JimBuchanan wrote:
I was wondering why this thread doesn't show up in the alternate gear thread, being the epitome of alternate lens use on a non-native camera body?
Very poor results from a test with a Hoya 46mm +1 diopter. Even after removing 3 shims from the rear of the lens, the focus would not reach to infinity.
Using the Optosigma 2000 lens however gives very good results. Removing 2 shims wasn't enough but with 3 shims out the focus reaches past infinity and gives a MFD of 7"! This is an unexpected bonus.
The only downside is no hard stop for infinity.
I used both a Techart and Hawk's adapter to check for infinity results on an A7Rii
With the Hawk's adapter you will be able to adjust the perfect hard infinity for the modded lens.
Regarding that 35mm + PCX 5m, orientation of the corrective lens made no visible difference in my simulated MTFs. No difference in infinity focus position, too.
Something that my simulation doesn't take into account may cause John's experimental results but I'm not sure.
Curious about how does the difference looks like. Comparison images would be appreciated.
Haruhiko
Interesting. The simulation shows no difference but John saw a difference in real tests at infinity.
Perhaps when testing the front-lens at normal and reverse orientations, alignment was not the same. If one is slightly decentered, the results may vary.
Fred Miranda wrote:
Interesting. The simulation shows no difference but John saw a difference in real tests at infinity.
Perhaps when testing the front-lens at normal and reverse orientation, alignment was not the same. If one is slightly decentered, the results will vary.
Thanks for that input HaruhikoT - its reassuring. I did say in my post on this that "I can possibly see slightly better resolution in the first set than the second", and going back to them, it's still just there. However, it was a day with quite variable lighting conditions, and that may also complicate my perception of the results. I doubt whether differences in alignment are likely to play a role, as the optometrist did such a precise job of fitting it into the filter ring that there is simply no jiggle room once its in place. Overall my sense is that a conclusion of 'no difference' is reasonable at this stage.
BTW, I made up a replacement shim today that is approximately 0.18mm thick and it gets me very, very close to infinity with the curved surface towards the lens - the results from F/2.8 on are stunning. I'll contact the NZ Zeiss agents to see if they will sell me one or more genuine article shims to get to this thickness, as I would have a bit more trust in their flatness and resulting lens alignment.
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:
That is the issue - it is field curvature. In your picture, it makes the corners look sharper. If you had taken a landscape image - focused in the center at infinity - the corners would have been blurry/smeared.
Gotcha! It's so weird because my brain thinks that this entire thread is about the opposite issue.
I understand.
Taylor Sherman wrote:
That is the issue - it is field curvature. In your picture, it makes the corners look sharper. If you had taken a landscape image - focused in the center at infinity - the corners would have been blurry/smeared.
Is this LUX M 50 ASPH right? I will post my guess about optimal front filter for this.
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:
DavidBM wrote:
Do you mean poor results *and* it won't focus to infinity, or poor results *because* it won't focus to infinity?
It's perfectly possible for the best results to come with a filter which won't focus to infinity on your adapters, depending on a combination of facts about the filter, the adapters and the tolerances of the lens.
Ideally you would test for the best results focussed as far away as you can focus, and use the filter that gives that best result, and then mess with adapters and or shims to get infinity focus.
I meant because I couldn't get the lens adjusted with adapters or internal (shim) adjustments to reach infinity. With the +1 Hoya the initial focal range was about two meters, even after removing 3 internal lens shims infinity was not reachable. In contrast, the Optosigma 2000 easily focused past infinity making this lens usable for all purposes.
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:
http://i.imgur.com/etCQMZm.jpg
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:
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 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.
FWIW, last year I shot some infinity comparisons with a friend's ZM35/1.4 and my CV35/1.7 on the M240. On the Leica, which is what I usually shoot, I felt the CV was somewhat better all-round, in respect to sharpness consistency across the frame (though I think my copy is slightly 'decentered' and the ZM may also have been). It was kind of the final nail in the coffin for what previously was residual desire to pick up a ZM35/1.4 due to the great results I had with it when I initially tested a preproduction unit way back at PPE+ in Oct. 2014. I hesitated due to its increase in price - both a higher than originally anticipated street price in the Americas ($2300 US vs. ~$1750 US in the Japanese market) and the tanking CAD. I was looking at ~$2800 CAD for the ZM vs. ~$800 CAD for the CV imported from the EU, so held out for the CV and haven't really looked back.
Anyway, I'll have to dig up the test shots but I don't recall thinking there was an obvious mid zone drop in sharpness with the ZM like I've seen with a lot of the faster Leica glass...
polylepis wrote:
I meant because I couldn't get the lens adjusted with adapters or internal (shim) adjustments to reach infinity. With the +1 Hoya the initial focal range was about two meters, even after removing 3 internal lens shims infinity was not reachable. In contrast, the Optosigma 2000 easily focused past infinity making this lens usable for all purposes.
That’s because the Optosigma 2000 is a 2m lens and the Hoya is 1m. Therefore, the Optosigma modifies to a lesser extent the focal length of the main lens.
A rough calculation :
ZM25 and Hoya +1 diopt. = 24.4mm. -> you need remove 0.6mm of shims to reach infinity
ZM25 and Optosigma 2000 = 24.7,mm.-> you need to remove only 0.3mm. of shims
That is, supposing your adapter is exactly to specifications. Are you able to focus past infinity without the front filter ?
Here shows simulated MTFs. As always please note aberrations that the master lens originally have are not included here, and this is just a simulation based on my guess value so real results may be completely different.
I expect 10m PCX may give some improvement on the 50 asph's field curvature.
The lower two graphs are Through-Focus MTFs. When field curvature is perfectly corrected all peaks in this graph should be in unison.
Upper two graphs are generally known MTFs. With the PCX contrast in 10 and 20 cycles/mm are better but 40 cyc is slightly worse at the midzone.
And I agree with Bastian, even if this PCX solution improves field curvature, there will still remain sharpened corners due to optical vignetting.
Infinity problem can also happen with this combination but 10m is extremely weak so if your adapter has just a bit (0.2mm) room to exceed infinity, you can reach infinity without removing any shims.
Fred Miranda wrote:
With the Hawk's adapter you will be able to adjust the perfect hard infinity for the modded lens.
Thank you for pointing that out! The modded lens gets a nice hard stop with adjustment on the Hawk's. Now if only there were an easy adjustment for the Techart...
artur5 wrote:
That’s because the Optosigma 2000 is a 2m lens and the Hoya is 1m. Therefore, the Optosigma modifies to a lesser extent the focal length of the main lens.
A rough calculation :
ZM25 and Hoya +1 diopt. = 24.4mm. -> you need remove 0.6mm of shims to reach infinity
ZM25 and Optosigma 2000 = 24.7,mm.-> you need to remove only 0.3mm. of shims
That is, supposing your adapter is exactly to specifications. Are you able to focus past infinity without the front filter ?
Thanks for clarifying the quantity of shim reduction required for the +1, i.e. more than the amount possible with a stock lens and adapter. Without modding the adapter, would it be possible to make the +1 work with the ZM 25 do you think?
With the stock lens and adapter, focus past infinity didn't happen. With the 3 lens shimmed removed and no front filter, the focus can go way past infinity.
polylepis wrote:
Thanks for clarifying the quantity of shim reduction required for the +1, i.e. more than the amount possible with a stock lens and adapter. Without modding the adapter, would it be possible to make the +1 work with the ZM 25 do you think?
With the stock lens and adapter, focus past infinity didn't happen. With the 3 lens shimmed removed and no front filter, the focus can go way past infinity.
It may depend on the adapter so it could be easier to find one that is a bit short than to grind it down; Guy seems to have got his ZM 25 focussing to infinity with the Hoya +1. Of course there is likely some sample variation in adapters.
DavidBM wrote:
It may depend on the adapter so it could be easier to find one that is a bit short than to grind it down; Guy seems to have got his ZM 25 focussing to infinity with the Hoya +1. Of course there is likely some sample variation in adapters.
I have no problem reaching infinity with my ZM 25, it focuses right at infinity with the Voigtlander VM-E adapter and a single bronze shim on the ZM. With the TAP it focuses past infinity with the same shim setup on the ZM.
DavidBM wrote:
It may depend on the adapter so it could be easier to find one that is a bit short than to grind it down; Guy seems to have got his ZM 25 focussing to infinity with the Hoya +1. Of course there is likely some sample variation in adapters.
Going back to Guy's post, he removed 3 shims from the front of the lens, something I did not try (oops). Still happier with Optosigma for ease of use, though the 46mm size of the Hoya allows for the OE hood placement.
polylepis wrote:
Going back to Guy's post, he removed 3 shims from the front of the lens, something I did not try (oops). Still happier with Optosigma for ease of use, though the 46mm size of the Hoya allows for the OE hood placement.
Right; but they must both give rather different correction, and only one of them will be optimal. AFAIK that's a 1 diopter strength for this lens, so it's probably worth trying to make that work at infinity.
MIRANDA1 wrote:
I have no problem reaching infinity with my ZM 25, it focuses right at infinity with the Voigtlander VM-E adapter and a single bronze shim on the ZM. With the TAP it focuses past infinity with the same shim setup on the ZM.
Your set-up is the Hoya 46mm +1 filter and the removal of a single front shim on the ZM25, correct?
