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09-30-2017, 02:21 PM - 2 Likes   #31
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X-post from 300mm lens club. My initial tests with newly acquired Sigma APO DG Ex 1.4x tc.



These are my first tests, Pentax K5, with my Adaptall 60B 300mm f2.8, compared against the adaptall 014F 1.4x tc, and the Kenko 1.4x tc I have had for a couple of years


All f2.8 (=f4 with tc). From top L: reference 60B, upsized 140%; 60B + 014F, 60B + kenko, 60B + sigma apo.




First tests indicate clear superiority for the sigma apo.
Addendum: the sigma is supposed to be restricted to use with selected sigma lenses, however apart from a reluctance to lock on, I haven't run into any issue using this so far with 60B + adaptall mount.


Last edited by marcusBMG; 09-30-2017 at 03:04 PM.
09-30-2017, 02:43 PM   #32
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Is it possible that there is a difference in the focus point or is that already verified to be accurate. This is a stunning result. Lovely detail with the APO converter.
09-30-2017, 03:00 PM   #33
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QuoteOriginally posted by UncleVanya Quote
Is it possible that there is a difference in the focus point or is that already verified to be accurate. This is a stunning result. Lovely detail with the APO converter.
it is always possible that there can be slight errors/discrepancy in focus. I was using visual focus with my 1.36x VF magnifier, corroboated with focus confirm and checked with live view. The crops are of the focus point ie the musselmens netting. My only solution is to repeat tests to confirm results - I'll be trying some test pics of one of the castle turrets as per usual when the weather allows, probably with the NX20 which, IMO, has more accurate focus than the K5 with strong magnification in the EVF.
10-01-2017, 06:18 PM   #34
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QuoteOriginally posted by marcusBMG Quote
it is always possible that there can be slight errors/discrepancy in focus. I was using visual focus with my 1.36x VF magnifier, corroboated with focus confirm and checked with live view. The crops are of the focus point ie the musselmens netting. My only solution is to repeat tests to confirm results - I'll be trying some test pics of one of the castle turrets as per usual when the weather allows, probably with the NX20 which, IMO, has more accurate focus than the K5 with strong magnification in the EVF.
Very impressive results. Great effort and write up.

10-02-2017, 05:57 AM   #35
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Thanks UV. I'll be posting more detailed results as and when..
10-07-2017, 03:53 PM - 2 Likes   #36
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Castle turret test pics. I was going to use the NX20 but forgot, so K5 again.








This time I would say the 014F has produced the best images, and the sigma the worst! Reason? Operator error mostly probably...
10-09-2017, 10:24 AM   #37
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QuoteOriginally posted by marcusBMG Quote
Castle turret test pics. I was going to use the NX20 but forgot, so K5 again.

This time I would say the 014F has produced the best images, and the sigma the worst! Reason? Operator error mostly probably...
Does the K5 have a magnified live view option? I don't think it does - that may help. I'm interested in this topic as it shows that in the baseline practical use the operator makes more difference perhaps than the device.
10-09-2017, 10:39 AM   #38
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QuoteOriginally posted by UncleVanya Quote
Does the K5 have a magnified live view option? I don't think it does - that may help. I'm interested in this topic as it shows that in the baseline practical use the operator makes more difference perhaps than the device.
Yes live view on the K5 goes to 10x (press the info button). However the clarity of the LV image doesn't really improve - it doesn't seem to be a "zoom in", more of a digital magnification of the non magnified LV image. This is why I get better focus with my mirrorless Samsung NX20 - the magnified 7x focus assist IS a "zoom in". However as I already mentioned above I do use LV a lot, with a loupe if I am really trying to nail the focus. However with the best will in the world there is still an element of estimation - to and fro-ing with the focus onto a middle "best focus" position.
One cause of error when I am using a bean bag is inadvertent nudging of the focus position when changing f-stop with the aperture ring.
Anyway I would tend to agree with you - focus accuracy can only be as good as the discriminatory limits imposed by the visual signals from the camera, and the eyesight and technique of the operator.
I'm going to do some indoor test images with one of my macro lenses.

10-11-2017, 12:52 PM - 2 Likes   #39
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More tests

Well I thought that a reasonably careful test with a tamron 52BB 90mm f2.5 macro lens might discriminate something..
Samsung NX20, focus using macro rail and 8x magnification. Test subject my trusty swiss banknote. Light was a bit dull, boosted with a halogen table lamp.



f2.5. Lens alone crop is not resized - I moved the tripod back with the tc's to get same field of view.




F5.6




For what its worth careful scrutiny suggested the kenko is slightly softer. It is certainly slightly down on magnification, something I had noticed when I first got it - more like 1.37x.

Last edited by marcusBMG; 10-13-2017 at 03:26 PM.
10-13-2017, 12:34 PM - 2 Likes   #40
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The Sigma APO tc was increasingly reluctant to lock on - it's described by sigma as being specifically for certain select sigma lenses, I thnk its made this way - so I took a jewellers file to the locking pin and took off a few thou from the pins trailing edge, which fixed it.

I redid the test pics (see post #31) of the musselmens nets.
K5. All f2.8 (=f4 with tc). From top L: reference 60B, upsized 140%; 60B + 014F, 60B + kenko, 60B + sigma apo.



The more I try, the less I can distinguish between these tc's.

Last edited by marcusBMG; 10-13-2017 at 03:26 PM.
10-13-2017, 01:45 PM   #41
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May I ask which TC you had to modify?
10-13-2017, 03:23 PM   #42
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QuoteOriginally posted by jeallen01 Quote
May I ask which TC you had to modify?
The sigma - I have clarified my previous post for those of you who haven't been folowing the whole thread.
10-14-2017, 08:42 AM   #43
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QuoteOriginally posted by marcusBMG Quote
The sigma - I have clarified my previous post for those of you who haven't been folowing the whole thread.
Thanks - am interested because when I use the Sigma TC with the 100-300 F4, it sometimes fails to lock into place correctly and the combo won't AF until I slightly loosen the lens-TC or TC-body joints and relock it/them.

Wonder if it is a similar problem - will have a word with Sigma Imaging UK to see if they can shed any light on the problem.

BTW, don't suppose you have a photo of what you did to the pin on the T/C so that I can compare that with my "untouched" version?
10-14-2017, 09:33 AM   #44
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I just shaved the pin slightly with a fine file, on the trailing edge as I said ie the "rear end" sense as you rotate the tc to lock in place. I did a test by marking the end of the pin with a black marker, this suggested the pin was catching the lip of the slot on the lens mount on that side. A pic isn't really helpful..
02-12-2018, 09:54 PM   #45
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Hi I am looking to get a tc for my K1 for my 100macro and my 150-450. Since its ff I am not sufe about these old tc. Is the 1.4 better or a 7 element 2x? Can someone recommend the best avabile pleas
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