Fred Miranda Offline Admin Upload & Sell: On
|
artur5 wrote:
Are we assuming that a 5m. PCX is the best for the CV 35/1.7 ?. If so, in what grounds?. AFAIK, nobody has tried a different PCX with this lens and HaruhikoH didn’t make a simulation either.
For what is worth, the Biogons G21 and G 28 both work best with a 1.5m. PCX filter. Also, if memory serves me right, the ZM25 optimal filter was 2.5m. or maybe 3m?... All these three lenses are Biogons, hence quite symmetrical but there’s no direct correlation between focal length and best PCX for each of them. It depends mostly on the design. The fact that 5m. works fine with the Distagon ZM 35/1.4 says nothing about the Ultron 35/1.7. Probably this lens would perform better with another PCX. In fact, for what I’ve seen in that test of some pages ago, 5m. seems too weak.
It’s a pity that those filters aren’t neither cheap nor easy to purchase, otherwise nothing easier than buy half a dozen of different focal lengths from 1m. to 5m. and find the best suited for every lens.
BTW Fred, I hope that the people living in those "slanted houses" of your tests, know nothing about this forum, or I'm afraid that you'd end up being sued for invasion of privacy or something .....Show more →
I will definite get sued by those homeowners! It's just so easy and fast for me to test from my backyard.
Regarding your question about the optimum PCX for the CV 35/1.7 Ultron... @BastianK and @Phillip Reeve tested this with a 5m with great results. I wanted to find out if this was the optimum PCX as well and asked @HaruhikoT to run a simulation on it based on images from the lens itself.
Here is what he just wrote me:
______________
Hi Fred,
Thanks for sending these images.
Short answer: 5m PCX is optimal for the CV.
Detail description:
From your images I've successfully got its CRA(chief ray angle).
CV's estimated CRA is 30.6deg, while ZM has 28.1deg.
That means CV's ray towards sensor is a bit steeper than ZM.
Simulation results are little bit confusing.
Below image I also add graphs of ZM at the same aperture F1.7 for comparison.
With PCX 5m mid zone dip can be seen in both CV and ZM,
this is not consistent with Bastian and Guy's test results, but I don't know why .
PCX 4m behinds 5m at any point.
PCX 7.5m may little bit better in midzone but corner gets worse.
* Recently I found a PCX manufacturer provide this focal length that's why I add 7.5m this time...
_________________
|