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09-26-2008, 10:20 PM   #16
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QuoteOriginally posted by thePiRaTE!! Quote
I think f1.0 is worth it. F1.4 is a steal. Its just that no one will take my money for an f1.0 in K-mount
I'm taking deposits

09-26-2008, 10:29 PM   #17
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The theories are that:

A) More lens elements = better.

B) The curved interface of the cemented elements in f1.4, vs the flat one on the f1.7, is better

C) When stopped down to ~f1.7. the f1.4 will perform better than the f1.7 wide open.

Make of them what ye will.
09-27-2008, 04:01 AM   #18
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QuoteOriginally posted by lithos Quote
A) More lens elements = better.
This is not always true. More elements can be better for correcting abberations, curvilinear distortions, etc. but a simpler lens can outperform a more complex one if it is better designed.
In the case of a zoom lens, more elements make the design more usable over a wide range of focal lengths, but can also complicate the formula so as to reduce its overall performance.
Consider the human eye - sure, its lens doesn't project a rectilinear image on the retina, but it's a good example of a very effective simple lens.

On the subject of f/1.4 vs. f/1.7: There's not a lot of difference between them, but it's simply nice to have the option of the extra speed and shallow DoF.
Plus 8 diaphragm blades are definitely better than 6.
09-27-2008, 08:59 AM   #19
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QuoteOriginally posted by lithos Quote
C) When stopped down to ~f1.7. the f1.4 will perform better than the f1.7 wide open.
I've actually heard the opposite claimed - that the 1.4 doesn't actually become as sharp until f/2. But I have no 1.4 to compare for myself.

09-28-2008, 09:07 AM   #20
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QuoteOriginally posted by Spongefingers Quote
...
Plus 8 diaphragm blades are definitely better than 6.
I agree with the rest of your post, but this last sentence is just opinion. Definite implies that 8 is really better somehow (how?).

QuoteOriginally posted by Marc Sabatella Quote
I've actually heard the opposite claimed - that the 1.4 doesn't actually become as sharp until f/2. But I have no 1.4 to compare for myself.
I'm still formulating my opinion as I shoot more at 1.4 with a couple of lenses. I also have a 1.8.

I undestand Lithos to mean that with a wider aperture, a lens can be stopped down achieving better performance than a lens that would need to be wide open to be at the same aperture. That an f4 lens wide open thus might not be performing as well as an f1.4 lens stopped down to f4. This is reasonable and makes sense as stopping down brings most lenses to a higher performance level, but I have some experience which differs from this. I have slower lenses (Voigtlander 90/3.5, 180/4) that are as sharp as any lens I've tried at the same aperture, stopped down or otherwise. Armed with these Voigts and enlarged RAW files, I think superior optic design trumps stopping down.

Regarding the 1.7 vs 1.4 (which can only be directly compared at f2.0 anways) All things being equal, I'd say they would probably be the same at 1.7, just that the 1.4 could let in a little more light and have a slightly narrower plane of focus if desired.

As far as f1.4 being softer, I say that as DoF narrows, it gets a lot harder to hit perfect focus. I notice a big difference between 1.8 and 1.4, and between 1.4 at 58mm and 85. If I fall on either side of perfect focus, there is a glow of diffusion on contrasted edges which looks... soft, and that perfect plane gets farther away with an 85 and harder to detect. The thing is, within that perfect focus plane lies nearly as sharp an image as the lens is capable. There is more diffusion of sharp lines at 1.4 than when stopped down over f2.0, but I believe most of the softness lies on either side of an unforgivingly narrow ideal plane of focus.

Last edited by thePiRaTE!!; 09-28-2008 at 09:15 AM.
09-28-2008, 09:22 AM   #21
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QuoteOriginally posted by thePiRaTE!! Quote
I agree with the rest of your post, but this last sentence is just opinion. Definite implies that 8 is really better somehow (how?).
bokeh is generally better when the aperture is as close to be a circle as possible... you can agrue w/ that of course.
09-28-2008, 09:34 AM   #22
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QuoteOriginally posted by thePiRaTE!! Quote
Definite implies that 8 is really better somehow (how?).
Bokeh. All else being equal, more blades means better more circular bokeh. Although rounded aperture blades help too, so it's possible a lens with fewer rounded blades might do better than one with more straight-edged ones.

QuoteQuote:
I'm still formulating my opinion as I shoot more at 1.4 with a couple of lenses. I also have a 1.8.

I undestand Lithos to mean that with a wider aperture, a lens can be stopped down achieving better performance than a lens that would need to be wide open to be at the same aperture.
Yes, in general, that is of course true. But I was referring *specifically* to the Pentax 50/1.4 and 50/1.7. And I've heard it stated - not just once or twice, but really, as the accepted conventional wisdom - that the 50/1.4 lenses from Pentax (M, A, and FA version) are *all* softer than the 50/1.7 lenses at 1.7.

QuoteQuote:
As far as f1.4 being softer, I say that as DoF narrows, it gets a lot harder to hit perfect focus. I notice a big difference between 1.8 and 1.4, and between 1.4 at 58mm and 85. If I fall on either side of perfect focus, there is a glow of diffusion on contrasted edges which looks... soft
Yes, I can see that effect with the 50/1.7 too. But in any case, the usual claim is that the 50/1.4 is softer even when both lenses are at f/1.7 - which is to say, they offer the same DOF. Could be that this diffusion is more noticeable toward the outskirts of the zone of acceptable focus on the 50/1.4.
09-28-2008, 09:43 AM   #23
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QuoteOriginally posted by deejjjaaaa Quote
bokeh is generally better when the aperture is as close to be a circle as possible... you can agrue w/ that of course.
I wouldn't argue, but I would state that I know its not true, heh. For example, I've taken a cut-out hexagon and inserted it after the last element in my VL125/2.5 and shot with it so I could get a hexagon shape instead. The bokeh is exactly the same, only the shape of the highlights changed to a hexagon instead of a circle. I prefer hexagons

Edit - for the sake of (preventing) argument, I would add that by Bokeh, I refer to the background blur, which is unchanged by the number of blades. The highlights are a matter of preference, altered by the number of blades and is subjective. Out of these facts, I am simply challenging how it could be said that more blades are 'better'. Its like saying green is better than blue, heh.


Last edited by thePiRaTE!!; 09-28-2008 at 09:50 AM.
09-28-2008, 09:55 AM   #24
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QuoteOriginally posted by Marc Sabatella Quote
I've actually heard the opposite claimed - that the 1.4 doesn't actually become as sharp until f/2. But I have no 1.4 to compare for myself.
I agree Marc. I remember seeing some comparison posts that show the 1.7 performing marginally better at 1.7 and 2.0 with results being comparable at 2.8 and beyond. As for the bokeh...I personally have no problem with the OOF rendering of my two 1.7s. However, if bokeh counts, I have only one place to go...the Jupiter-9


Steve
09-28-2008, 10:18 AM   #25
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I have got to agree with Marc and Steve... at least as far a sharpness goes. I have the FA 50 1.4 and Fa 50 1.7 (dont ask!) and the FA 50 1.7 does seem sharper at 1.7 and F2... I have not done real tests, just observations... I am not a tester.

But I also have a S-M-C tak 50 1.4 that gets as much use as either of the FA's. I tend to use it in lowlight mostly and I trust my MF more than the auto focus of the FA wide open. Or at least when I miss focus I am not as upset as if the AF misses focus. 8^(
I just get so frustrated with the FA 50 1.4, sometimes it focus's on a face spot on at F1.4, but too often it is off.. the AF with shallow DOF is less than stellar... IMHO

I would just play with that smc tak of yours and you will know if the 1.4 is critical to you or not.

good luck
09-28-2008, 10:23 AM   #26
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QuoteOriginally posted by thePiRaTE!! Quote
The bokeh is exactly the same, only the shape of the highlights changed to a hexagon instead of a circle.
Edit - for the sake of (preventing) argument, I would add that by Bokeh, I refer to the background blur
you can't exclude highlights, sorry...
09-28-2008, 10:25 AM   #27
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QuoteOriginally posted by thePiRaTE!! Quote
\Its like saying green is better than blue, heh.
yes, it is - our eyes say so
09-28-2008, 10:29 AM   #28
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QuoteOriginally posted by stevebrot Quote
However, if bokeh counts, I have only one place to go...the Jupiter-9
how did it happen that you do not like cheap 20-something mm lenses w/ 5 blades
09-28-2008, 10:37 AM   #29
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QuoteOriginally posted by Marc Sabatella Quote
...But I was referring *specifically* to the Pentax 50/1.4 and 50/1.7. And I've heard it stated - not just once or twice, but really, as the accepted conventional wisdom - that the 50/1.4 lenses from Pentax (M, A, and FA version) are *all* softer than the 50/1.7 lenses at 1.7.

...But in any case, the usual claim is that the 50/1.4 is softer even when both lenses are at f/1.7 - which is to say, they offer the same DOF. Could be that this diffusion is more noticeable toward the outskirts of the zone of acceptable focus on the 50/1.4.
I think one of the factors that contributes to this conventional wisdom is the f1.7 lenses have a flatter field. Pentax states that in their literature, recommending the f1.7 lenses for copy work instead of f1.4s. It's hard enough to test for sharpness, but a curved focus plane makes it more annoying. I recall Viking79 doing a very good test on dpreview a few months ago which demonstrated the sharpness difference.

While the FA is still available at $200 new, it has kept the rest of the 50s at reasonable prices. It's not a bad idea to purchase several options and try them out, then sell off the ones that son't work out. The only risk is ending up like me, unable to decide among them.
09-28-2008, 11:13 AM   #30
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QuoteOriginally posted by deejjjaaaa Quote
you can't exclude highlights, sorry...
? I mentioned them specifically...

QuoteOriginally posted by deejjjaaaa Quote
yes, it is - our eyes say so
lol.

Funny thing is, I can't argue with that. Perhaps green is better than blue for you. I'm simply suggesting people are misinformed that it actually matters beyond shape, which is subjective.

Regarding the 1.7 vs the 1.4 as specific Pentax lenses, I can't say as I've only used an FA1.4 for a few shots and haven't ever used a 1.7. I was only speaking to the apertures size vs performance generally.
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