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11-24-2012, 06:23 PM   #1
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Evaluating a used FA 28-70 AL f4 lens for separation

Hi folks,

I'd like to hear from folks who had the FA 28-70 AL f4 lens fail due to its infamous element separation. I have a line on a used one that I will check out on Monday. What should I be looking for to see if it's a good or bad copy?

I'd also be interested to hear from folks who have the F 35-70 f3.5 ~ 4.5 and the FA 28-70 AL f4 - which one do you like better, and why? I have the FA 20-35 AL f4 to cover the 28-35mm span, and I recently picked up a nice F 35-70, and I'm enjoying its close-focusing capabilities. Still, I'd like to try the FA 28-70 AL f4 as well -anyone already been through this particular choice?

Thanks in advance, all.

11-24-2012, 07:13 PM   #2
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I have both and I like the F35-70 better due to better build quality. My FA28-70 fell apart while unsrewing a rubber hood that was on a little too tight. Optically I think the F 35-70 is a tad better but not by much. I would stay way from it if you already have the F35-70.
11-24-2012, 08:16 PM   #3
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Element separation looks something like gasoline on a puddle. There will be a rainbow-colored effect, probably at the edges first. It will look like something you could clean or residue from a previous cleaning. An optical diagram shows glued pairs on either side of the aperture blades. I don't know which pair is prone to failure.
11-24-2012, 09:29 PM   #4
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I have both and prefer the F 35-70. Nothing really wrong with the FA 28-70 f/4 but I like the build quality and small size of the 35-70. You do get a little more range with the 28-70 though.

The only criticism I have of the 28-70 is it seems a little washed out, not as contrasty as I would like in some situations. But I do not have a hood for it and that might help.

11-25-2012, 03:33 PM   #5
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Thanks for the input, folks. Curious that the FA 28-70/4 seems to command a higher price than the F35-70, yet (so far) most seem to favor the latter over the former.
11-25-2012, 03:49 PM   #6
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Pretty close in test results...

Pentax SMC-F 35-70mm f/3.5-4.5
Pentax SMC-FA Zoom 28-70mm f/4 AL

The F 35-70 is noticeably smaller and has the quasi-macro ability.

Since you've already got the FA 20-35 and F 35-70, I probably would stand pat with the F 35-70 rather than go after the FA 28-70.
11-25-2012, 04:43 PM   #7
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QuoteOriginally posted by msatlas Quote

Since you've already got the FA 20-35 and F 35-70, I probably would stand pat with the F 35-70 rather than go after the FA 28-70.
What? and not buy another lens? There's this thing called LBA, you know...

The price for the FA 28-70 is low enough that I can easily recoup my costs if I decide to sell it (assuming it's a good copy and I purchase it). It would allow me to test the FA 20-35 vs the FA 28-70 at 28mm, and all three at 35mm. I suspect I'll stick with the F35-70 in the end, but part of the fun is playing with different options along the way.
11-25-2012, 05:10 PM   #8
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Element separation may look many different ways. Sometimes It can be blotchy, sometimes it can be like a rainbow, sometimes it can be very subtle! For instance, here is a picture of a Minolta Rokkor 58 1.2 I recently bought, thinking about convering and then ended up returning instead.



This was almost impossible to spot. Even if you look through the lens against a bright sky you could not see it. It only became apparent once I started inspecting it with a flashlight and not even then. Only under specific angles when the LED flashlight would hit that spot it would glow and reveal itself.

My point: Bring a flashlight

11-29-2012, 12:55 PM   #9
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QuoteOriginally posted by oxidized Quote

My point: Bring a flashlight
Yep - I have one on my keychain and it's been used to evaluate a few thrift-store treasures.

I ended up picking up the FA 28-70/4, but life's been too busy to test it out so far...
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