BastianK wrote:
Though I must say: I see the same loss in the midframe my Eksma Optics filter exhibits.
Still clearly apparent at f/4.0.
Check the area on the roof with the small chimney (or whatever that may be).
Agreed. I like the improvement overall, despite the softer midframe. How does the performance look comparatively to the Eksma Optics filter?
scrappydog wrote:
Agreed. I like the improvement overall, despite the softer midframe. How does the performance look comparatively to the Eksma Optics filter?
From these samples I am tempted to say exactly the same.
But my Eksma filter still is the uncoated version and struggles quite a bit with point light sources at night.
The midzone dip is absolutely horrible at all apertures. But...I only see it on the right side of the frame. There is almost no difference on the left side. Perhaps the 5m lens is not aligned in the center of the step rings.
Just a thought.
The midzone dip is absolutely horrible at all apertures. But...I only see it on the right side of the frame. There is almost no difference on the left side. Perhaps the 5m lens is not aligned in the center of the step rings.
Just a thought.
I thought the left side doesn't provide enough detail so didn't check them as carefully.
But on examining the windows closer I tend to agree.
I rechecked my samples with the Eksma and right and left side were the same.
But I will also try to improve the alining of that filter and rerun the test.
BastianK wrote:
I thought the left side doesn't provide enough detail so didn't check them as carefully.
But on examining the windows closer I tend to agree.
I rechecked my samples with the Eksma and right and left side were the same.
But I will also try to improve the alining of that filter and rerun the test.
That could make a difference. I believe it's critical to have the 5m lens well-centered.
Some possible info that may help others centre the correction lenses:
When I started putting the correction lenses inside the step up/ down rings, I used nitrile rubber o-ring material to fill the gap between the filter housings and the lens.
This helped me get the correction lenses centred as best I could.
You can get 50mm or 52mm ID nitrile o-rings for a few dollars off the web.
I have just finished reading through all the 24 pages in this thread. THANK YOU to all of you for contributing to this. Finally I can solve the FC on my Distagon 35 ZM.
Anyone know if OptoSigma has a retailer in Asia? Would be so nice to send to my family's home in Hong Kong instead of to Norway to avoid VAT.
Fred Miranda wrote:
That could make a difference. I believe it's critical to have the 5m lens well-centered.
I have now improved the construction with some tape around the lens element,
I had planned to do that with the coated Optosigma Filter anyway, but did not yet bother with the uncoated Eksma filter.
Will check if this improves the results even with this filter tomorrow.
Very nice discovery !
I'm on M43 sensors Olympus for years.
Those sensors have a lot of problems with adapted 35 film :
-heavy crop : you loose a LOT of lines, even if you get the best "center" ones
-4mm filter stack : we know since Kolarivision and LensRental article filter stack create troubles with fast/wide film lenses...and M43 ones are (sadly) the thickest ones.
So astigmatism and spherical aberrations are "enhanced" by sharpness lost (crop) and 4mm filter stack.
Can someone give me some "hints" to try a fix on an usual lens ?
My main candidates are, for now, Canon FDn 50mm f1.4 and Helios 44-2.
I really want to try this, because the only other solution i found was focal reducer (Lens turbo II for me). It works, but less than on any APS-C sensor (less crop, less filter stack...).
PhilippePASCAL wrote:
Very nice discovery !
I'm on M43 sensors Olympus for years.
Those sensors have a lot of problems with adapted 35 film :
-heavy crop : you loose a LOT of lines, even if you get the best "center" ones
-4mm filter stack : we know since Kolarivision and LensRental article filter stack create troubles with fast/wide film lenses...and M43 ones are (sadly) the thickest ones.
So astigmatism and spherical aberrations are "enhanced" by sharpness lost (crop) and 4mm filter stack.
Can someone give me some "hints" to try a fix on an usual lens ?
My main candidates are, for now, Canon FDn 50mm f1.4 and Helios 44-2.
I really want to try this, because the only other solution i found was focal reducer (Lens turbo II for me). It works, but less than on any APS-C sensor (less crop, less filter stack...).
Thank you for the comment!
I did some simulation considering 50mm lens + M43 sensor (4mm filter stack), but unfortunately couldn't find optimal PCX for this combination
Your concern is true. In the simulation, I also see some astigmatism and spherical aberrations caused by the 4mm filter stack.
Then I simulated 1~10m PCX put in front of the 50mm lens. Astigmatism is improved but field curvature and spherical aberration get worse by those PCX. Overall IQ (MTF) is not improved by any of those PCX at least in theory.
BastianK wrote:
I have now improved the construction with some tape around the lens element,
I had planned to do that with the coated Optosigma Filter anyway, but did not yet bother with the uncoated Eksma filter.
Will check if this improves the results even with this filter tomorrow.
My temporary (and potentially permanent) solution is that I took a 3mm wide rubber band (about 1mm thick), and snipped four 2mm x 2mm squares, which I then inserted on the side of the lens in a North, South, East, West configuration. I used little flat head screwdrivers (from an eyeglass repair kit) to wedge them in on the sides of the lens. Because the little rubber squares are made of rubber, they compress, making it easy to fit squeeze in on the sides of the glass. They basically act as compressible shims. I haven't tested the lens with this fix yet.
scrappydog wrote:
My temporary (and potentially permanent) solution is that I took a 3mm wide rubber band (about 1mm thick), and snipped four 2mm x 2mm squares, which I then inserted on the side of the lens in a North, South, East, West configuration. I used little flat head screwdrivers (from an eyeglass repair kit) to wedge them in on the sides of the lens. Because the little rubber squares are made of rubber, they compress, making it easy to fit squeeze in on the sides of the glass. They basically act as compressible shims. I haven't tested the lens with this fix yet....Show more →
I couldn't either, because of snowfall "infinity" was not visible.
@HaruhikoT
That's what i was expecting...sadly
Thanks !
I think i will go the Sony A3000 way, for film lenses : E mount, 20MP APS-C and 0.6 mm filter stack only
Combined with a Lens Turbo II, it is going to be cheap AND corrected enough.
Until someone can tell me to another E mount/thin filter stack combination
PhilippePASCAL wrote:
Very nice discovery !
I'm on M43 sensors Olympus for years.
Those sensors have a lot of problems with adapted 35 film :
So true. This is precisely why I basically gave up on adapted glass on my μ43. It's an unfortunate state...though Olympus & Panasonic never have a problem with sensor dust either...
Yes, no difference with Eksma filter, still significant midzone dip.
Performance is also (still) very symmetrical.
I will once more try it reversed, but don't expect different results.
Will wait for Optosigma filter.
My significant other did me a favor and tested my Zeiss 35/1.4 ZM + OptoSigma filter for me while I was at work. I fixed the centering of the filter by fitting four small pieces of rubberband in between the lens and the step-up/step-down filter stack in a North, South, East, West configuration.
I uploaded the images to my Flickr account at full resolution. You can download all of the shots from Flickr. Link: https://flic.kr/s/aHskQd6cew
I also included a shot of how I centered the lens.
scrappydog wrote:
My significant other did me a favor and tested my Zeiss 35/1.4 ZM + OptoSigma filter for me while I was at work. I fixed the centering of the filter by fitting four small pieces of rubberband in between the lens and the step-up/step-down filter stack in a North, South, East, West configuration.
I uploaded the images to my Flickr account at full resolution. You can download all of the shots from Flickr. Link: https://flic.kr/s/aHskQd6cew
I also included a shot of how I centered the lens.
