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03-18-2017, 01:00 PM   #1
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What is going on with this lens?

I'm on copy #2 of the D-FA 28-105 and am testing it out. I was setting up in a pool area (concrete floor) with a tripod and noticed as I moved the lens's focus ring to get the scene out of focus, it would capture more of the setting. Take a look at the left edge of the scene. There is a white doorway there. When the image is out of focus it is visible, when the camera autofocuses (or I manually focus) the doorway is no longer visible.

No, the tripod didn't get knocked or vibrate out of its position. Because I carefully moved the focus ring back out of focus and the further out of focus you go, the more of the door I can see. I could make this happen at will going back and forth with the focus ring.

I also wasn't touching the zoom ring. And, even if I had (which I did not), the camera autofocused so my hands weren't anywhere near the lens itself for the in-focus shot.

What is happening there??


Last edited by mee; 09-22-2017 at 04:39 PM.
03-18-2017, 01:02 PM - 1 Like   #2
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QuoteOriginally posted by mee Quote
What is happening there??
Focus breathing.

What is ‘focus breathing’ and how does it affect your images?
03-18-2017, 01:10 PM   #3
mee
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QuoteOriginally posted by bertwert Quote
Focus breathing.
So I see. Well that's odd.
03-18-2017, 01:34 PM - 1 Like   #4
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Stand back! Water leak in the wall...gonna blow any second?

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03-18-2017, 01:42 PM   #5
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that is horrendous barrel distortion - is that typical of that lens? I had the FA version, but I don't remember it being that bad.
03-18-2017, 01:49 PM   #6
mee
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QuoteOriginally posted by ffking Quote
that is horrendous barrel distortion - is that typical of that lens? I had the FA version, but I don't remember it being that bad.
Unsure. Was mostly testing AF microadjustment there but was only about 4 or so feet away from the wall.
03-18-2017, 01:58 PM   #7
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This is a new optical design, I believe, and isn't really a "version" or derivative of the FA type. It looks kind of typical for this lens per the PF in-depth review;

HD Pentax-D FA 28-105mm F3.5-5.6 ED DC WR Review - Distortions | PentaxForums.com Reviews
03-18-2017, 02:52 PM   #8
mee
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btw I went back for a few more shots and just got "shook down" by a police officer taking my sample photos haha (well he was friendly but very very questioning).

Said there was a woman that looked like she was headed to the (completely desolate) pool.. and saw me out here with a camera and thought that was odd. There was no woman headed to the pool. I guess people with cameras are some kind of sickos or something that need to be questioned... not the creepoids with the tiny cameras or hidden smartphones. I explained what I was doing, he shook my hand and walked away, I kept taking my test shots. So I finally had a police interaction.. and I didn't end up on an episode of COPS.

03-18-2017, 03:29 PM   #9
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Definitely nothing wrong with the lens, but the vignetting is something you need to learn to live with. It's easily corrcred. For snapshots, the in camera JPEG profiles work wonders.

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03-18-2017, 04:21 PM   #10
mee
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QuoteOriginally posted by Adam Quote
Definitely nothing wrong with the lens, but the vignetting is something you need to learn to live with. It's easily corrcred. For snapshots, the in camera JPEG profiles work wonders.
No one mentioned anything about vignetting. One guy said it looked like a lot of barrel distortion and I was concerned by what I know now as 'focus breathing'.

The vignetting is easily corrected though. Lightroom adjusts instantly with a single click of the Lens profiles box.
03-18-2017, 05:25 PM   #11
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QuoteOriginally posted by mee Quote
No one mentioned anything about vignetting. One guy said it looked like a lot of barrel distortion and I was concerned by what I know now as 'focus breathing'.

The vignetting is easily corrected though. Lightroom adjusts instantly with a single click of the Lens profiles box.
Just saying, in general, that's the only practical issue with the lens. IMO the distortion is acceptable for the focal length/format. And you're absolutely light about LR.

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03-18-2017, 08:37 PM   #12
mee
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QuoteOriginally posted by Adam Quote
Just saying, in general, that's the only practical issue with the lens. IMO the distortion is acceptable for the focal length/format. And you're absolutely light about LR.
Yes sorry that came out a little rough.

Soft corners are more of an issue to me.. and the sharpness drops off the edges too. On both copies I've had. Ironically I think the 2nd copy might be a little worse than the first at least in one corner. Leaning towards just keeping it though.. I don't think most people really care about edge to edge sharpness when they rate such a lens and when they say 'its sharp edge to edge' they really have no clue what that means or their bar is set lower than mine with this. And I suspect the elusive 'sharp edge to edge' copy is probably 1 out of 10 at best.
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