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04-12-2007, 05:09 AM   #1
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Soft at f2.8?

Hi,

I received the Vivitar Series 1 28-90mm yesterday and played around with it quite a lot on the K100D. I took several shots at f2.8 and couldn't really tell how it performs as I don't have any benchmark (this is my first lens that can go f2.8). So I'd like to ask your opinions on the quality of the attached picture. Is it too soft? Do you see any other issues? The picture's taken indoors, no flash, using a tripod, at f2.8, ISO400.

Thanks.

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04-12-2007, 05:55 AM   #2
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Is this a 100% crop or the whole picture re-sized?
It doesn't look too soft to me - just with a very narrow DOF.

BTW, I owned that lens and it is a stellar performer. I only sold it because it was too heavy.
04-12-2007, 06:07 AM   #3
roy
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i've got the non-series 1 kiron/vivitar 28-85. it's a stellar lens. weighs a ton tho.
here's a 100% crop at f2.8.


here's some 100% resizes shot wide open. with flash.
28, 50, 85mm


one thing you will need is a lens hood unless the S1 has one built in. i got a 3step rubber one on ebay delivered for 10usd.

enjoy,
roy
04-12-2007, 11:17 AM   #4
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Thanks for the kind words for the lens. It is heavy, but is also fun to play with and learn.

Below is the 100% cropped picture.

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04-12-2007, 11:23 AM   #5
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QuoteOriginally posted by seeker Quote
Thanks for the kind words for the lens. It is heavy, but is also fun to play with and learn.

Below is the 100% cropped picture.
Yea the depth of field is very narrow especially at the closest setting. See how the moustache area is very sharp?
04-12-2007, 05:29 PM   #6
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So I take it that the short or narrow DOF is a characteristic of a wide aperture? Would it be the same way with fast primes, e.g., 50/2.0, 50/1.7, and 50/1.4?

Fyi, the image below is 100% crop of a different picture in the similar shooting setup, except that the aperture is f5.6 of f8. The picture seems to be noticeably sharper.

Thanks as always!
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04-13-2007, 08:13 AM   #7
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The smaller the aperture number the shorter, tighter the depth of field. But different lens focal lengths are another factor in the DOF equation. A wide angle lens at f2 has more depth of field than a 200mm lens at f2.
04-13-2007, 09:49 AM   #8
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Looks like you got a terrible copy of the lens... really really really soft. I know that this news really upsets you, so why don't you just box up the lens and send it to me so you won't be reminded of your horrible purchase...

04-13-2007, 12:52 PM   #9
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i can't tell from these which is the sharper. i do know that the 28-85 is rated at one site as being on a par with the smc FA* 28-70 f2.8 but $1000 less expensive.
04-14-2007, 05:46 AM   #10
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Yeah, I'm so concerned that I'm thinking of getting a longer one just to compare...
04-14-2007, 03:26 PM   #11
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to answer your original question, yes, it will be softer at 2.8, most lenses are like that... "f8 and be there" is how it's phrased?

here is how i understand it: when you hit that optimal f8 or whatever it is for a particular lens, things will be sharper because of the increased resolution, not because there is a bigger area that's in perfect focus.

however, more of the image will be in an acceptable focus range because of the increased depth of field, which i believe is called the "circle of confusion":
Depth of Field Calculator
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