Fred Miranda wrote: DavidBM wrote: Fred Miranda wrote:
Without any front-end filter on a stock A7RII, the ZM 28/2.8 is acceptable at f/10 across the field (infinity)
The extreme edges are good but not great at this aperture. I am hoping that adding a 1.5 PCX filter will improve this performance.
Here are some crops without the front-end filter. (I will only receive the filter on Jan 10th for a comparison)
Interesting!
I started by comparing the 28mm ZM MTF with the Loxia 2/35 to get a sense of how they compare, and whether if the 28 ZM can be got to near native performance on the Sony with the aid of front end filters, it would be competitive.
So the published MTFs have the ZM 28 not quite a s good as the Loxia 35; actually notably worse in the midfield, similar in the centre and corners, where there is a quite bit of (probable) astigmatism in both.
But then I thought I should have a look at the ZM 2/35 biogon on which the Lox is based. VERY interesting. The Loxia, as we have seen, is much better than the 2/35 when used on a Sony. But the 2/35 ZM Biogon has a noticeably nicer MTF than the Loxia (assuming their intended cover glasses, obviously). So whatever tweaks were done to the Biogon to turn it into a Loxia Biogon still leave some unresolved astigmatism (that the ZM doesn't really have). The ZM 2/35 is way ahead of the ZM 2.8/28
This makes me a little pessimistic about a front filter on the 28; that solution (especially since it'll be a stock filter and not one calculated to purpose) may improve it's performance on Sony quite a bit, but it seems reasonably to assume that it won't provide nearly the improvement that the recalculations that made the Loxia provided — which as we have seen are only partial. In which case we can expect that a front filter corrected ZM28 will be at least as bad, and probably more, relative to a native 2.8/28 ZM as the Loxia is to the native ZM35
If all that's the case (many assumptions, I know) then I doubt if a corrected 2.8/28 ZM would be really desirable. The lens is starting off worse than the Loxia native - for -native, and it's even corrected on Sony it will be even worse still than the Loxia.
Of course this might all be wrong: I look forward to tests. Also even if I'm right, the correction might make a lot of sense for someone who already owns one.
Makes sense David. Still, I'm stubborn and want to see real world tests with these filters.
I will throw in the Zeiss 28/2 ZF into the mix when comparing the ZM with filter and no filter.
There is no perfect 28mm prime for the A7RII and any solution has to blow away what I get with my 16-35/4@ 28mm, which is flat-field and actually very good at f/6.3 across the field. I'm hoping the ZM 28/2.8 will be at least a little better with more micro-contrast for a very small 28mm prime alternative.
Hi Fred,
The Leica R 28mm f2.8 Elmarit V2 may be about the best 28mm lens to get sharp into the corners of an A7r or an A7rII. I am keeping mine.
Below are 2 images taken the lens set to f16, not to get the focus into the corners but to hold focus to the rear of the images. Even getting into diffraction the lens holds up well.
