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Old Dec 21, 2007, 9:03 PM   #21
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These two lenses will not arrive until next Friday. I will post some pictures. Thanks all.
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Old Dec 22, 2007, 6:01 AM   #22
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lomitamike wrote:
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Oh, you know that as soon as you open the box you just got to play with it.

Here's the very nice lady that was happy to see me get this lens that I've been looking for a long time.

This was the first photo I shot with my new lens. Right out of the camera only downsized.
Very nice! It's always a smart move to get the proper approvals in place before making the investment. :-)
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Old Dec 28, 2007, 10:00 PM   #23
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Two blue days!

I received the 85/1.4 few days ago and could not wait any longer to test the lens, but felt bad right away. The sound of auto focus was very lound and also back focus more than 10mm. I finally returned the lens for the refund.

The brand new Sony 50/1.4 from B&H also came this morning, unfortunately, this lens also back focus 10mm at 1.4 and 5mm at 2.8 (auto focus), no problem at all when use manual focus. I will call B&H to arrange the return. The sharpness of this lens at wide open is much better than both 50/1.7 I have at wide open.

The two 50/1.7, one old (used) and one new version (brand new) don't have any focus problem at all on my 5D and A700.

Any suggestion?
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Old Dec 29, 2007, 11:21 AM   #24
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lsifs; That's very unfortunate. Can you tell me how you came to determine the backfocusing @ 10mm for both lenses?

Specifically what autofocus setting were you using?

With the 85 I,ve never owned one but I have played around with one (original)on my camera and it was noisy as you described. That's a pretty bigand heavy piece of glass to be moving back and forth.

Hope the refund goes smooth with the 85. It's a bit risky buying from ebay.

I don't think B&H will be any problem
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Old Dec 29, 2007, 12:29 PM   #25
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Lomitamike: I have received the refund from the eBay seller, will call B&H next Monday.

The way I test the focus is to stack 7 books (at least 5), let them standvertically on the table or desk, each book has the thinckness of approx. 10mm, with all the side title of the booksface to the camera, eachapart 5mm behind the the left one, so the most left one has the closest distance to the camera. For this test, I use tripod, set the camera at spot AF, turn off AS, ISO 400, no flash, the distance must be at least the minimum focus distance of the lens.

I focus on the middle one (book #4), if the book#4 has the best focus compare with the book #3 and #5, then this lens has no FF or PF problem.

If the focus is on the book #1, this lens has FF by 15mm, #2 FF by 10mm, #3 FF by 5mm, #5 BF by 5mm, #6 BF by 10mm, #7 BF by 15mm.

Do you have better way to test the focus?

For the 85/1.4 AF focus noise, not only it was lound, but the sound was not smooth, I think the gear inside the lens needs lubrication.
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Old Dec 29, 2007, 1:33 PM   #26
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That's my preferred method (the way you tested it with books).

What lighting did you test it in? Sometimes, the temperature of the lighting can impact Autofocus.

What camera?

With two lenses backfocusing like that, I'd suspect the camera. You'll have a shallower Depth of Field at f/1.4, and if the camera's AF sensor alignment is out of tolerance, it may not be as apparent with your other lenses.


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Old Dec 29, 2007, 1:55 PM   #27
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lsifs wrote:
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For this test, I use tripod, set the camera at spot AF,

Do you have better way to test the focus?

No.

It sounds like you are very thorough. I just wanted to be sure you were using "SPOT" AF.

Just out of curiosity, do you check all of you lenses? how do they focus?

I've only played with my 50mm lens to get an idea os how shallow a 1.7 DOF is. It did focus where I aimed.


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Old Dec 29, 2007, 3:58 PM   #28
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Happy to know that I used the right method. I used this method to test all the prime lenses that has F2.8 orfaster on my 5D and A700, including the 50/1.7, 50/1.7 RS, 24/2.8, 28/2.8, 135/2.8, Sigma 105/2.8, 200/2.8, all of them did focus on the spot. But the Sigma 30/1.4 has 5-10mm BF on both 5D and A700.
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Old Dec 29, 2007, 7:53 PM   #29
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I'm curious. What is the mechanism of failure that would cause a lens to have a focus offset? Am I wrong in thinking that the AF system operates as a closed loop that nulls the focus error?
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Old Dec 30, 2007, 11:39 AM   #30
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FrankD wrote:
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I'm curious. What is the mechanism of failure that would cause a lens to have a focus offset? Am I wrong in thinking that the AF system operates as a closed loop that nulls the focus error?
Frank; I do not uderstand the mechanics of the AF system but, I do know that thereare 3 screwson the bottoma 5D that if I'm not mistaken adjust the position/angle of the sensor. When screws are properly adjustedthey cause the camera to focus on target.

I'm wondering if the focus test that lsifsconducted with the books spaced evenly apart would have been more favorable if the books had been different colors(high contrast).

I've had my camera/lenses have difficulty getting to AF under low light / low contrast conditions.

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