dumplinknet wrote:
Will this front end filter help with my lens ssue? My issue is NOT corner sharpness. In fact, it's the opposite. I, actually, GAIN sharpness in the corner while I loose boken of my pictures in wide open shots. Would this filter only exacerbate my issue?
See here:
This is taken from my thread here: https://www.fredmiranda.com/forum/topic/1430627/0#13566087
It will help and it is actually the main reason I was initially interested in these front end filter solution.
BUT you may not get the results in the end that you are hoping for.
Most fast rangefinder lenses have severe vignetting (especially compared to the DSLR counterparts)
which will also effect sharpness (more) and blur (less) towards the borders.
Furthermode with the subject (and focus) near the borders (where the field curvature has significant influence)
you may indeed end up with a little more blur towards the borders but in fact less blur in the center of the frame when having mounted such a filter.
HaruhikoT wrote: BastianK wrote:
Thanks for sharing @HaruhikoT@@@!
Interestingly the results from your copy are almost indistinguishable from the ones I get.
On my lens lower left looks significantly better than upper right as well.
Makes me frighten how similar it actually looks...
I also assumed a perfectly centered lens may not show the significant mid zone dip,
in case @Fred Miranda@@@ has a golden copy this would explain why he didn't notice it.
I found this decentering to also be apparent without filter so I send the lens in, but my hopes are not too high,
I am actually already prepared for some nonsense "within tolerances" talk.
Will have to send Zeiss some VM 35mm 1.7 samples in that case I guess...
Your mentioned "midzone dip" also appears in my copy. Compared to the center, sharpness goes lower in the area 50-80% off center, then around 90% off center, it goes higher again.
And I also see upper-right midzone is slightly worse than lower-left midzone.
I'd carefully checked my filter centering using @scrappydog@@@'s method, so perhaps my ZM35 is not a best copy...
But I have to say, even in the midzone, sharpness seems to be not worse than without PCX.
And as Guy mentioned, I also see midzone goes best at F4 or higher, whereas it is not that good without PCX below F8.
In my conclusion, there is no doubt PCX 5m improves ZM35/1.4's overall sharpness, but still have a little weakness at wider aperture.
I'm also considering to send mine to Cosina Japan(where I believe it was actually made) for inspection, but not immediately, because I need to use this lens almost every weekend
If you get good response or good fixed centering copy from Zeiss, please let me know!
Yesterday Zeiss returned the lens with proper centering (took only like 7 workdays).
Now I can back up the statement of very good across frame sharpness by f/4.0 with Optosigma 5m PCX.
Fred Miranda wrote:
The mid-field resolution drop happens with and without the front-lens and therefore it's probably a characteristic of the lens at wider apertures (f/1.4 until f/2.8)
As I just got back my ZM 35mm 1.4 I wasn't able to do an infinity comparison yet,
but at ~2.0 m focusing distance focused at the midframe (~14 mm radially from center) image quality
is simply nothing to write home about (slightly better with 5m filter though).
It takes f/2.5 for good performance here, which is in line with what you have written.
To put things into perspective in a midframe comparison to the VM 35mm 1.7:
ZM @ f/1.4 (with or without filter) is worse here than VM @ f/1.7 (with or without filter)
ZM @ f/1.8 (with filter) is still a little worse compared to the VM @ f/1.7 (with or without filter)
This is only true for the midframe, center and corners are slightly better on the ZM in the above mentioned scenarios.
At the moment I am not sure if this is something inherited in the lens design (I can't see such significant drop in image quality in the MTF)
or a filter stack issue (I don't have an M camera to check the ~14 mm region on),
what I am pretty sure about: it is not directly a field curvature issue, as refocusing should usually help with these, which it doesn't.
I might add: I have of course images to back up my statements, just lack the time to properly process all of them to show them here at the moment.
Furthermore if the weather (and day job) don't let me down I might get the chance to shoot 35mm FLE / ZM / VM / Loxia side by side, which has higher priority for me at the moment.
