Samuli Vahonen
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 p.92 #16 · Front-End Filter Improves Corner Smearing | |
I see hesitation between lines you write... maybe you should try the Batis 25, it's much "easier" choise, and if you don't care about the Tamron design rendering style it may turn out great lens for you. There is no point to force yourself to buy something you don't want. Lenses will not shoot great photos, you do, but if you feel unconformatable with you lens choices it most likely will have negative effect to your creativity.
For vignetting; do you use some weird settings that Lightroom (or other similar software) automatically assigns lens correction profiles to your other lenses, but it naturally didn't for ZM25 as the software could not see from EXIF what lens it is? Also there are some correction options in camera settings. (asking these as I do not know do you have previous experience of alternative lenses - I know these questions are really stupid, maybe even offending, if you are experienced alternative lens shooter - ZM25 should not have significantly larger vignetting in A7mkII with it's backlit sensor than other 24/25mm lenses, so I'm finding your worry about vignetting weird)
hanay78 wrote:
a) I was not able to identify the bulbous side of the lens. I tried both possibilities until i found the best direction.
1500mm is really easy, I just look reflections (e.g. my roof lamp with 5 bulbs) from boths side of the lens, and it's extreme obvious which side is convex and which planar - most likely I could see it just by viewing the lens from side as 1500mm lens curvature is very visible. For 2500mm it gets much more difficult, you may be able to see it from reflections (I doubt if you didn't see it for 1500mm lens), so most likely you have to hold lens on top of something straight e.g. plastic ruler (do not use metallic, it will scratch your lens...) and observe which side of the lens sits flat on top, and which is the convex side. Also for 2500mm it's very marginal difference for the end result => I would not worry much which direction 2500mm lens "points" as in practice both directions will give almost same results. HINT: If you see difference between directions of 2500mm PCX, then either direction you didn't have lens well centered or it was tilted...
To all my OptoSigma lenses I have the employees of OptoSigma have written the focal length to side of lens e.g. "f = 4000". On all of my lenses, the bottom of this text is the planar side of the lens, and top of the text is convex side. However I do not know a) do they write it to all lenses b) do they care about the orientation when they write it.
hanay78 wrote:
b) I went to a local camera repair shop i i distroyed several old filters making trials. When you said you use a empty filter (glass removed filter), the retention ring is too high to retain the lens, located a couple of mm lower. did you put something in between or how did you did?
Well, I have purchased >35 filters to get FEW working 55mm and 52mm filters, and especially suitable size filter retention rings. I once did think that I found "the perfect 55mm UV-filter" with retention ring inner size 49.8mm. Then I ordered same filters from same seller and they were totally different. So I do not have good method finding suitable 55mm filter, which has correct size retention ring. My method was more or less "place lots of orders for different eBay vendors" for filters, which appear to look good for purpose in eBay image.
On any filter I have assempled I have never needed to "put something in between". You have found some extreme exotic filter if it's originally glass is thicker than OptoSigma lens. I have had exactly oppisite problem; there was not enough thread on some thin filters to hold the retention ring + polarizer/ND-filter on top of OptoSigma PCX-filter as it's thicker than original glass.
hanay78 wrote:
c) Elpro 3 or 4. Do dey have different diameters? 52, 55....? In case they have different sizes, are elpro 3 or 4 of the same size equal for our purposes or do they differentiate?
I do not know, but I'm sure you can find it from google - typically all this kind of info is on Leica-wiki or some other place. I would guess there is no 52mm, as most Leica R-mount lenses have 55mm, but this is just purely guessing, you better find it out yourself. On any of my lenses I do not use ElPro based filter "stack"; it's very thick and causes issues if additional filter are used (I shoot >95% of photos with polarizer).
Samuli
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and need some support.
