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150-450mm focus adjust

Posted 17/07/2016 - 21:25 Link
Ive been finding my 150-450mm a bit soft at 450mm f5.6. So I took a couple of shots of a chart (which I had to colour in the focus point with black pen), focusing with liveview on, using back button focus and 2sec delay while mounted on a tripod. The chart was roughly 45 degrees to the lens.
Im not 100% sure but it looks like its focusing OK perhaps slightly front focusing?

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Question is, is this enough to account for the loss of sharpness shown in the thread below or is this lens faulty?
Edited by NeilP: 17/07/2016 - 21:39
Posted 19/07/2016 - 07:24 Link
Couple of real world shots to demonstrate the issue. At 270mm:
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At 450mm. Note the lack of fur detailComment Image

I suspect there may be a lens issue
Posted 19/07/2016 - 08:08 Link
Does it make any difference using the focus buttons on the lens?
Posted 19/07/2016 - 09:35 Link
My reading suggests that a number of owners found the lens soft at the long end, but noticed improvement when stopped down to 6.3 and 8.

Equally, a number say it's very sharp wide open at the long end, so lens variation, technique, who knows?

It's a rare lens that performs really well wide open. Most lenses have their sweet spot a couple of stops down.

Your lens tests look in focus but soft. If you can, maybe try another copy of the lens, or the lens on another body?
Edited by JohnX: 19/07/2016 - 09:48
Posted 19/07/2016 - 10:19 Link
I'm having similar issues with my new 150-450mm. I used it for the first time last Wednesday taking nearly 500 shots with my K-3.
I found shots taken at around 400mm seemed much clearer & sharper than at 450mm (see my thread 300mm v 150-450mm).
I sent some sample images to SRS and waiting to see what they think.
Posted 19/07/2016 - 12:46 Link
That target doesn't look much good as a test for sharpness.

Try something with fine detail such as beer bottles.

Roof tiles although at a longer distance than wildlife are good for checking focus and sharpness.

450mm should not be soft.

You could change it for the excellent Sigma 150-500mm F5-6.3 APO DG OS HSM which is superb at 500mm f/8 1/320th on a tripod. SR works and is often needed on a tripod at this length.

K-5 100% Crop from JPG just a touch of sharpening
500mm f/8 1/320th : 400ISO

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Pentax K-1 + K-5 and some other stuff

Edited by Algernon: 19/07/2016 - 12:56
Posted 19/07/2016 - 22:12 Link
I think you're right Neil, it is front focussing very slightly. At this focal length that will make all the difference between 'sharp' and 'not sharp', which is one of the reasons why I stick with the DA*300mm. With Primes, there's no variable focussing dependent on focal length, an issue that has plagued me on zooms. You can adjust, but will invariably end up with accurate focussing at one focal length and inaccurate at another.

However, I would add that it's worth repeating your test several times, as I have found with my lenses that I often get variances on the same lens at the same focal length on the same target! If you get this all you can do is take the best average.


PS I disagree with Algi, I don't see a problem with the subject you are using to test this.

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Some cameras, some lenses, some bits 'n' bobs
Posted 20/07/2016 - 08:10 Link
In the K-1 you can apply AF fine adjustment to the individual lens, don't know about other bodies.
Posted 20/07/2016 - 13:04 Link
You can fine tune most of them especially K5, K3 & K1 models. I use
Look for the auto focus adjustment chart on the right hand side and download it. I use on all my cameras to date and it works well....
Posted 21/07/2016 - 22:56 Link
Not found an issue with mine, It even bests my DA*300 + 1.4x TC. You have to be spot on with the focus though and very still. It's still not great focusing on moving targets when mounted on a K-3
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"Life is what happens to you while you're busy making other plans" (John Lennon)
Posted 22/07/2016 - 07:41 Link
One of the best moon shots I've ever seen

Posted 24/07/2016 - 17:49 Link
tyronet2000 wrote:
One of the best moon shots I've ever seen

Thanks Tyone
"Life is what happens to you while you're busy making other plans" (John Lennon)
Posted 01/08/2016 - 10:25 Link
Neil what was the outcome with the lens did you exchange it. I had similar issues at the weekend with a number of focus issues and blurred and soft shots. Many thanks adrian
Posted 01/08/2016 - 17:42 Link
Ive been waiting for a weekdn when I can actually get to watford. Not contacted SRS yet, not sure how gwb67
got on?
Posted 02/08/2016 - 07:00 Link
NeilP wrote:
Ive been waiting for a weekdn when I can actually get to watford. Not contacted SRS yet, not sure how gwb67
got on?

Thanks Neil for the update Iam sure what to do with my lens yet either.

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