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09-30-2009, 03:29 PM   #61
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QuoteOriginally posted by CFWhitman Quote
I think you are generalizing too much here.
In lenses of similar quality sharpness will usually be better, but that's as far as I would go. As an example where even that is not generally considered true, look at the Pentax F 50 1:1.7 compared to various Pentax 50 1:1.4 lenses. Most people say that the f1.7 lens is sharper at f1.7 than the f1.4 lenses are at f1.7. This may be the exception to the rule, but it shows that you can't just assume that the faster lens will always be sharper at the max aperture of the slower lens.
My opinion :
If you want to make a 1.4 lens, upscaling a 2.0 design will lead to aberrations which are unacceptable, so they add complexity (glass, aspheric surface etc.) to surpress these aberrations better, and get an acceptable perfocmance at 1.4.
This usually means that stopped down to 2.0, this will be a better corrected lens then the 2.0 lens.
What happens if you scale up the 1.4 design to an 1.2 lens, you can see in the pentax 50/1.2, a perfect example of exploding aberrations at 1.2
I admit that adding more glas can hurt contrast (but excelent coatings came to the rescue)
Another effect of adding more glass and complexity, is deteriorated closeup performance when the design becomes strongly assymetric.
Thats where the simpler 2.0 designs outclass the 1.4 versions.


QuoteOriginally posted by CFWhitman Quote

Seriously, lenses have a definite effect on the color of the resulting photos. You'll see people mention often that a certain manufacturer's lenses tend to have a warmer or colder rendering than the lenses of another manufacturer, and this is true. If you keep all the other factors the same, and merely switch lenses, you will see differences in color rendering. Auto white balance tends to hide this to some extent, but it is definitely there.
QuoteOriginally posted by Douglas_of_Sweden Quote
Because glass are not so clear as you believe and light are a bit more complex.
Different colors (different wavelengths) have different refractive index. This is what cause Chromatic Abberration when different colors have different focus points, but it also do other things with the difference between what enters the lens and what leaves it in the other end.. But this never work perfectly and each manufacturer has a bit different multi-coating methods and this gives a different final effect on how the colors comes out.
So lens design, glass quality and coating properties all influence the color character you get from a lens. Long before sensor/film does.
My opinion:
Take a lens (but not a takumar which suffers from yellowing), point it at a white cloud an look through it.
You will see probably a very light color cast, caused by the coatings/glass properties as mentioned above, I will not deny that.
Now take a skylight filter, which is a very mild color filter.
You will see that this mild filter has a much stronger color cast than the lens.
Now, take a 80A filter, a strong blue filter which was used to use daylight film under tungsten light.
Ever seen a lens with such a color cast ? And with a simple selection of another white balance we achieve in our DSLR the function of that 80A filter.
Conclusion: any slight color cast of a lens has become completely irrelevant.
If that is not enough, bring one negative to a print shop, then to another shop, or even the same printshop. I think that the difference between the color of the prints of the same negative are greater than any difference in lens color cast could ever achieve.
Same is true for 2 different (uncalibrated) monitors.

What I think is that when someone tells that he likes the colors of a lens,he really means that he likes the contrast of the lens.

Then about purple fringing, this happened also on film, only to a lesser extend.
I think that the current sensors are more sensitive to the blue part of the spectrum than film.
I cannot prove this, because I have not yet found a graph of the sensitivity versus wavelength for pentax camera's

George

10-01-2009, 09:56 AM   #62
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QuoteOriginally posted by glasbak Quote

My opinion:
Take a lens (but not a takumar which suffers from yellowing), point it at a white cloud an look through it.
You will see probably a very light color cast, caused by the coatings/glass properties as mentioned above, I will not deny that.
Now take a skylight filter, which is a very mild color filter.
You will see that this mild filter has a much stronger color cast than the lens.
Now, take a 80A filter, a strong blue filter which was used to use daylight film under tungsten light.
Ever seen a lens with such a color cast ? And with a simple selection of another white balance we achieve in our DSLR the function of that 80A filter.
This discussion is way off topic, but color rendering is not the same as color cast. My Sigma 50 Macro has a warm color cast, but the rendering is pretty neutral (similar to the human eye). My Jupiter-9, on the other hand, has distinctive color rendering that at times is somewhat unnatural. It is difficult to describe, but it is almost as if it transmits colors in a way that is not usually evident to the eye and/or with an intensity that was not in the original subject.

QuoteQuote:
Then about purple fringing, this happened also on film, only to a lesser extend...
I have been shooting film for a long time (40+ years) and have never seen anything even remotely resembling PF...blue/yellow CA for sure, but no PF. When I first started digital a few years back, tendency to show PF was always treated as a sensor issue and a discussion of such was included on most camera reviews. For sure, there is an optical component (some lenses are more prone to invoke PF), but it is not a matter of the optics being poorly corrected in the usual sense. I guess it would be fair to say that PF is characteristic of the current state of the technology. With any luck, future sensors/image processors will be immune.

Steve
10-01-2009, 12:03 PM   #63
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Guys, thanks for the interesting insights. I'm still learning a lot from you, so please keep sharing your knowledge!

It's bad weather and dark outside, so I have again made some wide-open shots (the A* was stopped down to f/1.8 because otherwise the DOF would be super thin, and of course it then becomes sharper). Pentax K-7 on tripod; focusing was done through magnified Live View on the green applique. Shot in RAW; the white balance of the A* was applied to the other shots. So if the lenses have a color cast you should be able to see it. Or so I hope

If I'm doing things right, please let me know. If I'm doing things wrong then please also let me know.















10-01-2009, 12:57 PM   #64
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QuoteOriginally posted by stevebrot Quote
T
I have been shooting film for a long time (40+ years) and have never seen anything even remotely resembling PF...blue/yellow CA for sure, but no PF. When I first started digital a few years back, tendency to show PF was always treated as a sensor issue and a discussion of such was included on most camera reviews. For sure, there is an optical component (some lenses are more prone to invoke PF), but it is not a matter of the optics being poorly corrected in the usual sense. I guess it would be fair to say that PF is characteristic of the current state of the technology. With any luck, future sensors/image processors will be immune.

Steve
Well, you need to overexpose a lot on film to get PF.
I am not convinced by the argument that if a lot of magazines say so, it must be true.
If it is not a function of the lens, and only caused by the sensor, it should happen with any lens. And that is not the case, even between similar focal length lenses at similar apertures, there can be differences in PF.
So the silicon sensor detects something what is hardly registered by film, and comes out of the lens.
The theory that PF is caused by chromatic aberration and a different color sensitivity of silicon sensors makes sense, for me at least.


QuoteOriginally posted by Asahiflex Quote
So if the lenses have a color cast you should be able to see it. Or so I hope

If I'm doing things right, please let me know. If I'm doing things wrong then please also let me know.
I cannot comment on the color rendering right now, because I am not behind my CRT, but behind a notebook LCD where the color rendering highly changes with the viewing angle.

10-02-2009, 04:10 AM   #65
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Here are some shots made with the Asahi-Kogaku 83mm f/1.9 Takumar which is a M42 remounted M37 Asahiflex version. Actually the M37 mount is still intact; only a M42>M37 ring was added (fixed with a very small screw). So it's reversible if I want to.



The pictures below are only trial shots (will try to take more interesting and diverse shots later today). However, I'm very happy with the output of the lens. It's sharp and constrasty, and that for a lens from 1957... Frankly I did expect softer results wide open (more like the 80mm f/1.8 Komura).

Shot in RAW and converted to JPG with Adobe Camera RAW. No PP (contrast etc.) other than resizing directly after converting from RAW and applying USM and the border. Just like I always do The 100% crop is not PP'ed in any way.

1. F/1.9


2. F/1.9


3. F/1.9


4. F/1.9


5. F/1.9


6. F/1.9


7. F/5.6


8. F/1.9; 100% crop from no. 6.
10-02-2009, 04:48 AM   #66
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QuoteOriginally posted by glasbak Quote
What happens if you scale up the 1.4 design to an 1.2 lens, you can see in the pentax 50/1.2, a perfect example of exploding aberrations at 1.2
"exploding aberrations"
10-02-2009, 08:59 AM   #67
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Finally three wide-open portraits with the 83mm f/1.9 Asahi-Kogaku Takumar. I think this lens is as good as anything out there





10-02-2009, 04:07 PM   #68
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QuoteOriginally posted by glasbak Quote
Well, you need to overexpose a lot on film to get PF...
Start another thread and show me. Should be simple enough...

...And I am not talking about a color cast on blown highlights...I want to see PF like what I get with my Zenitar 16...huge blue patches adjacent to in-focus, properly exposed subjects.

QuoteQuote:
The theory that PF is caused by chromatic aberration and a different color sensitivity of silicon sensors makes sense, for me at least.
It made sense to me the first time I read that theory (in the Wikipedia article I think), except that there are lenses with very low CA that none-the-less are prone to PF under certain conditions. The FA 77/1.8 limited is one of them (personal experience here...).

In any case, I am not willing to hijack this thread any longer. I know now what the OP meant by CA regardless of what label might be applied and understand why that is an issue for him with the A* 85.

Steve

10-02-2009, 04:59 PM   #69
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I can see why you like the 83mm. Those are very good portraits of a very cute (and apparently very active) little girl, noting the small wound on her forehead.
Sigh, I mostly do portraits but these wonderful lenses are all beyond me.
Thank you for showing us your work.
10-08-2009, 05:34 PM   #70
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QuoteOriginally posted by glasbak Quote
My opinion:
Take a lens (but not a takumar which suffers from yellowing), point it at a white cloud an look through it.
You will see probably a very light color cast, caused by the coatings/glass properties as mentioned above, I will not deny that.
Now take a skylight filter, which is a very mild color filter.
You will see that this mild filter has a much stronger color cast than the lens.
Now, take a 80A filter, a strong blue filter which was used to use daylight film under tungsten light.
Ever seen a lens with such a color cast ? And with a simple selection of another white balance we achieve in our DSLR the function of that 80A filter.
Conclusion: any slight color cast of a lens has become completely irrelevant.

George
Take a 12 year aged single malt isla whiskey and a 3 year old blended whiskey and mix them both with coca cola and there wont be much difference either.

And if you drink enough to get drunk, the hangover will feel the same.

Despite this I prefer the single malt any day.
10-08-2009, 05:35 PM   #71
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Awesome shots!

And the 83mm holds our well against the others!

QuoteOriginally posted by Asahiflex Quote
Finally three wide-open portraits with the 83mm f/1.9 Asahi-Kogaku Takumar. I think this lens is as good as anything out there





10-09-2009, 05:09 AM   #72
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QuoteOriginally posted by Douglas_of_Sweden Quote
Take a 12 year aged single malt isla whiskey and a 3 year old blended whiskey and mix them both with coca cola and there wont be much difference either.

And if you drink enough to get drunk, the hangover will feel the same.

Despite this I prefer the single malt any day.
Nonetheless, you should try Te Bheag, the only blended I have ever enjoyed, which is made on the Isle of Skye with Talisker as a dominant component. Much cheaper, however, and the blend actually improves Talisker for some who find its pungent burn overpowering.

But drink it with coke? Sacrilege!
10-09-2009, 05:17 AM   #73
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QuoteOriginally posted by rparmar Quote
Nonetheless, you should try Te Bheag, the only blended I have ever enjoyed, which is made on the Isle of Skye with Talisker as a dominant component. Much cheaper, however, and the blend actually improves Talisker for some who find its pungent burn overpowering.

But drink it with coke? Sacrilege!
I agree...it was supposed to be a parallel to some sacrilege statements about lenses.

Never tried the Bheag, but it sounds interresting. I'm willing to try anything from the Isle of Skye.
Besides Isla single malts, I've got an Irish fav: The Connemara peated single malt. Have you tried it?
10-09-2009, 05:39 AM   #74
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Connemara is nice but I have known no Irish person to drink it! Also good is Red Breast pot stilled. I admit to drinking Powers as well, which is sweet but perfect for a hot whiskey.

That Tak 83 looks very useful! (On-topic comment guiltily inserted.)
10-09-2009, 08:07 AM   #75
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Great performance of FA 77
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