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Archive 2010 · ROKKOR Telephoto Image Thread
  
 
Bifurcator
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p.4 #1 · ROKKOR Telephoto Image Thread


Yeah, I can name a bunch of MF lenses where there's no CA to be seen.


Jun 30, 2011 at 09:16 PM
sebboh
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p.4 #2 · ROKKOR Telephoto Image Thread


Bifurcator wrote:
And with that, I'm as confused as you are. I have a couple of hundred MF lenses and only a handful produce CA artifacts that show up in 100% screen displays. At 400% I can see more but that's kinda stretching things. Even a smaller handful yet produce PF. In almost all cases the the few with fringing and CA artifacts are slight enough that is would not show up at all in an 8x10 print out. Maybe in Double Quad Crown 60" x 40" (Movie Theater Poster) sizes it would be noticeable if you were to stand close enough
...Show more

i agree with you about lateral CA on in focus regions being generally not a serious problem, but loCA, or bokeh CA, or lateral color, or whatever it's called is prevalent in most of the lenses i've used. to be specific about what i'm talking about it's the purple fringing in the oof regions in front of the focus and green fringing in the oof regions behind the focus point. here's an example of it that is readily visible at websize with rokkor 135/2.8:





this is a particularly difficult kind of shot to avoid this type of CA with, but i see it to some degree in every narrow dof shot i've taken with a lens faster than f/2 and in every narrow dof shot i've taken with a telephoto that wasn't a zoom or apo.



Jun 30, 2011 at 09:16 PM
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p.4 #3 · ROKKOR Telephoto Image Thread


I get that too but I wouldn't say "most". Typically only lenses capable of f/1.4 or wider and then to varying degrees for each model. Sometimes it's quite strange... as the image is displayed in ACR briefly just before the demosaicing it's REALLY there (everything is totally fuzzy but the OOF CA colors are rich and bright) - then 2 seconds later when the image demosiacs and becomes sharp on-screen it's all (100%) gone. That's caused me to scratch my head on more than one occasion. But when I look at the ACR defaults for that lens/ISO anything that might do that is set to zero, or whatever.


Jun 30, 2011 at 09:24 PM
sebboh
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p.4 #4 · ROKKOR Telephoto Image Thread


Bifurcator wrote:
I get that too but I wouldn't say "most". Typically only lenses capable of f/1.4 or wider and then to varying degrees for each model. Sometimes it's quite strange... as the image is displayed in ACR briefly just before the demosaicing it's REALLY there (everything is totally fuzzy but the OOF CA colors are rich and bright) - then 2 seconds later when the image demosiacs and becomes sharp on-screen it's all (100%) gone. That's caused me to scratch my head on more than one occasion. But when I look at the ACR defaults for that lens/ISO anything that might
...Show more

maybe the way i shoot provokes it more. i have noticed that about ACR too, and i think part of their standard demosaicing algorithm corrects at least partially for PF.



Jun 30, 2011 at 09:33 PM
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p.4 #5 · ROKKOR Telephoto Image Thread


and or color fringes in general...

It's a strong probability as the visual cues suggest.



Jul 01, 2011 at 10:13 AM
Tomser
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p.4 #6 · ROKKOR Telephoto Image Thread


Very interesting to hear your about your findings .

sebboh wrote:
"that amount" meaning what you show in the examples? i haven't seen much of that either, but easily noticeable i've seen lots of. out of curiosity what primes have you used that don't show loCA?


Frankly , no primes that I can think of, there is always a chance of loCA , in my limited experience .
I've hardly ever seen it with large format lenses, but that's a different topic, I guess .

'That amount' is what I see in the examples; in the focus plane .
More on that below .

Bifurcator wrote:
I don't think it's off topic. (I think) the entire reason to have a image thread on a lens or lens group is to discuss how to use them, convert them, what their strengths and weaknesses are, and of course to brag a little. So you seem perfectly on-topic to me.




Bifurcator wrote:
And with that, I'm as confused as you are. I have a couple of hundred MF lenses and only a handful produce CA artifacts that show up in 100% screen displays.


A couple hundred ? Mate, you really like your MF lenses !
Thanks for the samples .

sebboh wrote:
i agree with you about lateral CA on in focus regions being generally not a serious problem, but loCA, or bokeh CA, or lateral color, or whatever it's called is prevalent in most of the lenses i've used. to be specific about what i'm talking about it's the purple fringing in the oof regions in front of the focus and green fringing in the oof regions behind the focus point

.....but i see it to some degree in every narrow dof shot i've taken with a lens faster than f/2 and in every narrow dof shot i've taken with a telephoto
...Show more

As for the latter part : With the Minolta MF lenses I've tried on the Nex, the difference between zoom lenses and primes I can see re. loCA is that the zooms actually do worse, but I'm assuming that's because the few I tried do worse in every respect , like resolution, flare and sharpness .

Also, the slower MF lenses don't do any better than the faster ones in my case; wide open, I'm getting PF, two stops down, it's fairly well controlled, no matter if the widest aperture is 1.7 or 5.6 .


Now here is what confuses me quite a bit: the magenta/green shift you mention, which is typical for longitudinal CA, is moved to the back with all my lenses .

See the images below :

A : focused on the hinge, PF on the focus point

B: hinge is (mis)focused to exactly the point of color shift between magenta and green fringing, which is further back

Hence, the color neutral area lies well behind the focus plane !
I can easily see the fringing change colors on the display.

I wished I could try my Minolta lenses with a different digital camera, or even another Nex .

(I hope I'm getting my terms right - foreign speaker ....)











Jul 01, 2011 at 12:42 PM
sebboh
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p.4 #7 · ROKKOR Telephoto Image Thread


Tomser wrote:
Now here is what confuses me quite a bit: the magenta/green shift you mention, which is typical for longitudinal CA, is moved to the back with all my lenses .

See the images below :

A : focused on the hinge, PF on the focus point

B: hinge is (mis)focused to exactly the point of color shift between magenta and green fringing, which is further back

Hence, the color neutral area lies well behind the focus plane !
I can easily see the fringing change colors on the display.

I wished I could try my Minolta lenses with a different digital camera, or even another
...Show more

i've seen this as well with faster lenses (not just rokkors). i believe it is a result of spherical aberration (which is common in rokkor lenses i believe) - where the focus points from different apertures are not all at the same point. theoretically this means that the transition from magenta to green occurs at a different point for the different apertures. if more of the apertures show a back focus compared to the wide open focus point the magenta/green transition should appear behind the focus point. at least that is my theory based on no credible sources.



Jul 01, 2011 at 02:58 PM
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p.4 #8 · ROKKOR Telephoto Image Thread


Yeah, I also see the green/magenta focus thing happening. This is a different thing than PF tho. It also only happens in a handful of lenses I own.

So this is kinda interesting.

Tomser sees these problems in all lenses - always or almost always.
sebboh sees them in most lenses and almost always in lenses faster than f/2.
I only see it in 10 or 20 percent of the 300 lenses I've owned in the past year and most of them are "faster than f/2".

OMG... What does it all mean? You're tearing me apart!


BTW, I should add that the green/magenta focus shift thing in my experience seems related to a lens's coating. It might be coincidence but a lens that is very well multi-coated (where many or all of the glass elements look soft rich and velvety) shows less or none compared to a lens that is single coated, uncoated, or appear whitish and hard - where the specular highlights in the lens glass are hard and very defined.


If it helps at all here's what wiki has on the topic:



    Purple fringing
    In photography, and particularly in digital photography, purple fringing is the term for an out-of-focus purple "ghost" image on a photograph. Images taken with high-contrast boundary areas involving daylight or gas discharge lamps are particularly susceptible, since chromatic aberration is worst for the shortest wavelengths that a camera is sensitive to (violet and/or ultra-violet light).

    The term purple fringe used to describe one aspect of chromatic aberration dates back to at least 1833. However, Brewster's description with a purple fringe on one edge and a green fringe on the other is a lateral chromatic aberration. A general defocus of the shortest
    ...Show more

And with that I'm kinda now also wondering about altitude. I shoot almost exclusively at or near sea-level where UV is well filtered by the atmosphere. So, how high are you guys? Also Latitude on the Earth will affect as the angular tangent of the Sun's light to the ground and through a corresponding amount of filtering atmosphere should definitely affect light color and the amount of V/UV that enters our lenses.

Thoughts?



Jul 01, 2011 at 03:18 PM
sebboh
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p.4 #9 · ROKKOR Telephoto Image Thread


bif, i don't know. processing? eyesight? camera used? most of my shooting is done near sea level as well. purple fringing (which i don't see that often) seems to be related to laCA and the magenta/green oof fringing (that i see all the time) but they're not exactly the same thing. i haven't noticed that coatings make any difference. my contax g lenses probably have the best coatings of any of my lenses (since i sold my modern autofocus lenses) and they show some of the worst magenta/green fringing (they're only f/2 as well). i attribute this to their general high contrast emphasizing the loCA, but maybe it's a zeiss design thing. i also saw it in a extremely well corrected modern lens - the olympus zuiko digital 50mm f/2 macro and have seen lots of examples not only of loCA, but also PF from $4000 modern ZM 85/2 sonnar, which i presume has the very latest T* coating.


Jul 01, 2011 at 05:12 PM
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p.4 #10 · ROKKOR Telephoto Image Thread


Ah, T* is a coating badge! Heh, I wondered WTH that meant...

And thanks for the clarification, So, you don't see PF much at all but you see the axial M/G phasing a lot. K, got it.




Jul 01, 2011 at 05:17 PM
 

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Tomser
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p.4 #11 · ROKKOR Telephoto Image Thread


sebboh wrote:
i've seen this as well with faster lenses (not just rokkors). i believe it is a result of spherical aberration (which is common in rokkor lenses i believe) - where the focus points from different apertures are not all at the same point.


Thanks, you might be up to something.
On the display of the Nex, it actually seems like that color shift is a lot closer to the color neutral area at f8, when the subject is in focus.
Hard to show in an image, though , it's more like an impression .

Not all of the lenses are Rokkors, though, and a couple of them I tried are Tokina and Vivitar zooms (100-300/5 RMC and Series 1 70-210).

Bifurcator wrote:
Yeah, I also see the green/magenta focus thing happening. This is a different thing than PF tho. It also only happens in a handful of lenses I own.

So this is kinda interesting.

Tomser sees these problems in all lenses - always or almost always.
sebboh sees them in most lenses and almost always in lenses faster than f/2.
I only see it in 10 or 20 percent of the 300 lenses I've owned in the past year and most of them are "faster than f/2".

OMG... What does it all mean? You're tearing me apart!

BTW, I should add that the green/magenta
...Show more

PF is not clearly defined - shall we just call it longitudinal CA, the usual magenta to green shift , for the sake of argument ?
'My' fringing is that way.

I'm just a tad over sea level, the lenses seem to be coated with something alright, and if one of them isn't, it won't affect all of them .

Right now, I think I will give up on the Nex with Minolta MF lenses, until they release a Nex 7 or so, and then try again .

Sometimes I'm using Mamiya RZ lenses for work, which CA like a mother, but then again they are brilliant stopped down a little, no need for wide open shooting in that case, and it's only lateral CA .

However, with a camera like the Nex, I see no point in using lenses that don't perform - for me - even halfway decently wide open .
Which is a great shame, because the Rokkors are so nice to use .

Well, maybe I get just a couple more , just for the hell of it ...




Jul 01, 2011 at 05:43 PM
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p.4 #12 · ROKKOR Telephoto Image Thread


No, I think you're right... you should give up on Rokkors and sell what you have - to me... Muahahahaaa.

But all seriousness aside that explains things a little more. I call what you're calling PF, CA... to me that's CA. PF can be caused by all sorts of things (I guess including CA too ) and it's usually without the green, yellow, or cyan components that accompany the two main types of CA. In my experience it's also almost all contained in the purple channel as ACR sees it whereas LoCA is almost all contained in the magenta channel - and sometimes partially in the red. What you showed in the building and the cars I thought looked like PF and not CA. But now that I know better K... yeah, old rokkors have some of that... CA I mean.






Jul 01, 2011 at 08:39 PM
sebboh
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p.4 #13 · ROKKOR Telephoto Image Thread


Tomser wrote:
However, with a camera like the Nex, I see no point in using lenses that don't perform - for me - even halfway decently wide open .
Which is a great shame, because the Rokkors are so nice to use .

Well, maybe I get just a couple more , just for the hell of it ...


what do like about the rokkors and what kind of lenses are you looking for?



Jul 01, 2011 at 09:04 PM
Tomser
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p.4 #14 · ROKKOR Telephoto Image Thread


sebboh wrote:
what do like about the rokkors and what kind of lenses are you looking for?


What I like a lot is the smooth manual focusing, and the solid built.
The Rokkors are also in general fairly compact .

I'm looking for long lenses, 200-500mm , which are not too heavy and large, and usable at f5.6 or so .
My two APO lenses (Minolta 100-300/100-400) fit the bill, only they don't have the built quality of the Rokkors, and manual focusing works, but is not that great .



Jul 03, 2011 at 06:20 PM
Steve Spencer
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p.4 #15 · ROKKOR Telephoto Image Thread


Tomser, why not a Minolta MC or MD 400mm f/5.6 APO? I have one and it is a fantastic lens. They are somewhat rare, but it seems to be just what you are looking for.


Jul 03, 2011 at 06:27 PM
sebboh
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p.4 #16 · ROKKOR Telephoto Image Thread


Tomser wrote:
What I like a lot is the smooth manual focusing, and the solid built.
The Rokkors are also in general fairly compact .


i thought that might be it. unfortunately for telephotos of that range good CA correction was extremely uncommon till the days of lessor build quality. the only other lenses with the build quality to match the rokkors are leica R and takumar lenses. there are quite a few good performers in from leica, but they are a fair bit more expensive (as is the rokkor 400/5.6 apo) and not particularly compact. the takumars, at least from what i've seen tend to be even worse with regard to CA. a better option might the nikkor 400/5.6 ED AIS. in general i've not been a fan of the focus rings on nikkors because of direction and excessive lightness, but i've heard that one is slower focusing. both it and the nikkor 400/5.6 ED IF AIS (faster focusing and closer focus) are supposed to be pretty well corrected for CA. a final option might be a c/y 300/4. i'm sure the build and focus would be superb, but i haven't heard anything about the lenses performance and CA correction isn't typically zeiss's biggest strength.

Edited on Jul 03, 2011 at 06:48 PM · View previous versions



Jul 03, 2011 at 06:46 PM
Tomser
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p.4 #17 · ROKKOR Telephoto Image Thread


Steve Spencer wrote:
Tomser, why not a Minolta MC or MD 400mm f/5.6 APO? I have one and it is a fantastic lens. They are somewhat rare, but it seems to be just what you are looking for.


I know, I've been looking for one of those for ages ...



Jul 03, 2011 at 06:47 PM
sebboh
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p.4 #18 · ROKKOR Telephoto Image Thread


Tomser wrote:
I know, I've been looking for one of those for ages ...


+1



Jul 03, 2011 at 07:00 PM
Tomser
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p.4 #19 · ROKKOR Telephoto Image Thread


Thanks Sebboh, will look into it !

For the record, here is one website on tele lenses for Minolta MF .

Link .



Jul 03, 2011 at 07:10 PM
LeadyGonzales
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p.4 #20 · ROKKOR Telephoto Image Thread


sorry, wrong thread


... so i add a picture:



rokkor 85mm 1.7 at 1.7 in the forrest, like it



Jul 03, 2011 at 10:33 PM
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