zaphodm, can you clarify how this clip on filter and front-end filter are supposed to be relevant? (honest question I do not understand)
Why I'm asking this - there are two issues caused by large ray angle:
1. image "smearing" which get stronger in relation to ray angle - 1b) but fast lenses can project rays to center in too deep angle so center of image can be also have decreased image quality
2. CFA (Color Filter Array) and microlenses do not work in large angle, causing color shifts and additional vignetting
Item #1 can be fixed by technique discussed in this thread OR by modifying camera sensor cover glass to be thinner (there is other thread for that). #1b can be only fixed by modifying camera cover glass, not by front filter methodology.
Item #2 can be fixed by using backlit CMOS (=A7r mkII), which is able to use larger ray angle OR by using post processing e.g. Lightroom Flat Field plugin.
You seem to ask from here because of item #2 (or then something completely irrelevant), which this thread technique does not have any effect.
Only relation I see is that adding these clip-on filter add additional glass in optical path is similar as the artificially thick sensor cover glass in A7-series cameras. Smearing caused by additional glass between lens and sensor could be fixed by front-end filter technique - not color issues. Also adding additional glass between lens and sensor will not cause color shifts, unless the filter is doing some filtering of light, when there will be shift because at center the light goes through "shorter distance" through the filtering glass element compared to edges of image - but this has no relation to front-filter technique as it can't fix color shifts.
I do not understand why someone would artificially want to cause issues by using these clip-on filters.
Samuli Vahonen wrote:
zaphodm, can you clarify how this clip on filter and front-end filter are supposed to be relevant? (honest question I do not understand)
I guess that's why I was asking the question.
Why I'm asking this - there are two issues caused by large ray angle:
1. image "smearing" which get stronger in relation to ray angle - 1b) but fast lenses can project rays to center in too deep angle so center of image can be also have decreased image quality
2. CFA (Color Filter Array) and microlenses do not work in large angle, causing color shifts and additional vignetting
Yep. I get that. The reason I was asking was that they seem to often occur together, and both seem to be caused by the steep ray angles. I guess I was wondering if the filters somehow *reduced* the resultant ray angle between the filter and the sensor and that was how it was reducing colour shifts. Was wondering, if that was what was actually happening, if that would also reduce smearing.
The reason I asked is precisely because I *don't* know if it is relevant and there are far smarter people than me in this thread with knowledge on the issues.
zaphodm wrote:
I guess I was wondering if the filters somehow *reduced* the resultant ray angle between the filter and the sensor and that was how it was reducing colour shifts.
OK I think I got it now why you are asking. If both sides of this clip on filter are planar and filter material is homegenous, then it can't change ray angle in meaningful amounts. What it will do under these conditions, is that different wavelegths will hit slightly different point on sensor (=color errors on contrast edges).
I still don't understand why anyone would like to use this kind of clip-on filter as it can only cause negative effects, unless one uses lens which is specially designed taking into account clip-on filter and sensor cover glass caused issues.
I still don't understand why anyone would like to use this kind of clip-on filter as it can only cause negative effects, unless one uses lens which is specially designed taking into account clip-on filter and sensor cover glass caused issues.
Fair point, but also what many would say to adding extra elements in front of lenses before seeing the results in this thread.
I always want to add: Thank you for your genuine engagement with my question! It's a feature of the forums on Fred's site, and something that wouldn't happen on many others.
It is just a matter of time before we see clip correctors for Leica M lenses. It took several years for the flat clip filters to appear.
Given that the E mount registry allows for M mount lens use, the clip correctors will appear sooner than later.
I thought your question was right on the money.
zaphodm wrote:
Fair point, but also what many would say to adding extra elements in front of lenses before seeing the results in this thread.
I always want to add: Thank you for your genuine engagement with my question! It's a feature of the forums on Fred's site, and something that wouldn't happen on many others.
Mathieu18 wrote:
Has anyone tried a front filter on the Contax G 35/2? Would the same 1500mm PCX work?
i think 5m or 4m would be optimal, but i forget. improvement won't be huge though because the g35 isn't as strong a lens to begin with and it doesn't smear that much either.
Mathieu18 wrote:
Has anyone tried a front filter on the Contax G 35/2? Would the same 1500mm PCX work?
According to table in my wiki this was page 4, #16 = 5000mm/6000mm - on my real life testing it was obvious that 4000mm is optimal for boke shooting, 5000mm did leave too much field curvature (or there is outward field curvature on design of the lens).
I do not like this lens, I tried my best to like it and get good results but boke remains crappy, some images and my thoughts in FE megathread, page 2234, #1.
Thanks, think I'll just ignore it. I had one a while back before the front filter solution was found. Seemed to suffer from massive field curvature especially at closer focus distances. Sounds like I'll just ignore it, the 28 is pretty remarkable as well with the filter so I'm happy.
Appreciate the feedback.
sebboh wrote:
i think 5m or 4m would be optimal, but i forget. improvement won't be huge though because the g35 isn't as strong a lens to begin with and it doesn't smear that much either.
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Samuli Vahonen wrote:
According to table in my wiki this was page 4, #16 = 5000mm/6000mm - on my real life testing it was obvious that 4000mm is optimal for boke shooting, 5000mm did leave too much field curvature (or there is outward field curvature on design of the lens).
I do not like this lens, I tried my best to like it and get good results but boke remains crappy, some images and my thoughts in FE megathread, page 2234, #1.
I bought a 5cm planoconvex for my CV 35mm f1.4 and A7ii body. The results are much better, with increased corner performance, way less field curvature and even slightly better sharpness in the center.
I've seen the video showing how to remove shims so I can focus to infinity but it seems like I can't do this without specialized tools. I've also called almost all the camera shops in SF to see if I can get help with it and no one says they will.
IMO it seems like I need to buy some tools to do it myself. In the beginning of the video, there is a grippy spongy appliance that is applied to the front of the class that is able to be pressed onto the class in order to remove it the element. Then there is a tool that looks like A cross between tweezers and chopsticks that unscrew the shims out. What are the names of these two tools? Does anyone own and perhaps could let me borrow them for a few days? I'm happy to pay shipping both ways.
raydeng wrote:
IMO it seems like I need to buy some tools to do it myself. In the beginning of the video, there is a grippy spongy appliance that is applied to the front of the class that is able to be pressed onto the class in order to remove it the element. Then there is a tool that looks like A cross between tweezers and chopsticks that unscrew the shims out. What are the names of these two tools? Does anyone own and perhaps could let me borrow them for a few days? I'm happy to pay shipping both ways.
Suggest you have a look at Japan Hobby Tool catalog - http://japanhobbytool.com/catalog-e.pdf
page 10.
Sure there are other tools sellers in ebay or amazon or where else, I found Japan Hobby Tool to be reasonably priced and they got most of the stuff available from one place without needing me to get things from different vendors thus saving shipping costs.
P.S. I'm surprised your local camera repair shops can't help. Those tools are their bread n butter tools...
raydeng wrote:
I bought a 5cm planoconvex for my CV 35mm f1.4 and A7ii body. The results are much better, with increased corner performance, way less field curvature and even slightly better sharpness in the center.
I've seen the video showing how to remove shims so I can focus to infinity but it seems like I can't do this without specialized tools. I've also called almost all the camera shops in SF to see if I can get help with it and no one says they will.
IMO it seems like I need to buy some tools to do it myself. In the beginning of the video, there is a grippy spongy appliance that is applied to the front of the class that is able to be pressed onto the class in order to remove it the element. Then there is a tool that looks like A cross between tweezers and chopsticks that unscrew the shims out. What are the names of these two tools? Does anyone own and perhaps could let me borrow them for a few days? I'm happy to pay shipping both ways. ...Show more →
Would be great if you could share some with/without filter comparisons with that CV 35mm 1.4 lens, I think there hasn't been one yet
Random question, I replaced my Contax G Adapter, and the new one doesn't seem to focus to infinity anymore with the front filter on the G28. If I manually wind the lens, I can see it has more focus play to probably reach infinity, but i cant get the Techart there, even in MF mode... Anyone come across this?
I'm having the same problem here. Oddly, if I manually wind the G28 all the way in, mount it and manually focus, I'm past infinity and can hit infinity. As soon as it focuses to a close distance and back towards infinity I'm SOL. It's a software issue with the TA-GA3, for some reason it stops adjusting the focus of the 28 long before it hits a hard stop... There's an AF adjust procedure but A) I cant get it to work and B) remains to be seen if it would just de-calibrate AF or actually fix the problem.
OpticalFlow wrote:
So meanwhile I received a new (used) lens body for my Contax G 28. This one is not defective (no wobble) and after removing a shim I still can't quite focus to infinity with the Techart GA3 adapter when the PCX 1.5m lens is in place - despite being able to focus quite a bit past infinity without the filter.
However, when mounting the lens on my cheapo manual adapter I can focus past infinity even with the filter on it. I can tell just from looking at the lens that the manual adapter brings the optical group much closer to the film plane than the Techart.
In practical shooting I found that the AF of the Techart GA-3 which appears to do a reasonable job in indoor and urban situation often fails for the G 28 in outdoor settings (with lots of fine texture and contrast). Therefore the G28 will probably simply stay on the manual adapter. I'm very pleased with the results. ...Show more →
Actually I'm thinking of applying some sugru into the Contax GG1 hood to fix the Optosigma, instead of getting stepup/step-down filters...Would there be problems?
kaioyang wrote:
Actually I'm thinking of applying some sugru into the Contax GG1 hood to fix the Optosigma, instead of getting stepup/step-down filters...Would there be problems?
I'm having the devil of a time with the rubber band centering method so I've ordered some Sugru and will see how that works.
