Every time we add a glass element to our lenses, we can expect a slight loss in contrast. This loss may be almost imperceptible though, especially if the lens has already superb contrast. I beat it would show up on the MTF graph if tested properly. I'd say nothing to worry about..
GMPhotography wrote:
David I'm losing nothing on center at all with the PCX 2500 and the 25 but gaining a load in the corners. Basically what these PCX lenses are doing is essentially flatening out the field curvature . Optically that is.
Absolutely, Guy. But I think what is happening on your great 25 is that the PCX2500 is flattening the *induced* field curvature - the curvature due to the Sony filter stack. I don't think it's affecting the native field curvature (of which there is in fact very little on the 25). That's why the PCX is so much better a solution to induced field curvature than focussing in the midfield or some other focus based solution, which does involve tradeoffs.
The 28 though likely has a lot of *native* field curvature (either that or it doesn't resolve well in the periphery - the MTF says one of those must be true). A PCX chosen based on simulations may get rid of the *induced* field curvature, but the best case is that it will leave the *native* field curvature completely unchanged.
That's why I was excitedly speculating that there might be a way of doing a different kind of simulation to tell us how to get rid of native FC by adding an element. But that would be much more complicated, it would involve basically running the simulation software in full lens design mode, because you wouldn't be starting with a theoretically perfect lens, but rather with the original MTF.
Fred Miranda wrote:
Every time we add a glass element to our lenses, we can expect a slight loss in contrast. This loss may be almost imperceptible though, especially if the lens has already superb contrast. I beat it would show up on the MTF graph if tested properly. I'd say nothing to worry about..
Yep. After all, with modern coatings there are some pretty impressively contrasty lenses with tons of elements (though I guess some of this is down to ray-tracing of non image-forming light paths, which is above our pay grade when doing simulations to choose front filters)
Someone ought to create a "PCX bank" from where we could borrow and try different filters until finding the best one for each RF lens.
Jesting of course, but maybe isn't such a bad idea ?
A more difficult question!
You're likely right about the date; I think I remembered the 2012 date from Bastian's review, but I'm not sure. And the old one was certainly discontinued in 2008...
Fred Miranda wrote:
I meant which PCX!
I think the latest CV 28/2 was released in 2008 but could be wrong.
Fred Miranda wrote:
I think there are a couple of 28mm Leicas with 10-blade apertures.
Those are out of my price league
The ZM25 isn't though, it is surprisingly affordable used so I am tempted.
A more difficult question!
You're likely right about the date; I think I remembered the 2012 date from Bastian's review, but I'm not sure. And the old one was certainly discontinued in 2008...
According to Cameraquest the 28/2 M version was announced in 2008
GMPhotography wrote:
With the PCX2500 it's really nice and small to
The size would be a nice bonus. What is most important to me is good flare resistance and nice sun stars. I am not too concerned about sharpness which is good enough for me in late 70's lenses.
Ideally I would like to have a 20mm lens to go with my CV35 but there is no option which is affordable enough (<600€, front filters included) for me. So the ZM25 seems to be the most attractive alternative.
Right now my kit is CV12, Tokina Firin 20mm, ZM25,35,85 and I just added a Rokinon 135. I can do night skies with the Firin. Coma is low, sunstars Zm25,35,85 and CV 12. I want really sharp and wide the Firin looks to be it. Like having these options . Very light weight kit outside the 135.
Fred Miranda wrote:
Good point on the inability to modify infinity distance. How are folks using the CV 35/1.7 with PCX lenses if infinity tweaking is not possible?
Cheap, too short adapters
Supposing a PCX5000 is used with the CV35, an adapter 0.25-0.3mm. too short would do. I don't know if the Hawks has that much for infinity adjust. Anyway, my cheapie Pixco focused already past infinity with normal lenses when I purchased it and now, after tiresome shaving sessions, is only 9.35mm.
BTW I read often that the registry distance of the Leica M mount is 27.80mm.
According to this, adapters for Sony-E should be 27.80 -18 = 9.80mm.thick.
In my experience, an adapter measuring exactly this won't reach infinity with a normal M lens.
For what I gathered, 27.80mm refers to the distance from lens flange to the back pressure plate of film cameras. Now, we must take into account that film supports have a thickness between 0.13-0.15mm and the emulsion, which is many times thinner than the plastic support, is on the outer part, facing the lens So, the real distance from flange to focal plane (film emulsion or sensor ) isn't exactly 27.80, but 27.80 minus film thickness. Let's say 0.14mm. That makes it 27.66mm or, to practical purposes, something between 27.64 and 27.68mm. depending on tolerances of camera and lens
If you own a caliper precise up to 1/100 of mm. take time to check your adapters and see if you can reach infinity with those that are equal or more than 9.80mm.thick. My five cents bet is that you won't.
Arthur I gave up on all fixed adapters. Heck you can buy them all from me there on the board. I bought another Hawks for the ZM 25. What's nice about them is you can adjust infinity and you do get some play. On a CV 35 I used a Hawks but I was not using a PCX either but I did have room to go past normal infinity
