p.4 #3 · NEX with Contax G after 28/2.8: 45/2 or 90/2.8?
JimBuchanan wrote:
From my limited knowledge of reading MTF charts, I believe the Contax G lenses to have higher microcontrast versus the ZM version out to 14-16mm image height, working well with the 1.5x sensor. http://farm7.staticflickr.com/6005/5992317024_4ebcf621c2_z.jpg
But the ZM is sharper WO? I'm not good at reading these things
p.4 #4 · NEX with Contax G after 28/2.8: 45/2 or 90/2.8?
frezeiss wrote:
But the ZM is sharper WO? I'm not good at reading these things
no, the bottom set of lines are the ones that come closest to describing sharpness (they describe contrast in high frequency details). the upper set of lines where the zm performs better is contrast at lower spatial frequencies.
p.4 #5 · NEX with Contax G after 28/2.8: 45/2 or 90/2.8?
sebboh wrote:
no, the bottom set of lines are the ones that come closest to describing sharpness (they describe contrast in high frequency details). the upper set of lines where the zm performs better is contrast at lower spatial frequencies.
Any chance someone could give a walkthrough of what we're looking at here? Ok, left is F/2 and right is F/4. The bottom set of lines "best describes sharpness" where higher is better. What's with the other two and the dotted part of the lines for instance? The further right you go - the closer to the edge of an image? Things like that.
And is there a source for these charts where I could look up and compare various lenses?
p.4 #6 · NEX with Contax G after 28/2.8: 45/2 or 90/2.8?
uhoh7 wrote:
My mainstay at 90 has been the tele-elmarit---the little one.
I'm very curious as to how the contax 90 compares to the leica. I've got a nice tokina 90 as well, but it's too heavy for the field.
I hear some mixed reports on the contax--but that may just be copies.
tele-elmarit 90
Rock Huffwell is sure the contax is sharper, but he also loves the 21
I have probably posted these before (sry), it's a shot from a couple of weeks ago. The G90 is mighty sharp, first full image then a 100% crop. Probably F/4.
p.4 #7 · NEX with Contax G after 28/2.8: 45/2 or 90/2.8?
wfrank wrote:
Any chance someone could give a walkthrough of what we're looking at here? Ok, left is F/2 and right is F/4. The bottom set of lines "best describes sharpness" where higher is better. What's with the other two and the dotted part of the lines for instance? The further right you go - the closer to the edge of an image? Things like that.
And is there a source for these charts where I could look up and compare various lenses?
thanks for any enlightenment!
-- Wilhelm
Someone else can probably explain better, so I'll take a shot to see how far off I am
They're standard MTF charts, well not totally standard since two lenses are plotted on each. The vertical axis is the % of contrast resolved (1.0 being 100%), the horizontal is distance from the lens axis (0 being at the center of the lens). The graphs represent the resolution of the lens at the various LPmm's (frequencies), the top set being 10 LPmm. As you progress from the center of the frame outward (notice some falloff in sharpness near the outsides?). Flatter = better across the frame.
Someone (Denoir I believe) recently posted a good visual description of microcontrast as a function of contrast plotted vs. frequency. I don't have a link to the thread but if I come across it, or someone else knows it we can add the link.
I have heard people say that 10 LPmm tells you about the contrast and 40 LPmm tells about resolving power, but I think to get a good idea of the level of detail resolved everything needs to be considered as a whole, hence the microcontrast thing.
p.4 #8 · NEX with Contax G after 28/2.8: 45/2 or 90/2.8?
Well, after reading this thread I have agreed to buy a 90 this evening!
What are people's experience with adapters? I would prefer to buy budget if they have been found to do the job. Will only be used on my NEX5N.
Incidentally, somebody is selling a 90 that he claims has been converted to EF. I thought this was impossible given the registration differences?
p.4 #9 · NEX with Contax G after 28/2.8: 45/2 or 90/2.8?
lenticular11 wrote:
Well, after reading this thread I hav agreed to buy a 90 this evening!
What are people's experience with adapters? I would prefer to buy budget if they have been found to do the job. Will only be used on my NEX5N.
Incidentally, somebody is selling a 90 that he clims has been converted to EF. I thought this was impossible given the registration differences?
Never seen that. Not particular good-looking (as opposed to the original) but I guess the glass is the point, not the looks :-)
Jacob D, thanks for the link and explanation. From what I understand at best one can read out some key behaviour (ie contrast/sharpness) and compare within the same brand. But going over to another brand it seem hard to compare.
