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04-27-2010, 10:01 AM   #136
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QuoteOriginally posted by Gene Temple Quote
Most likely the FA50 1.7 I got from VaughnA..........he probably wants it back. However the Sigma 10-20 has a degree of sharpness I really like as well.
I do want it back....Want to trade for a Sigma 28mm F1.8?

I don't have any primes except for the Sigma so I have to go with my 10-20 as well.

04-27-2010, 10:02 AM   #137
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No way Jose!

Hey Vaughn, you can borrow it anytime you want!
04-27-2010, 02:12 PM   #138
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QuoteOriginally posted by ismaelg Quote
This is an intereting topic.
Is the "newspaper on the wall" a good test for comparing center to corner sharpness?
I'm thinking of tripod mounted camera as perpendicular as possible adjusting for a similar field of view as needed.
Would that be a good test?
You should be aware of field curvature. Some lenses are designed to avoid this, so everything a fixed distance away from the film/sensor plane maintains the same focus. Some lenses aren't designed to eliminate it. That's one difference between an A50/1.4 and an A50/1.7.

A lens with soft corners might just have lots of field curvature. That will be more apparent at close-distance tests of flat subjects at large apertures. You can use focus bracketing to check for it - altering the focus from slightly front-focused to focused to slightly back-focused. If any of your images show the corners sharper than the center, the lens has field curvature. It's more of a testing issue than a real-world issue, but shouldn't be mistaken for just poor corner performance.
04-27-2010, 03:30 PM   #139
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That's always going to be a broad spectrum of choices - great variety seen here! My choices...

Ultra Wide Angle:
DA 12-24, no question. Great landscape/architecture lens too.

Macro:
The FA* 200/4 Macro - brutally sharp and beautiful bokeh... so sharp it may cause bleeding, even wide open... Works well as a telephoto too.

Super Telephoto:
The FA* 300/2.8 and the FA* 250-600/5.6 are some of the sharpest super telephotos (zoom or prime) I've ever used. Sharp wide open too.

So far, the images I've taken seem to prove this although I suspect as I improve, so will the images (hopefully/maybe)...

Cheers,
Marc

04-27-2010, 03:35 PM   #140
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Sigma 50mm f2.8 macro... It's the older mf version but it takes extremely sharp pictures.
04-28-2010, 12:19 AM   #141
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QuoteOriginally posted by Votesh Quote
At f1.4 I don't think any lens, from any manufacturer, could beat the A* 85. Match it maybe, but not beat it. It is a microcontrast monster. That said, I sold mine and kept my FA* 85 because the FA* is nearly as sharp at all apertures, with much less PF on digital.
16-9.net concluded the same when testing the A*85/1.4 against the Canon 85L/1.2 MkII (http://www.16-9.net/lens_tests/pentax85/index.html):

"That is an immensely impressive capture by the Pentax SMC A – wide open, against the Canon half a stop down. You'll have to excuse me while I go a bit purple here, becuase that is the sharpest 'corner' I ever seen any lens produce at this aperture (f1.4). Just stunning."

"All over again we see better contrast, resolution and colour in the corners of a 400D frame from the Pentax. The SMC A* just makes the Canon look bad, any honestly it isn't: I've not tested anything the 85L didn't embarrass at wide apertures, but it has truly met its match in the shape of the A* f1.4."
04-28-2010, 12:25 AM   #142
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QuoteOriginally posted by kerrowdown Quote
For me it's gotta be one of two, either SMC Pentax A* 85mm F1.4 or SMC Pentax-A* 135mm F1.8, I can't see which has the edge.

They both work for me.
I'll have to cast my vote for the A*135/1.8 (I'm not fortunate enough to also own the A*85). It is incredibly sharp at f1.8.
04-28-2010, 12:26 AM   #143
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DA70mm limited... probably one of the sharpest lenses ever made according to photozone.

04-28-2010, 12:32 AM   #144
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Tamron 90mm f2.8 - Macro
Pentax DA 50-135mm - non macro
04-28-2010, 12:42 AM   #145
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This is going to sound absolutely ridiculous but I sometimes test the sharpness of my lens by photographing my LCD screen. The more moiré I see, the sharper the lens seems to be. Can anyone else verify that?
04-28-2010, 01:03 AM   #146
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QuoteOriginally posted by hangu Quote
This is going to sound absolutely ridiculous but I sometimes test the sharpness of my lens by photographing my LCD screen. The more moiré I see, the sharper the lens seems to be. Can anyone else verify that?
This seems valid - I have heard of using moire interference patterns to test for AF accuracy.
04-28-2010, 02:02 AM   #147
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QuoteOriginally posted by photogerald Quote
I'll have to cast my vote for the A*135/1.8 (I'm not fortunate enough to also own the A*85). It is incredibly sharp at f1.8.
You really do need to get one, also get the hood as well, I wrote a review of this lens on the site here singing its praises.
04-28-2010, 01:22 PM   #148
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QuoteOriginally posted by xGene Quote
I always found the 15 "quite soft" at any aperture (on both the K7 and K2) in the corners and edges, and "softer than expected" in the center.
First, if you really find it softer than expected in the center, I'd be thinking about how you are testing with respect to subject size. Obviously, a shot of a person from 10 feet away won't show as much detail with the 15 as with a longer lens. That's why I decided to standardize on a a single subject at a single size, and portraits - while far from ideal - were the most practical choice for me. So the first I'd do is do that comparison, to see if your DA15 really is underperforming relative to other lenses you might have. For reference, here's a quick self-portrait I took the other day, showing the whole frame to give you an idea of the subject size I am using:



And here's a 100% crop from a conversion (using ACDSee Pro 3, which honors my +1 in-camera sharpness setting by applying a modest amount of sharpening, which it wouldn't have by default otherwise):



This should at least give you an idea whether we simply have different expectations, or whether yours is actually underperforming.

QuoteQuote:
If you have a chance, please tell me what sort of subject you would use for this purpose. as you indicated, portrat would not give you a fair idea of edge sharpness.
Judging border/corner sharpness on a wide angle lens, especially at large apertures, is indeed tough, and I don't have a great method of evaluating it. That's pretty much in keeping with the low importance I place on wide open border sharpness anyhow. But when I've successfully found sharpness on borders when shooting wide open, it's generally been shooting scenes that are basically two dimensional (nothing *way* in front of or behind the focus point but have do some depth to them - like trees with many branches, or rough groupings of objects that are lined up more or less like a wall but not totally flat. The idea being that I want objects of (somewhat, but too extreme) varying distances from me along the borders, in hopes that *something* along that border will be in focus.

For instance, here's a shot of a cliff face. It's like a brick wall but with things sticking out in front of and behind the focus plane. This is shot wide open at f/4, resized to show you the whole scene:



Here's a 100% crop from the extreme border at 3:00:



It would have been sharper stopped down of course, but somehow, I just don't find much to complain about in that crop. It's certainly sharper looking to me than most of the samples I see posted to illustrate how soft the borders supposedly are. Yet if I scroll around and check out other spots along the border, most of them are *not* in focus; I kind of got lucky with this particular outcropping.

So if I really wanted to test border/corner sharpness, I'd be looking at shooting similar subjects - essentially flat, but with just enough variation in subject distance along the border to give me a good chance that something is in focus.

Last edited by Marc Sabatella; 04-28-2010 at 01:31 PM.
04-28-2010, 03:05 PM   #149
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I am often amazed by my Sigma 10-20/3.5. Pretty weak at 10mm in the extreme corners, but really shines at 11-20mm. Crop from the thumbnail.
(wide open, no PP done, I think the sharpness setting is -1)
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04-28-2010, 07:35 PM   #150
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One other entry to my "sharpest" list - DA*200. Playing around with it the other day and took a shot of an office mate just to show him what it would do, and you could count the pores on his skin (much like Mark's shot above). Very sharp.
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