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03-02-2009, 08:28 AM   #1
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Why some lenses are worth the price.

About a year ago i bagged on the Ziess 18mm F3.5, well, even though i havent used it, i take my words back.

here is a photo using a Sigma 18mm F2.8 on a full frame camera, even at F5.6 you can see how quickly the image deteriorates in the corners/sides

the Sigma cost me 140 bucks, compared to the ziess price of around 1500 USD.

I expect that the Ziess will not exhibit such degradation, hence the price.

On digital however its a moot point, as most of that softness becomes hidden due to cropping.


Which i think everyone should keep in mind when talkinga bout Pentax's current DA lineup of glass. Its much easier to make optics that cover a small image circle with edge to edge perfection.

If the DA40 was constrcuted to fill a full frame, even at its current aperture size, and maintained its quality, i can assure you it would cost much more than it does now.


again, this is not OOF, this is edge softness.




Last edited by Gooshin; 03-02-2009 at 08:48 AM.
03-02-2009, 08:51 AM   #2
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QuoteOriginally posted by Gooshin Quote
Which i think everyone should keep in mind when talkinga bout Pentax's current DA lineup of glass. Its much easier to make optics that cover a small image circle with edge to edge perfection.
I don't really look for edge softness, but wouldn't edge softness be cropped on FA lenses, but not on DA lenses? Since the DA's are designed for the smaller imaging surface, I figure they'd be just as susceptible to edge softness on APS-C as FA lenses are on 35mm film.

That's just a guess though.
03-02-2009, 08:54 AM   #3
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QuoteOriginally posted by rfortson Quote
I don't really look for edge softness, but wouldn't edge softness be cropped on FA lenses, but not on DA lenses? Since the DA's are designed for the smaller imaging surface, I figure they'd be just as susceptible to edge softness on APS-C as FA lenses are on 35mm film.

That's just a guess though.
there is nothing to crop on the DA lenses though, they are made as is.

i could be wrong though, in my head i envision a different formula for APC-S (or smaller) lens design, with the elements being smaller and thus flatter.
03-02-2009, 09:43 AM   #4
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QuoteOriginally posted by rfortson Quote
I don't really look for edge softness, but wouldn't edge softness be cropped on FA lenses, but not on DA lenses? Since the DA's are designed for the smaller imaging surface, I figure they'd be just as susceptible to edge softness on APS-C as FA lenses are on 35mm film.

That's just a guess though.

Maybe with the smaller elements, the designers can afford to put in a little 'extra' while still maintaining compact size. But again, edge sharpness seems to be an issue in wide and ultra-wides, and whether 135 or APS-C, both lenses are pretty bulky and need large glass unless the speed is kept down. Probably why quite a few of the earlier f/3.5 variants were sharper than the f/2.8's or f/2's

Pretty much all the APS-C ultra-wide zooms are a stop slower than their pro FF counterparts, and tokina's 11-16mm sacrifices zoom range for the speed. Where are the 28, 24, 20, 18 or14mm equivalent 2.8 primes for APS-C? We have the DA 14, and the DA 21. I don't think other brands have any offering outside fisheyes and f/4 zooms untill you hit the old film 20-24mm lenses, or a $$$$ full frame 14mm.

03-02-2009, 10:35 AM   #5
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QuoteOriginally posted by Gooshin Quote
there is nothing to crop on the DA lenses though, they are made as is.

i could be wrong though, in my head i envision a different formula for APC-S (or smaller) lens design, with the elements being smaller and thus flatter.
I'm probably not explaining myself very well. What I meant (in general, I have not experimented with this) is this:

A) FA+full frame = edge softness potential
B) DA+APS-C = edge softness potential
C) FA+APS-C = less edge softness potential

Therefore (in general) A=B, and A>C.

C is true because, as you and others have said, the APS-C sensor is only using the "sweet spot" of the lens, and any edge softness falls outside the boundaries of the sensor.

Again, I'm just speaking in generalities, so feel free to point out where/how I'm mistaken.
03-02-2009, 11:41 AM   #6
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QuoteOriginally posted by Gooshin Quote
About a year ago i bagged on the Ziess 18mm F3.5, well, even though i havent used it, i take my words back.

here is a photo using a Sigma 18mm F2.8 on a full frame camera, even at F5.6 you can see how quickly the image deteriorates in the corners/sides

the Sigma cost me 140 bucks, compared to the ziess price of around 1500 USD.

I expect that the Ziess will not exhibit such degradation, hence the price.
Regarding the Zeiss lens, I read a review of it in a Swedish magazine recently. And the corner(FF) is very good wide open, and some improvident at F8!!
A highly recommended lens, but at a steep price.
03-02-2009, 01:42 PM   #7
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Your image has captured "the essence" of the scene. That is all that matters. Of course, my fellow photographers would be critical as usual since this is a hobby to obsess oneself in anything trivial.

I will say that your style of photography is pretty much street. "Sharpness" is not much of a concern
03-02-2009, 02:37 PM   #8
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Wow, that edge softness is really noticeable! It's an interesting effect, but definitely a good reason why the lens isn't expensive.

03-02-2009, 02:58 PM   #9
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The image is horrible (not the image, but the technical "quality" of the corners). It looks like my Pentax 28mm shift lens, fully shifted and used at its minimum distance - than it is at least as bad as this Sigma, but even on APS-C... (this is abusing the lens, but nevertheless I was surprised by how poor the IQ is.)

Sometimes it is amazing, what the industry tries to sell - and I bet, there are enough happy snappers using the lens and finding the images very good "considering the price", which is a lame excuse for crap.

Ben
03-02-2009, 03:21 PM   #10
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I don't really get what you are trying to say. The DA40 is inexpensive thus it must not be very good?
03-02-2009, 03:27 PM   #11
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Maybe I'm misunderstanding something. Are you shooting this picture from the boat? and is the boat moving? If so, wouldn't we expect "motion blur" in the parts of the scene that are *not* moving with the boat? That's what it looks like to me...
03-02-2009, 03:32 PM   #12
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QuoteOriginally posted by cousinsane Quote
I don't really get what you are trying to say. The DA40 is inexpensive thus it must not be very good?
if the DA40 was built to cover a full frame image circle, it would cost more money

if it was built to cover a FF image circle, and maintained its comperative edge to edge sharpness, it would cost alot more money.

the DA40 is cheap because it is designed for APS-C (well that and because its f2.8, requiring smaller glass, making the QC better)
03-02-2009, 03:35 PM   #13
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QuoteOriginally posted by Marc Sabatella Quote
Maybe I'm misunderstanding something. Are you shooting this picture from the boat? and is the boat moving? If so, wouldn't we expect "motion blur" in the parts of the scene that are *not* moving with the boat? That's what it looks like to me...

motion blur at 1/1000?

do you not see the effect on the people?

do you not see the effect on the sail going up?

Last edited by Gooshin; 03-02-2009 at 03:41 PM.
03-02-2009, 03:41 PM   #14
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"Why some lenses are worth the price."

I think it's a much more interesting and difficult question to ask why some lenses are not worth the price.
03-02-2009, 03:42 PM   #15
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QuoteOriginally posted by wildman Quote
"Why some lenses are worth the price."

I think it's a much more interesting and difficult question to ask why some lenses are not worth the price.
okay then start your own thread, durr.

thanks for crapping in mine with an open ended question leaving behind a trail of confusion and anxiety.

Also, i wasnt asking, i was telling, my observations...
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