Fred Miranda wrote:
Still, I purchased 3 of their new ones from Amazon and two of them were short, which for my purposes was a good thing.
I have an extra 'short one' which allows for 35/1.7 + 5m infinity focusing if someone needs it.
Fred
God news! Looking at the online pictures they haven’t upgraded m to e to the new style yet, so maybe we should stock up!
I bought an OptoSigma SLB-50-5000PM for my Ultron 35/1.7. This lens is a plano convex one having a flat surface on one side and a spherical surface on the other. As the radius on the convex side is rather big, it cannot be determined by naked eye if which is side A and which is side B. I tried the reflection trick but it did not help either. I learnt from your experience that this is practically indifferent in which orientation the PCX lens is mounted. Anyway, would you have a smart idea please? THX.
Lay the filter on a flat surface like your desk put one finger one one side and one on the other . If on the curved side it will rock back and forth very slightly. If so that’s the curved side, if it don’t rock it is the flat side. Use a desk that won’t scratch the glass of course.
GMPhotography wrote:
Lay the filter on a flat surface like your desk put one finger one one side and one on the other . If on the curved side it will rock back and forth very slightly. If so that’s the curved side, if it don’t rock it is the flat side. Use a desk that won’t scratch the glass of course.
That's a good way. Alternatively just place a toothpick on top of it and you will be able to see which side is totally flat.
HaruhikoT wrote:
Given Zeiss published MTF is "A" and my simulation MTF is "B", how good Combined MTF "C"= A & B is?
I understand that is your question.
The Zeiss published MTF is calculated for a camera, that is not a Sony A7.
For a Leica M in case of the Zeiss ZM-type, I think.
This is the maximum, that can be achieved. To add is flare with a front-filter in a DIY-mount?
So .....? Optical bank measurement could give an answer. Something for the Lens Rentals team?
Jan
jankap wrote:
The Zeiss published MTF is calculated for a camera, that is not a Sony A7.
For a Leica M in case of the Zeiss ZM-type, I think.
This is the maximum, that can be achieved. To add is flare with a front-filter in a DIY-mount?
So .....? Optical bank measurement could give an answer. Something for the Lens Rentals team?
Jan
Pretty sure the Zeiss published MTF is a bench measurement from a K-8 bench device, not a camera measurement...
jankap wrote:
The Zeiss published MTF is calculated for a camera, that is not a Sony A7.
For a Leica M in case of the Zeiss ZM-type, I think.
All other ZM-lenses except Distagon T* 1.4/35 ZM are designed for film. I have not heard or read from anywhere is the measured MTF for Distagon T* 1.4/35 ZM with ot without Leica M sensor cover glass.
jankap wrote:
This is the maximum, that can be achieved.
MTF is challenging, so much depends on focus placement; e.g. you focus with zone-B (mid-zone / mid-field / whatever) instead optical center of the lens, you will most likely get overall better MTF, but center is worse. So maximum at some distance from center of image can be easily exceeded, but overall performance will be worse than with film (if we are still talking about ZM lenses, and I assume here some other lens than Distagon T* 1.4/35 ZM).
Typical to many rangefinder lens + PCX combinations is that if you correct enough for the extreme corners to be perfect then zone-B MTF from planar subject with same focus position would have lower MTF contrast %.
If I would ever need to shoot planar subjects I would use makro lens, which is optimized for the camera. In my usual photography it's usually sufficient that focus plane is "planar enough" and most importantly there is no outward field curvature. No outward field curvature is essential for avoiding stuff becoming large contrast / apparently sharp in corners, which should be blurred due to being in backboke. So someone else whom shoots planar targets with large apertures (lens tester, astrophotographer, can't figure out other use cases) cries a lot more than I do - on other hand many people wanting planar focus plane, don't care if there is outward field curvature/astigmatism in extreme corner, but for me it renders any lens to useless doorstop. So you need to know what you want and then you need to understand how you can achieve it, all photographers don't have same needs.
If maximum MTF is what you want, then Zeiss Ikon (or Leica M film) camera body with film does the trick for most ZM lenses. For Distagon T* 1.4/35 ZM Leica M digital camera body or Kolari Ultra Thin modified Sony would give maximum (or close to it) designed MTF.
jankap wrote:
To add is flare with a front-filter in a DIY-mount?
Did you buy some crappy PCX-filter without coating? I haven't had any flare issues with OptoSigma filters. I have seen more issues with adapters causing flare or Sony sensor being so reflecting causing flare, than OptoSigma filters have caused flare. Do you suffer from veiling flare or clearly identifiable reflections? Which lens and which front filter? Or is it that you did DIY the correction filter, but did not DIY suitable lens hood and compare results to lens without PCX w/ original hood?
I thought of this entry:
49-55mm step up ring
Blank 55mm filter
5m PCX bare lens (Optosigma SLB-50-5000PM)
Thin rubber gasket
55mm Retaining ring comes from disassembled Leica Elpro3 (16543) or Elpro4 (16544)
(Optional) To use original food, just add 49mm blank filter at first.
Should I cannibalize my Elpro?
Rubber gaskets?
Why does not there come somebody with a "professional" solution?
Thanks for the post.
We are on the same trail.
I have nothing against field curvature, if it is convex.
Jan
jankap wrote:
(Optional) To use original food, just add 49mm blank filter at first.
Depending on lens this may not add value from blocking light to PCX-lens, and most likely not towards the actual lens either (the stack of filters is already so thick that lens itself can't "see" the hood). I think most people were using original hoods just for mechanical protection.
jankap wrote:
Should I cannibalize my Elpro?
Depending on lens it's OK or has too small inner diameter.
I ordered lots (tens) of filters from different China eBay vendors + Amazon etc. and found few suitable sized retention rings. Method requires lots of nerves, and will result tens of 55mm filters with no use (the cheap filters have no coating and are also otherwise really low quality).
If you like to raise claims "was not as described in photos" in eBay this will give you new hobby as vendors are selling filters, which are not at all similar as in picture e.g. in picture they have retention ring on front of filter[=why your ordered one...] and in received filter it's the other type where retention ring is at back... also it may change from batch to another. The inner diameter also changes from batch to batch e.g. I got one good retention ring from Amazon basic 55mm filter -> I order 10 of them -> none of the 10 have small enough inter diameter.
So Elpro is least painful as long as your lens doesn't require larger inner diameter. And naturally can be restored if you don't no longer need the retention ring.
jankap wrote:
Rubber gaskets?
Purpose of rubber gasket in most cases is to align the PCX lens to optical center. In order to reach same purpose I cut 5-10mm pieces from thick rubber band and put 4-5 pieces around the lens. Some people spent time finding suitable size o-ring.
It's possible that somebody uses rubber gasket for something else, but I'm not aware of it.
jankap wrote:
Why does not there come somebody with a "professional" solution?
Customer base would be too small for any business. If method would have been founded when native lens selection was smaller, there would have been more customers. Not much would be needed, just few different diameter PCX-lenses, which would be thin enough to fit normal filters.
Also it would be suicide to try to sell this as "product" in modern world would, where 99% of population sees their main responsibility and life goal to moan and complain about their or someone else's (potential/theoretical) issues. Internet would cry forever as technique doesn't result perfect results with all lenses.
jankap wrote:
I have nothing against field curvature, if it is convex.
Same for me in most shooting. Of course the ideal fully planar focal plane is best, but mild inward field curvature is OK. If PCX-lens would only affect to field curvature it would be nice "adjustment method" for field curvature, but unfortunately it also has effect to astigmatism = too strong PCX = maybe nicely working inward field curvature, but there will be more astigmatism vs. "optimal" PCX.
I've found the best solution was to take the filter to an optician and get them to edge grind it to fit into a 49 mm filter ring using the same machine that they use to shape glasses lenses. I then very carefully cemented the filter into the ring using a thin smear of epoxy glue. It then functions as would any other filter, and saves a lot of hassle.
John are you able to stack a CPL in front of it using that?
I found the best solution was to have custom PCX filters made, but that might be too expensive for most folks. I had them made to 48mm, fit almost perfectly centered in front of the front element, I then used a 48mm rubber o-ring and a 49-52 step-up ring to hold it there. My lens is about 3mm longer than stock, and has a 52mm thread to match my loxias.
Here it is with just a retaining ring from a 49mm filter holding it in:
EDIT: oh and I had some in 49mm filter rings too...
Would it be physically possible for us to see a Loxia 35/1.4 with 52mm filter thread ported and optimized from the ZM 35/1.4 while having similar vignetting characteristics?
Fred Miranda wrote:
Would it be physically possible for us to see a Loxia 35/1.4 with 52mm filter thread ported and optimized from the ZM 35/1.4 while having similar vignetting characteristics?
I would buy this in a heartbeat if Zeiss managed to flatten out the field at the corners, or even reverse the direction of the field curvature, and addressed the midzone dip with the current front filter solution. Then I could finally sell all my other 35-40mm lenses.
keeerow wrote:
I was wondering if this would work for wider angle lenses such as the voightlander 15?
This technique is not dependant on focal length. However 15mm is so wide that I would assume that you would need larger diameter PCX-lens what we have been using here.
I was able to get Carl Zeiss Distagon T* 4/18 ZM to work with Hoya 58mm +1 HMC (close-up lens). I posted my experience here but the archiving has broken all the links, so I can't find it. If you can hack the archiving broken links, it originally was in this URL: https://www.fredmiranda.com/forum/topic/1453834/73#13978951. Even with 18mm I had to use file to remove parts of filter's ring to make it work:
So if you would get it optically working with close-up lens, then you would still have pretty big mechanical problem to solve...
Samuli, I read your Wiki and purchased a couple of Hoya HMC +1 lenses. I got the 52mm and 58mm varieties as I was trying them out with other lenses as well. I took both filter lenses out of the supplied rings, which was a pain as the spring loaded retention rings were impossible to grasp, so I cut them with a Dremel.
Anyway, I just laid them over the front face of the lens and held them in place with step-down rings. This is possible as the ZM18 front element isn't too big nor bulbous. Can't remember the step ring combo I used right now, and the lens is at home. Interestingly, I got better performance at the edges and corners with the 52mm lens than the 58mm lens. Not sure if it's a tolerance issue, or difference in curvature of the surfaces at the edges of the element. With the right amount of shims removed, I'm just shy of infinity at the hard stop. Can't use filters without hard vignetting, but it's a very good wide angle prime on the unmodified A7iii and the optical vignetting cleans up well enough after f/5.6.
