have the same issue.

I'm curious now... do other copies of this lens seem to show the same behavior?

12-16-2008, 01:37 PM   #2
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that is definitely not normal. I'm not even sure if i's possible for just one blade to be a litle loose. But yeah, not normal...
12-16-2008, 01:48 PM   #3
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Mine doesn't look like that to my eye at f22, but f2 does give those spikes.
12-16-2008, 01:56 PM   #4
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You could infect your other lenses with this condition- you should mail it to me for quarantine Seriously though, I don't think it is anything to worry about. I looked at my a 50mm 1.4 and it does the same kind of thing.

12-16-2008, 02:32 PM   #5
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To have all the blades "spiky" is normal.

To have all the blades "smooth" is normal.

To have a mix of both is not normal, but doesn't seem to warrant repair/return/complaints, in my opinion. I love when my gear has "character" other peoples' gear doesn't.
12-16-2008, 02:47 PM   #6
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It is actually pretty normal. There was another thread here about this same subject last summer, I think.
12-16-2008, 04:28 PM   #7
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QuoteOriginally posted by pasipasi Quote
Mine doesn't look like that to my eye at f22, but f2 does give those spikes.
I don't think he's talking about the spikes. If you look closely the rightmost vertical blade seems a bit off...
12-16-2008, 04:53 PM   #8
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QuoteOriginally posted by smigol Quote
I'm curious now... do other copies of this lens seem to show the same behavior?
I have some lenses with apertures like that. My Pentax-A 50mm f1.4 happens to have blades that all move at the same time. The spikes are part of the blade shape, and pretty common for all Pentax lenses.

I think the aperture design is likely to include a bit of slack just to allow free blade movement, and normal slack from the manufacturing process is causing the distorted shape.

I would be reluctant to attempt repair myself, partly because it's major disassembly, partly because the mechanism is delicate and partly because there might not be anything to fix.

12-16-2008, 06:34 PM   #9
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Interesting. My M series 50mm f1.4 only shows spikes, equally distributed, at f 2 and the next half stop. The rest is smooth and even. But I do have an ancient Makinon 28-80mm that exhibits the same problem as yours - very noticeably out of whack on one side. I know it's like comparing a Morris Minor with a Rolls Royce, but I guess it shows it's not an uncommon fault. I can understand your fretting about it, (and now you'll be looking at every photo you take with it through a microscope!), but as others have said it's probably best to leave it alone.
12-16-2008, 09:42 PM   #10
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QuoteOriginally posted by dave sz Quote
I don't think he's talking about the spikes. If you look closely the rightmost vertical blade seems a bit off...
Am I the only one seeing this?
12-16-2008, 10:18 PM   #11
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QuoteOriginally posted by dave sz Quote
Am I the only one seeing this?
Have to admit, I don't really see exactly what you're referring to...

My F 50 1.7 and M 50 1.7 have blades pretty much like that, and I'm pretty sure others I have that aren't right in front of me now do also.
12-16-2008, 10:25 PM   #12
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QuoteOriginally posted by jsherman999 Quote
Have to admit, I don't really see exactly what you're referring to...

My F 50 1.7 and M 50 1.7 have blades pretty much like that, and I'm pretty sure others I have that aren't right in front of me now do also.
I'd agree I've had and still have some lenses that do this and others that don't it's never caused an issue that I've noticed.
12-17-2008, 01:20 AM   #13
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I have to thank every one that responded to the thread.

What I've gotten from this is that it appears that every lens has some sort of oddness about how it performs and I've found a lens that has some "character."

Seeing how I have other lenses that exhibit the same kind of "spike" feature, I'm fine with their performance. The uneven-ness of how the blades close is something that I'm not happy about, but I may eventually learn to maximize, especially since I know the orientation of the pattern.
12-17-2008, 04:03 AM   #14
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I have noticed a number of my lenses doing this (non-circular aperture) from time to time. Most distressing was the DA*300 which had various odd shaped apertures for the first hundred shots or so. I had teardrop and half moon OOF highlights in a number of shots. Orientation was not consistent. It seems to have gone away with use but occasionally I still see a flat sided highlight. I think the blades were a little tight when brand new. Generally the fewer blades, the less the lens does it.
12-17-2008, 06:55 AM   #15
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QuoteOriginally posted by smigol Quote
I'm making an effort to find out if other copies of the smc P-FA 50mm F1.4 lens exhibit the same feature or if mine is problematic.

I've been using my copy of this lens for more than a year and I'm noticing a problem that appears to have been around since I got the lens. I found the problem because I've been trying to get those nice, round out of focus highlights that are so popular with holiday shots and portraits.

It seems that one or two aperture blades on my copy are a fraction slower to close than other blades. Or that there's a blade or two that closes too quickly. Not sure which...

Notice how the blades form an uneven shape in the center.

I'm curious now... do other copies of this lens seem to show the same behavior?
My FA50/1.4 looks pretty much the same as that. If I need round OOF highlights I shoot with a different lens. The Nokton 58 is very nice for this, though much more flare prone.
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