[audiobomber]

About one shot in fifty I've experience an unreasonable amount of hunting. It's actually worse than that, because sometimes I shoot MF. At lunch today I shot about 30 photos with no trouble, and the last one as I was coming into the house, I couldn't get focussed. It was a dark bird on a silver chimney against the sky, aperture set at F/7.1. The AF could not lock, it seemed to try to focus, then back up (or out), then start over again before it reached the sweet spot.

I just took the camera out again to see if I could reproduce the problem (no bird this time), and I couldn't. Focus locked in quickly, no matter whether it was from coming from a closer point or infinity. I'm stumped. It should not have had trouble focussing the first time either. Nor with the other few shots it's had trouble on.

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Last edited by audiobomber; 06-19-2008 at 02:28 PM.

[audiobomber]

CA (green, if this is CA) exists slightly, but you'll need to pixel peep

I'm seeing a bit of PF. I don't know whether you'll see it at this resolution, but in photo of the flicker, the branch on the right has a purple fringe. The hermit thrush shows quite a lot of CA in the background.

[OniFactor]

has anyone tried the 55-300 on a film camera, to see what kind of FF coverage it has?

[J.Scott]

I took my DA 55-300mm out last night to see if it did excessive hunting for focus. On one occasion it pulled all the way in then all the way out before it locked on target. The subject - a tiny sparrow on the bird feeder - was small and dark and the background was also dark. I tried to follow a bumble bee in the roses but my hands shake too much to keep the focus dot on the creature, so it moved a bit then - but not excessivly.

[AML]

These were taken from the other day. I'm still getting alot of out of focus shots, but when i can get it to focus properly, it doesn't do too bad. Lighting wasn't ideal.
All shots taken at F6.7 with spot metering.

A magpie playing peek-a-boo's from behind a tree.



Mr gull.

[audiobomber]

Great pics AML. What I love about the lens is the colour rendition, and your photos show it off beautifully.

I did take a few shots I like, not just those ugly ones I posted above.

[SpecialK]

First day. Like the IQ. Will edit post later to include operational handling after this weekend...


Attachment 14228

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100% crop of above
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Pentax 50-200 vs 55-300 vs Sigma 70-300. The long...
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and short of it.
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Last edited by SpecialK; 06-04-2015 at 08:03 PM.

[selar]

[QUOTE=AndrewG NY;265118]There's no reason that your aperture setting should affect autofocus. It's probably in your head.
QUOTE]


I have personal experience with a Sigma 14mm EX that changed focus at f4.5, i.e. AF was spot on till f4.5, then at f5, it would focus closer, all this on a tripod, pointing at same high contrast feature on a wall etc.

I lived with the problem for nearly a year, then just as warranty was about to expire sent it in for repair. Sigma replaced the chip (after some resistance) and now it behaves normally.

I have heard reports of other lenses behaving similarly, can't recollect which, but it might be the PTX 12-24.

Apparently, its a technique lens makers use to reduce CAs.

[Class A]

Sorry, wish I could help--my only suggestion is to try to think of other explanations--AF and metering are both always done at max aperture. Lens doesn't stop down until just before the shutter fires.

It is true that the lens doesn't stop down until just before the shutter fires but apparently -- at least for some lenses -- the camera takes the target aperture into account when calculating AF.

On my Tamron 18-250, a target aperture of f/3.5 will cause the camera to refocus at 18mm, from a focus that was obtained at 250mm (the lens is not parfocal, I think). When I set the target aperture f/8, the focus adjustment will not happen (even though AF still occurs at the maximum f/3.5 setting). Apparently the camera reckons that with f/8 (more DOF than f/3.5), the target is already in acceptable focus.

Not sure if this observation applies to what has been discussed in this thread but certainly it is not true that the set (target) aperture does not matter for AF.

[Bramela]

I have used this lens for a couple of months now and have found it to be a decent lens for its price.
Hunting? I havent had major problems with hunting, only when it is moved from a subject at much different range, it then seems to go right in then right out and then settles on the focus.

PF : none, in my experience.

Sample, taken just today with K10d and DA 55-300



Would I recommend this lens : Yes ! for its light weight and its economy price. Results are pleasing as well. Yes there are better lenses, but usually at a much higher price (eg : DA*200 or 300)

#Further to the above : I just went out and tried the focus again. Late afternoon, half sunlight, focussed at varying distances in quick succession (8ft to infinity) and lens found focus very quickly without any real problem.
Perhaps I have a good copy, but to date it hasn't caused me much problem at all.
(Note: I am not biassed in favour of this lens, just saying as I see and experience it!(

[losecontrol]

Well....i still see the fact. Longer focal zoom-range=less quality.
That's why we spend huge money in buy our beloved Pentax-Prime Lenses right?

Regards

Emil

[asdf]

Pentax...what's up? If I want one AF lens for the occasional wildlife, why does my old n crusty FA dominate the DA?

That's a rather odd statement to make, since you did not actually shoot wildlife with 55-300, but stuff around your house; also, you only compared one aspect. Both lenses' AF fails for some wildlife photography, because neither of them has SDM--in-camera AF is loud enough to scare away some timid animals. For occasional wildlife, with practice, a good mirror lens (with MF) would probably suffice.

[audiobomber]

PF : none, in my experience.

Sample, taken just today with K10d and DA 55-300

That is not the type of photo where PF would show, there's very little contrast. Try a bare branch with a backlit bird where you have to use +1 EV to expose the subject. You'll see some PF on the branches in the background. It's well enough controlled; i.e. not as much as the Tamron 70-300, but more than the DA*300. I agree that it's not a problem but it is a characteristic of this lens.

PS I'm certainly not bashing the 55-300mm. I love the ergonomics, the colour depth and the sharpness, even wide open; it's amazing value and a very good lens. It does tend to hunt more than it should and it can produce fringing in high contrast situations. Perfection is simply not available for $300.

[Norwegian Blue]

I played around with the 55-300 a bit in the garden during the christmas holiday. The light was not the best, and I forgot to bring my tripod. I'm still quite unexperienced with DSLR, but the 55-300 seems like a good lens (at least for my needs). The sharpness is pretty good, and the CA is not that bad.

[ryan s]

Wow...this is kind of an old thread

That's a rather odd statement to make, since you did not actually shoot wildlife with 55-300, but stuff around your house; also, you only compared one aspect. Both lenses' AF fails for some wildlife photography, because neither of them has SDM--in-camera AF is loud enough to scare away some timid animals. For occasional wildlife, with practice, a good mirror lens (with MF) would probably suffice.

If the 55-300 can't lock on to stationary targets, I don't see a need to take it further?

Side by side, the FA is faster, more accurate, hunts less, and locks on to the appropriate target more and better than the DA. This is "measurebation" in a controlled environment...and I was hoping the "new" and "better" tech would beat up on my antique. It didn't. IQ aside, why buy an aperture-ring-less lens if the AF sucks?

To update this thread...I'm now considering going after an MF 300mm and probably a 135 or 200mm as well. I don't use AF on the FA like I though I would...like I thought I would need. Not that the FA isn't good...it's takes nice pics for $150.