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Goyo 0.95 C-mount lens image circle

Discussion in 'Adapted Lenses' started by burdickjp, Jun 1, 2013.

  1. burdickjp

    burdickjp Mu-43 Veteran

    235
    Feb 25, 2013
    I've been looking for a good and inexpensive 25mm lens to use as a daily-driver on my E-P2. All of my current lenses are for the M42 mount. My 25mm lenses are a Vivitar pyramid, which is too large for putting my camera in a cargo pocket, and a Soligor which is hazy. I've looked into native options, and am now looking at c-mount lenses.

    According to this fancy-pants spreadsheet a 21mm image circle would be necessary to cover a 4/3 sensor. If I'm understanding this right, it makes sense, as that is, by definition, what 4/3 means.

    It has been discussed that the infamous Noktor lenses are Goyo 0.95 lenses with fancy mounts. According to Goyo's spec sheet, their 0.95 lens has a 1" image circle which would make it a 17mm diameter according to wikipedia and that fancy spreadsheet says it wouldn't work.

    So...is Noktor doing anything else fancy to make that work? Are there any other, similar 25mm lenses which would make me happy? It looks like Goyo has some 4/3 lenses, but only go down to f2. That is faster than either of the lenses I currently have, though.
     
  2. shutterduster

    shutterduster Mu-43 Regular

    144
    Feb 8, 2013
    Keremeos, BC. Canada
    Dave T
    The actual conversion is 1" equals 25.4mm so it should work fine.:thumbup:
     
  3. burdickjp

    burdickjp Mu-43 Veteran

    235
    Feb 25, 2013
    The current definition of an inch is 25.4mm, so it's not just a conversion, it's the law! Odd, isn't it?

    Either way, if we're talking a 25.4mm image circle, then why do most 1" cine lenses leave vignetting when adapted to micro four-thirds cameras? I'm thinking there's something more there. That spreadsheet does a nice job of illustrating image circles and sensor sizes.
     
  4. RobWatson

    RobWatson Mu-43 Hall of Famer

    Sorry, not true. 1" vidicon tubes are the reference and they are effectively 16mm diameter so 1" format actually means 16mm diameter image circle.

    While it certainly is true than 1" = 25.4 mm sadly 1" optical format = 16 mm image circle. Pretty annoying.
     
  5. burdickjp

    burdickjp Mu-43 Veteran

    235
    Feb 25, 2013
    Anyone in the Chicagoland area want to get a hold of Midwest Optical and see if they'll let you mount a few lenses and shoot a few pictures? It'd be worth it just to look at their 4/3" range. I would, but I'm stuck in Carbondale for the next month or so.

    It still appears Noktors are optically unmodified Goyo 0.95 lenses, which has me wondering if the image circle is large enough to cover a micro four thirds sensor. Maybe they are doing similar modifications that ekoe camera is doing on Fujinon TV lenses?
    To that end I emailed ekoe camera and asked about Goyos.
     
  6. RobWatson

    RobWatson Mu-43 Hall of Famer

    I have a gallery of images taken with E-P1+Navitar 25mm F0.95 lens that is 1" format - towards the end most of the photos are uncropped so you can see what to expect.
     
  7. madogvelkor

    madogvelkor Mu-43 Top Veteran

    937
    Feb 22, 2013
    Connecticut
    Yeah, that is one of the confusing things with inch based sensors, they don't refer to the actual physical size of the sensor. I believe 4/3 is the equivalent of a 1.3" tube, which is why a 1" sensor won't cover them.

    Some lenses are made with an overly large image circle though, designed with the idea that only the sharp center would fall on the sensor. So you do get C mount lenses that will cover the 4/3 sensor, but you get softness and distortion on the edges.
     
  8. burdickjp

    burdickjp Mu-43 Veteran

    235
    Feb 25, 2013
    I'm expecting that may be the case with the Goyo lenses, since they have previously been adapted to micro four-thirds. I'm just curious what may have been done to make them work.
     
  9. Artorius

    Artorius Mu-43 Regular

    The SLR Magic Hyperprimes? If that's what you are referring to, they are definitely totally different lenses. I don't know why people keep insisting they're rehoused lenses.
     
  10. burdickjp

    burdickjp Mu-43 Veteran

    235
    Feb 25, 2013
    Apparently it used to say on their website that the lenses were manufactured by Goyo. Some have claimed the pre-production Noktors very much resembled Goyo's c-mount lenses.
     
  11. burdickjp

    burdickjp Mu-43 Veteran

    235
    Feb 25, 2013
    I'm going to be stopping by Midwest Optics sometime soon to take a look at their c-mount things. Apparently one of their managers is familiar with our endeavors and wants to talk to me when I stop by. I'm hoping to go through as many of their lenses as I can and put together a review. Exciting!

    Unfortunately, I'm tied for the next month or so, but I will report back as soon as I can.
     
  12. speedandstyle

    speedandstyle Mu-43 Hall of Famer

    It is true that Goyo does the manufacturing for the SLR Magic hyperprime lenses. Just like numerous companies made lenses for Vivitar back in the day. SLR Magic designs the lenses and then contracts Goyo to do the actual work. This is a very very old norm in all genres of manufacturing.

    Correct! The old video sensor sizing system was based on the diameter of the tubes not on the image size. The image size is about 2/3 the size of the diameter. The same goes for a 1/2 inch or 2/3 inch video sensors.

    Here is a picture of a tube, taken from wikipedia.
    400px-Vidicon.
     
  13. burdickjp

    burdickjp Mu-43 Veteran

    235
    Feb 25, 2013
    The important thing to note here is that it's very unlikely SLR Magic 'designed' anything about these lenses. The engineering involved in lens design is overwhelmingly complicated and expensive.

    The most likely case is that they used preexisting Goyo lenses.
    The second most likely case is that Goyo marginally changed a preexisting lens design for SLR Magic.
    Evidence supporting either of those hypotheses is that the early lenses, and promotional material from SLR Magic shows lenses which very much resemble Goyo off-the-shelf lenses.


    Less likely than that is that these are some kind of bespoke design done by Goyo for SLR Magic.
    The least likely case would be SLR Magic designing anything.
     
  14. Artorius

    Artorius Mu-43 Regular

    Why is it so hard to believe? Look at the specs on the lenses. Also note that the lenses cover the 4/3 sensor which most c-mounts as wide as the SLR Magic 12mm don't. Also, just look at the reviews of the lenses! These are high quality optics and definitely not old designs. The glass is different, the appearance of the lenses is different, the iris is different. Just look and compare. I don't understand why its so hard to believe SLR Magic designed these lenses. They purchased a license to use the Noktor name just so they could show people like you they're getting serious about they're optics.
     
  15. RobWatson

    RobWatson Mu-43 Hall of Famer

    Designing lenses is not so hard. Getting someone to make glass to exacting specifications is quite a bit harder.
     
  16. speedandstyle

    speedandstyle Mu-43 Hall of Famer

    Some may not know the Noktor/SLR Magic story. They started out as two totally separate companies. SLR Magic started off simply taking c-mount lenses and fitting them for m4/3. Noktor designed a new 50mm f.95 lens for m4/3 and contracted Goyo to do the manufacturing. Goyo engineers may have helped in the design however. SLR Magic then bought out the Noktor company or merged with it or something like that. SLR Magic still sells some of their c-mount type lenses as well as the Noktor lenses and a few others. One of their lenses is a spotting scope with a m4/3 adaptor.
     
  17. burdickjp

    burdickjp Mu-43 Veteran

    235
    Feb 25, 2013
    Maybe not. But designing GOOD lenses is likely much, much harder.

    Have a citation for this?

    I have read reviews. I have looked at the specs. Many people complained about initial quality issues, and the general consensus seems to be that they are not nearly worth their price point.
     
  18. dhazeghi

    dhazeghi Mu-43 Hall of Famer

    Aug 6, 2010
    San Jose, CA
    Dara
    I don't know about being worth it or not, but the images certainly don't look any better than those you see from the C-mount video lenses with similar specifications. If they are new designs, they're not very good.