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04-22-2011, 12:59 PM   #1
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FA43 asymmetrical aperture blades

Hey B&H,

so I bought an FA43 a month ago, which I realize is probably way out of your return policy, but I just wanted to see what my options are... My FA43, when stopped down, has asymmetrical aperture blades. At f3.2 or so, half of it is jagged and the other half is more smooth, also, one side is "stopped down" more than the other side (it comes into the diaphragm deeper, making the aperture a bit smaller than it shuold be/offcentered)?

If you can do anything to help (repair/replace?) Please do let me know. Again, I do realize this is quite a bit after 14 days (about double that or so...)

04-22-2011, 05:46 PM   #2
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QuoteOriginally posted by jaieger Quote
Hey B&H,

so I bought an FA43 a month ago, which I realize is probably way out of your return policy, but I just wanted to see what my options are... My FA43, when stopped down, has asymmetrical aperture blades. At f3.2 or so, half of it is jagged and the other half is more smooth, also, one side is "stopped down" more than the other side (it comes into the diaphragm deeper, making the aperture a bit smaller than it shuold be/offcentered)?

If you can do anything to help (repair/replace?) Please do let me know. Again, I do realize this is quite a bit after 14 days (about double that or so...)
Does the pics look fine to you? This seems to be normal for alot of lenses. My FA 50 (I think it's that one) also have asymmetrical blades at f/2.8 ish, but it never bothered me, even when looking carefully at the bokeh. The light coming in also doesn't seem to be affected much by it.

Of course how much asymmetrical blade affects the picture depends from lens to lens... How does the blades look at f/8 or so?
04-22-2011, 09:18 PM   #3
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This is rather common with the FA43. I had to rearrange mine to get an almost symmetrical shape. To make it worse, the shape will actually change as the lens is rotated. Good luck on finding a perfect copy.
05-04-2011, 11:58 PM   #4
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Thanks for the above replies. So I take it there's nothing on the B&H end that can be done about it?

Also, @wlachan, how'd you manage to fix yours? Was it difficult?

05-05-2011, 12:14 AM   #5
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It's not difficult, just takes time to sort out the best possible order. However, if you have never repair lens before, I am reluctant recommending it.
05-05-2011, 05:21 AM   #6
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I'd be quite reluctant to open up the FA43. I suppose that ghostless coating must be similar to what nikon calls nanocristal coating. The thing can be quite fragile and if you dirty the element, forget about wiping it cause that coating will be wiped off as well.
Not sure on which element it is, so you might never have a problem to reach the aperture blades, but then again you might.
05-05-2011, 06:44 AM   #7
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Hello;

I've forwarded your comments to Pentax Japan. I will post what they have to say on your issue.

C h u c k C a p r i o l a
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Thank you, we appreciate your business.
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05-05-2011, 07:43 AM   #8
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Thanks very much chuck, looking forward to their reply (:

Wlachan - if it's not too difficult and Pentax can't do anything for me, I wouldn't mind giving it a shot....I'd practice about a dozen times on, say, an old tak or something just in case though. Not identical, sure, but it would give me some sort of feel of opening up a lens :T


So far my experience in fiddling with this kind of stuff is limited to swapping out focussing screens in my k-x.

05-05-2011, 10:24 AM   #9
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QuoteOriginally posted by Spare Tire Quote
I'd be quite reluctant to open up the FA43. I suppose that ghostless coating must be similar to what nikon calls nanocristal coating. The thing can be quite fragile and if you dirty the element, forget about wiping it cause that coating will be wiped off as well.
I am not sure about Nikon, but traditionally SMC is quite tough. My only experience with coating came off was an old FA*300/4.5. I didn't know what kind of treatment it had received though.

QuoteOriginally posted by jaieger Quote
Wlachan - if it's not too difficult and Pentax can't do anything for me, I wouldn't mind giving it a shot....I'd practice about a dozen times on, say, an old tak or something just in case though. Not identical, sure, but it would give me some sort of feel of opening up a lens :T
So far my experience in fiddling with this kind of stuff is limited to swapping out focussing screens in my k-x.
The FA43 is simpler to disassemble but the phase of rearranging the aperture blades might smear or scar the inner glasses if your fingers slip. But if you must, just start disassemble from the front. You can leave the rear intact. My best advice is try to live with it if not severe, or send it to the service centre hoping the tech will spend the time fixing it properly.
05-05-2011, 11:02 AM   #10
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QuoteOriginally posted by wlachan Quote
I am not sure about Nikon, but traditionally SMC is quite tough. My only experience with coating came off was an old FA*300/4.5. I didn't know what kind of treatment it had received though.



The FA43 is simpler to disassemble but the phase of rearranging the aperture blades might smear or scar the inner glasses if your fingers slip. But if you must, just start disassemble from the front. You can leave the rear intact. My best advice is try to live with it if not severe, or send it to the service centre hoping the tech will spend the time fixing it properly.
It's not that it's overly severe, at f2.5 it's tolerable...f2.8-f4, I quite dislike, and since that's when it's as its sharpest...and it's not even that. I paid for premium glass and just want to get the most of out of it
05-05-2011, 04:47 PM   #11
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QuoteOriginally posted by wlachan Quote
I am not sure about Nikon, but traditionally SMC is quite tough. My only experience with coating came off was an old FA*300/4.5. I didn't know what kind of treatment it had received though.
The FA43 doesn't just have SMC coating. They advertise this "ghostless coating" also and i supposed it must be something else.

Here's some info on Nikon's nano crystal coating:
Nikkor Lens Technology
05-06-2011, 06:05 AM   #12
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Hello,

As promised;

If the lens is past B&H’s return period it should be sent into our shop (which is C.R.I.S.) along with a copy of the sales receipt, and a note with the customer’s name, address, phone and a description of the problem.

The address for our shop is:

PENTAX Service Department
250 North 54th Street
Chandler, AZ 85226

877 269-7179

Chuck
05-06-2011, 04:13 PM   #13
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QuoteOriginally posted by jaieger Quote
It's not that it's overly severe, at f2.5 it's tolerable...f2.8-f4, I quite dislike, and since that's when it's as its sharpest...and it's not even that. I paid for premium glass and just want to get the most of out of it
I feel your disappointment and if you were in my area, I might fix it for you. Since you are past the exchange period, perhaps just send it to Pentax service centre and hope for the best. Limited lenses are well designed and well made, but sadly Pentax assembling QC is just not as tight as I hope for.

This is how mine looks after rearranging the blades myself. One blade is still closes a little more than it should be but much better than b4.
05-06-2011, 06:44 PM   #14
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QuoteOriginally posted by wlachan Quote
This is how mine looks after rearranging the blades myself.
Oh, the "lovely" jaggies. Too bad the Ltd. lenses cannot avoid showing them. My Sigma 28/1.8 EX doesn't have them. Sadly, my Sigma 70/2.8 shows them a little bit as well. Maybe it depends on the widest aperture diameter whether they can be avoided or not?

Alan, could you please (perhaps in another thread you could link to from here) explain what "rearranging" of the blades means? How can one actually influence the overall shape? By exchanging blades for another? I'd be grateful to you if you could share your knowledge with us.
05-06-2011, 07:04 PM   #15
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This lens consists 8 aperture blades and they actually aren't 100% identical if examined carefully due to manufacturing tolerance. Also, the slots holding these blades in place have slight loose fit. The end result is that the actual aperture shape between lenses is inconsistent and unpredictable during the assembling process, and is also changing as the lens is being rotated. Fine tuning the shape is simply too time consuming at the factory so many Pentax lenses have asymmetrical aperture. What I did was simply removed all blades and rearrange them randomly till it looked (almost) symmetrical, for both landscape & portrait orientation. There is no guarantee what the end result might be but as least cannot be any worse. This is not a difficult process to those with repair experience, but unfortunately out of reach for average consumers.
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