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Thread: A superfast normal on the G1

  1. #101
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    Re: A superfast normal on the G1

    dont be worried, its only the fraction of the weight

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    Re: A superfast normal on the G1

    I just got one of the 75/1.9 Switars, but it's not a macro lens. Closest focus is less than 5ft. Sharp lens and covers the sensor! I'm liking the teles primes more and more--sure are alot of nice ones

    Oh, the two 26/1.1 macro Switars I saw are $1100 and $1400. The $1400 is new in the box Too much money for me.

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    Re: A superfast normal on the G1

    wjlapier,
    Switar 75mm f1.9 is an excellent lens and I have one as well. Its just cant focus as close as Macro version but also cost half the price. Its a good time to buy them, I saw them going on feebay for around $300 which is an excellent deal.

    I believe when Oly will introduce their model and as more people will buy in to this format, those Kern marvels will be hard to find and will sell for much more.

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    Re: A superfast normal on the G1

    I haven't seen the 75mm Kern, but I *really* like the 75mm Angenieux f/2.5. A bit slower, but very small, light, and great. It's also seen as a 3" f/2.5, and some versions are labeled Bell and Howell.

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    Re: A superfast normal on the G1

    Quote Originally Posted by monza View Post
    I haven't seen the 75mm Kern, but I *really* like the 75mm Angenieux f/2.5. A bit slower, but very small, light, and great. It's also seen as a 3" f/2.5, and some versions are labeled Bell and Howell.
    Yes, very good lens as well. I sold 2 of them and still have one more left. Angenieux has manufactured some good lenses. Do not underestimate Wollensak, it might be a bit heavier and not as sharp wide open, still good. I might have one coming soon.

    Im thinking on writing a little general guide to c-mount lenses, since I have access to a lot of them. (My friend is in cine business and let me borrows his old stuff. Some of those old glass has many stories behind them). Need to find time to test them.

  6. #106
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    Re: A superfast normal on the G1

    This Sigma lens could look like a good candidate for a fast 'normal'. As they already have lenses with 4/3 mounts, maybe in the future they will bring this one in their line-up with full AF and aperture control.

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    Re: A superfast normal on the G1

    Quote Originally Posted by pix2pixels View Post
    This Sigma lens could look like a good candidate for a fast 'normal'. As they already have lenses with 4/3 mounts, maybe in the future they will bring this one in their line-up with full AF and aperture control.
    I have that lens in EF mount--very nice lens, heavy and big though. I used it a lot on 1.6x bodies but rarely on my 5D.

    I'm curious about the Sigma 30 f/1.4. I've never shot with it, think its available in 4/3rds mount--and its always been a highly debated lens on the Canon forums--though doesn't really qualify for a 'normal'.

    Diane

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    Re: A superfast normal on the G1

    Quote Originally Posted by Diane B View Post
    I have that lens in EF mount--very nice lens, heavy and big though. I used it a lot on 1.6x bodies but rarely on my 5D.

    I'm curious about the Sigma 30 f/1.4. I've never shot with it, think its available in 4/3rds mount--and its always been a highly debated lens on the Canon forums--though doesn't really qualify for a 'normal'.

    Diane
    Sigma 30mm is not bad, a little soft in corners, and I ve heard about non consistency in quality. I bought Leica 25mm f1.4 over a year ago and I love the lens. Arguably the best 50 equivalent of any brand, dpr must review it, seriously. Its heavy and expensive thou, and not easy to find.

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    Re: A superfast normal on the G1

    Quote Originally Posted by Photomorgana View Post
    Sigma 30mm is not bad, (...)
    I bought Leica 25mm f1.4 over a year ago and I love the lens. Arguably the best 50 equivalent of any brand, dpr must review it, seriously. Its heavy and expensive thou, and not easy to find.
    I have owned both these lenses and I tried them in parallel when I used Olympus cameras. Back then I kept the Sigma (after some initial troubles having the lens replaced and recalibrated - the Sigma Scandinavia service center is close to where I live) for the image quality and the size.

    For use on a Panasonic camera I would keep the Panasonic 25/1.4 thanks to the functionality (setting the aperture with the ring and dedicate the front camera wheel for exposure compensation).

    For the G1 I'm not interested in either of the lenses. A manual Sigma never getting sharp across the frame, nah. The big and expensive Panasonic weighting a ton is the opposite to what the µ4/3 system is about for me. If I really need AF and auto aperture and can't wait for the G20/1.7, well, then there is no other option. But that is hardly an idea suddenly popping up, is it?

    fwiw, /Jonas

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    Re: A superfast normal on the G1

    Quote Originally Posted by Jonas View Post
    I have owned both these lenses and I tried them in parallel when I used Olympus cameras. Back then I kept the Sigma (after some initial troubles having the lens replaced and recalibrated - the Sigma Scandinavia service center is close to where I live) for the image quality and the size.

    For use on a Panasonic camera I would keep the Panasonic 25/1.4 thanks to the functionality (setting the aperture with the ring and dedicate the front camera wheel for exposure compensation).

    For the G1 I'm not interested in either of the lenses. A manual Sigma never getting sharp across the frame, nah. The big and expensive Panasonic weighting a ton is the opposite to what the µ4/3 system is about for me. If I really need AF and auto aperture and can't wait for the G20/1.7, well, then there is no other option. But that is hardly an idea suddenly popping up, is it?

    fwiw, /Jonas

    You right its big and heavy, in fact Im having problems using it on E420 as well. Wrist gets too tired. But lenses like leica 25/1.4, and 7-14, and 12-60mm kinda justify a purchase of E3 or E30. (and 50-200 and 150mm also great.../
    But G1 still beats E3 in manual focusing category, so leica R glass could be going for sale...

  11. #111
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    Re: A superfast normal on the G1

    Here's the report on the Navitar 25/0.95. Apparently it covers almost the entire frame and requires no machining.

  12. #112
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    Re: A superfast normal on the G1

    Quote Originally Posted by robertasumendi View Post
    Here's the report on the Navitar 25/0.95. Apparently it covers almost the entire frame and requires no machining.
    I have a Soligor 25/0.95 that's identical to that one... Makes sense since Navitar is somehow associated with soligor.

  13. #113
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    Re: A superfast normal on the G1

    Can you believe the hyperpole spouted by [email protected] sellers (offering lenses for sale 20% above list price from the manufacturer) ?... The 1" Navitar 25mm 0.95 is a tweaked version of a 2/3" lens...it's coverage is max'd out at a 15mm image circle... ... it's not a flat field lens, image quality deteriorates rapidly at the edges.* The only lens the manufacture recommends for going beyond the 1" format is t' Navitar 50mm 0.95 which has edge to edge sharpness, coverage...

    * inside sources...
    Last edited by Y.B.Hudson III; 7th April 2009 at 10:21.

  14. #114
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    Re: A superfast normal on the G1

    Quote Originally Posted by Y.B.Hudson III View Post
    Can you believe the hyperpole spouted by [email protected] sellers (offering lenses for sale 20% above list price from the manufacturer) ?... The 1" Navitar 25mm 0.95 is a tweaked version of a 2/3" lens...it's coverage is max'd out at a 15mm image circle... ... it's not a flat field lens, image quality deteriorates rapidly at the edges.* The only lens the manufacture recommends for going beyond the 1" format is t' Navitar 50mm 0.95 which has edge to edge sharpness, coverage...

    * inside sources...
    If I'm correct and this is the Soligor design... You may be mistaken. Here it is @ F2 on the G1

  15. #115
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    Re: A superfast normal on the G1

    Quote Originally Posted by milapse View Post
    I have a Soligor 25/0.95 that's identical to that one... Makes sense since Navitar is somehow associated with soligor.
    Cool... I didn't know! How's usability with the focus ring so close to the mount? My use for this lens is photographing dancers at clubs where I'm currently pushing iso 3200 1-3 stops to get 1/60 with a 50/1.4

    Y.B. your comments are good to read too, thanks.... Hey, and thanks for the tip on Leica hoods/caps a few weeks back

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    Re: A superfast normal on the G1

    having too much fun with the Olympus Pen F's G.Zuiko 40/1.4. Even though I missed the focus on these two a little bit, I like what it does:






    Both with the Panasonic G1 + Olympus G.Zuiko 40/1.4, wide open at ISO 100. Exposure times 1/30 and 1/100 sec, respectively.

    enjoy,

  17. #117
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    Re: A superfast normal on the G1

    Dear all;

    While not superfast, and just on the long side of normal, I have mounted my Nikon 28mm F2 AIS on the G1, and got the following results:



    I also did a brick wall test, and an infinity test, the photos can be found at the following link:

    http://www.jonesii.net/2009%2004%200...mal/index.html

    Dave

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    Re: A superfast normal on the G1

    Just a minor addition to this one unless I have overlooked it - a few pics with the Kodak Cine Ektar 25mm/1.4. Right before I put on the lens I managed to get a drop of water on the sensor, so I didn't take more and you can see it a bit on some of them. Minimal vignetting in the corners at 16/9. The hand picture is cropped a bit, the other 2 are JPGs straight from the camera. Oh, and that's Queen Kapi'olani and some banyan tree roots in Kapi'olani Park, Waikiki. It does take a bit getting used to the manual focusing, especially in the bright light around the beach, but overall I like the lens. I still have to try it wide open in a darker place, though...

    Stefan

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    Re: A superfast normal on the G1

    Had a few minutes for shooting today. I think I need to double-check the dioptre setting before I shoot, I had a few focus problems... I liked the three bushes next to each other, each in a different state of bloom. Taken with the Cooke Kinic 25/1.5, fully open, no cropping, only very minimal sharpening and a touch of saturation on the grey one (in AP Elements 6).

    The other 2 were from taken on the Chinese cemetery (Manoa Valley, Honolulu), the angel was stopped down a little bit.

    Stefan











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    Re: A superfast normal on the G1

    Quote Originally Posted by Godfrey View Post
    having too much fun with the Olympus Pen F's G.Zuiko 40/1.4. Even though I missed the focus on these two a little bit, I like what it does:
    Godfrey - did you adapt the lens yourself or does someone now have a Pen F lens adapter for sale?

    Keith

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    Re: A superfast normal on the G1

    There is a Pen F adapter for sale from Hawk, it's actually the same as his c-mount adapter. It works with Pen F lenses via a Pen F extension tube flange which screws into the front of the adapter. He's supposed to be designing his own flange, but it's not ready yet.

    If anyone wants to use Pen lenses, drop me a PM, I have some spare extension tube sets.

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    Re: A superfast normal on the G1

    Quote Originally Posted by woodmancy View Post
    Godfrey - did you adapt the lens yourself or does someone now have a Pen F lens adapter for sale?
    I am using an adapter made by screwing the lens mount portion of a Pen F extension ring set into a micro-FourThirds telescope mount flange adapter (available for $43 from Hutech). This is essentially identical to what Hawk is producing at present and works well, but the Pen F extension ring sets are a little hard to find.

    jinfinance is working on a direct Pen F to micro-FourThirds adapter. I thought it would be available by now but last I talked to him he was delayed a couple of weeks. I'll send him another note ... I'd like a second one so that each of my Pen F lenses (40/1.4 and 70/2) will be easy to handle.

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    Re: A superfast normal on the G1

    The difference between the Hawk and the Hutech is that the focus scale is oriented properly with the Hawk adapter, and it's a correct 50mm thread instead of 49.8mm on the Hutech which is close, but not quite a match to the Olympus extension rings.

    Not sure what is up with Jinfinance, he first said March for the Pen adapter...

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    Re: A superfast normal on the G1

    Quote Originally Posted by monza View Post
    The difference between the Hawk and the Hutech is that the focus scale is oriented properly with the Hawk adapter, and it's a correct 50mm thread instead of 49.8mm on the Hutech which is close, but not quite a match to the Olympus extension rings.

    Not sure what is up with Jinfinance, he first said March for the Pen adapter...
    Thanks! The Hutech thread is close enough, in practical use. Actually, the odd position of the focus scale lets me see the aperture markings on my FT series 40/1.4 lens more easily. I only rarely look at the distance scale for this long a focal length as I focus it through the viewfinder. Since I put the 40 on the adapter, I've only rarely taken it off: the position doesn't bug me.

    Yeah, jinfinance told me ten days about three weeks ago. Must be busy.

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    Re: A superfast normal on the G1

    Quote Originally Posted by Godfrey View Post
    (...) the odd position of the focus scale lets me see the aperture markings on my FT series 40/1.4 lens more easily.
    It owuld be great with a direct and proper adapter.
    The aperture ring and the markings... On my 40/1.4, and I guess they are all made the same way, you can pull the aperture ring towards the front of the lens and then turn it 180 degrees. That way you can chose between the Pen index numbers or the normal f-stop values.

    I hope Hawk or jinfinance or anyone make agood adapter, and ship it some time soon.

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    Re: A superfast normal on the G1

    Hawk is shipping. Here is a photo of the extension flange on a Hutech adapter (49.8mm thread to micro 4/3.) The red dot needs to be at about 2 oclock for proper lens orientation. Sometimes removing the lens is tricky as it's a bit too easy to unscrew the flange, but it works.


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    Re: A superfast normal on the G1

    Quote Originally Posted by Godfrey View Post
    (...) I'd like a second one so that each of my Pen F lenses (40/1.4 and 70/2) will be easy to handle.
    You have the 70/2. Great! I'm interested in that lens. Do you have any words on how it performs?

    thank you, /Jonas

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    Re: A superfast normal on the G1

    Quote Originally Posted by Jonas View Post
    It owuld be great with a direct and proper adapter.
    The aperture ring and the markings... On my 40/1.4, and I guess they are all made the same way, you can pull the aperture ring towards the front of the lens and then turn it 180 degrees. That way you can chose between the Pen index numbers or the normal f-stop values.
    Didn't know that, cool. ;-)

    But the external aperture ring mechanism is a bit gummed up on this one and I won't force it ... should get a CLA but eh? The lens works beautifully as is, so I'm leaving it alone.

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    Re: A superfast normal on the G1

    Quote Originally Posted by Jonas View Post
    You have the 70/2. Great! I'm interested in that lens. Do you have any words on how it performs?
    It's a slender, pretty piece ... much like the 40/1.4 but about an inch or so longer. I have it fitted with a B+W Telephoto metal lens hood (49mm on a 43->49mm step up ring). Imaging qualities are much like the 40/1.4 too. Four quick examples ...








    All taken between f/2 and f/2.8.

    I haven't used it much as yet, it's a bit longer than I normally shoot with, but I'm pleased with it. It was a bit on the pricey side of things.

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    Re: A superfast normal on the G1

    Quote Originally Posted by Jonas View Post
    It owuld be great with a direct and proper adapter.
    The aperture ring and the markings... On my 40/1.4, and I guess they are all made the same way, you can pull the aperture ring towards the front of the lens and then turn it 180 degrees. That way you can chose between the Pen index numbers or the normal f-stop values.
    That is a preset mechanism and is only available in Pen FT lenses. The Pen F lenses do not have the pen numbering (that was for metering) and do not have that. So, if you do not see the pen FT (whole) numbers or see a sticker (instead of engraved numbers), pulling and trying to twist that ring could damage the aperture!

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    Re: A superfast normal on the G1

    Quote Originally Posted by Vivek View Post
    (...) So, if you do not see the pen FT (whole) numbers or see a sticker (instead of engraved numbers), pulling and trying to twist that ring could damage the aperture!
    Ah. Oh. Thank you Vivek. I'll remember that in the future! Regards, /Jonas

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    Re: A superfast normal on the G1

    Quote Originally Posted by Godfrey View Post
    Didn't know that, cool. ;-)

    But the external aperture ring mechanism is a bit gummed up on this one and I won't force it ... should get a CLA but eh? The lens works beautifully as is, so I'm leaving it alone.
    Yes, it is cool. But I didn't know about the difference between the F and FT lenses (Vivek's post). Anyway, it doesn't matter a lot what numbers there are. As I'm used to f-stop values it felt natural to set them to show, that's all.

  33. #133
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    Re: A superfast normal on the G1

    On the Pen F lenses (with just f/stops and no meter numbers) it's not really possible to pull up the aperture and turn, as on the Pen FT lenses...if one were able to accomplish that, yes, the lens would be seriously damaged.

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    Re: A superfast normal on the G1

    i've got a macro switar 26mm f1.1 and a jinfinance c-mount to mFT adapter on its way.

    is a shim needed since this is a bolex rx lens??

    i came across this:

    From lensseat to filmplane is 20.76mm in the Bolex H16 RX, while it is 17.52mm in a C-mount camera.

  35. #135
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    Re: A superfast normal on the G1

    "is a shim needed since this is a bolex rx lens??"...

    no... the 26mm switar will focus a little past infinity with close focus distance at 18cm±... with the focus throw at 590° ±...

    A 3mm shim would not leave enough exposed threads to mount the lens...



    regards Hudson

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    Re: A superfast normal on the G1

    great news. i was afraid that i wouldn't be able to focus to infinity.

    now the long wait for the adapter...

  37. #137
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    Re: A superfast normal on the G1

    Quote Originally Posted by Y.B.Hudson III View Post
    "is a shim needed since this is a bolex rx lens??"...

    no... the 26mm switar will focus a little past infinity with close focus distance at 18cm±... with the focus throw at 590° ±...

    A 3mm shim would not leave enough exposed threads to mount the lens...



    regards Hudson
    Thanks for the info - I hope that also works for the 50/1.4RX that should be over one of the oceans between England and Hawaii right now

    Stefan

  38. #138
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    Re: A superfast normal on the G1

    Quote Originally Posted by lcubed View Post
    i've got a macro switar 26mm f1.1 and a jinfinance c-mount to mFT adapter on its way.

    is a shim needed since this is a bolex rx lens??

    i came across this:

    From lensseat to filmplane is 20.76mm in the Bolex H16 RX, while it is 17.52mm in a C-mount camera.
    That "information" about Bolex flange distances is all over the Internet, but when we discussed this before I think the consensus we reached is that it's incorrect.

    According to this 1974 technical bulletin from Bolex, which I found on the Bolex Collector website: All Bolex C-mount lenses, whether RX or not, have the same back focus distance (in air) of 17.52mm. This suggests there should be no reason to shim the lens to use it on your G1, since there's nothing but air between the back of the lens and the imager.

    The 20.76mm distance you sometimes hear about is based on a misunderstanding about how Bolex dimensioned their reflex and non-reflex cameras. The reflex prism in the RX models displaced the image rearward slightly. (Actually, ANY parallel-faced block of glass you put behind a lens will displace the image rearward by about 1/3 the thickness of the block.)

    Specifically, the Bolex prism is 9.5mm thick and displaces the image by 3.24mm. This meant that a lens set up for the standard 17.52mm back focus distance would actually form its image through the prism at 20.76mm, and the RX bodies were dimensioned to allow this extra distance. Without the prism, though, the same lens would form its image at the standard 17.52mm.

    So if reflex and non-reflex lenses focused at the same distance, why did Bolex offer a special RX version of some lenses? According to the same paper, it was because the prism block introduced spherical aberration in some lenses (mostly shorter ones) and the RX-series lenses were designed to take this into account and neutralize it. That means that an RX lens used on a non-RX camera (such as your G1) probably won't perform as well as a non-RX lens when used at its widest apertures. The remedy is simply to stop the lens down a bit when sharp results are critical.

    If you really want to dig into this further, a cinematographer named Dennis Couzin wrote a very detailed analysis in 1976, along with several follow-up articles. Couzin's "Revised RX Rule" of 1978 posits:

    RX-mount lenses work well on C-mount cameras provided they are used (for focusing and taking) stopped down past about f/2.8 and provided they meet the exit pupil test.

    Exit pupil test: Stop down a lens and view it from the rear. If the pupil appears deep set in the lens, an inch or more back from the mount, then the lens passes. If it appears shallow in the lens then the lens fails, and even with much stopping down will not give good corner images used o the opposite kind of camera [RX vs. non-RX.]

    I suspect that the different spherical aberration correction given to RX vs. non-RX lenses may be the cause of the semicircular "swirlies" we see in the corners of some G1 pictures made with Bolex lenses, when other examples of apparently the same lens don't produce the same effect. But I don't have any way to investigate that. Maybe if you post some pictures made with your RX Switar we can all compare them to pictures made with similar non-RX Switars, and we'll be able to see whether my guess is true or not.

  39. #139
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    Re: A superfast normal on the G1

    Thanking Ranger9 for getting the matter of the Bolex RX-mount lenses mostly correct.
    Actually it's an oversimplification to say that the RX-mount lenses and C-mount lenses have identical 17.52mm backfocus (in air). The backfocus is identical for the paraxial rays -- the rays left after the lens is greatly stopped down. But the backfocus is significantly different for marginal rays -- the first rays removed as the lens is stopped down from full open. In Figure 3 of my 1976 "The Truth about the Bolex Prism" this difference is the distance from point P to point Q. [Thankfully that one figure wasn't distorted by whoever copied the original 1976 article for Ranger9's first link, but thE copiest omitted the distance scale from the figure. Readers of the 1976 article should better look at the original posted at Ranger9's second link.] For an f/1.1 RX-mount lens the distance from P to Q is about 0.28mm. Properly speaking, there is no backfocus measurement for such a lens.

    The following improved version of the RX/C Rule appeared in the 1987 article (also available at Ranger9's second link):
    A C-mount lens works well on a RX camera or a RX-mount lens works well on a C camera, if and only if:
    (1) the lens is slower than about f/2 or f/2.8, or stopped down this far;
    AND (2) the lens has deep set exit pupil, about 1½ inches or farther into its screw mount.

    Thus the 26mm f/1.1 Macro-Switar, being an RX-mount lens, is a very poor choice of "superfast normal" for the G1 camera (unless you plan to mount a 9.5mm thick pane of glass behind the lens to compensate its RX-mount aberrations).

    In general, this strand's fascination with using C-mount lenses on the G1 is optically perverse. The C-mount lenses were mostly designed to cover the 16mm cine frame having image diagonal about 12.6mm. The G1 camera sensor has diagonal about 21.6mm. "Covering" in photographic optics doesn't mean simply "putting light onto". That some C-mount lenses don't vignette much of the G1 frame should not suggest that these lenses are optically corrected for that oversize area. Actually, well-designed 25mm lenses for 16mm cine (like the Zeiss Distagon 25mm f/1.2) are already losing correction at the extreme 12.6mm diameter. They pack their sharpness into the intended frame area. By 16mm diameter they are perhaps 1/10 as sharp as at 10mm diameter.

  40. #140
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    Re: A superfast normal on the G1

    In general, this strand's fascination with using C-mount lenses on the G1 is optically perverse.
    ..
    ..


    They pack their sharpness into the intended frame area. By 16mm diameter they are perhaps 1/10 as sharp as at 10mm diameter.
    Optically perverse. Love that.

    Do you know of any lens that does not drop sharpness (and other corrections) from the center, that is made for still cameras?

  41. #141
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    Re: A superfast normal on the G1

    Quote Originally Posted by dcouzin View Post
    Thus the 26mm f/1.1 Macro-Switar, being an RX-mount lens, is a very poor choice of "superfast normal" for the G1 camera (unless you plan to mount a 9.5mm thick pane of glass behind the lens to compensate its RX-mount aberrations)
    It is only necessary to collimate the 26mm/1.1 for the G1. After that, it works very well on the G1. My experience. More details in the following thread:

    http://forum.getdpi.com/forum/showthread.php?t=9593

    Cheers
    Peter
    Peter Werner
    Leica M8, R9+DMR & Digilux 2; Nikon D700; Panasonic FX01, FX150 & G1; Samsung TL350 (WB 2000)

  42. #142
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    Re: A superfast normal on the G1

    Quote Originally Posted by dcouzin View Post
    Thanking Ranger9 for getting the matter of the Bolex RX-mount lenses mostly correct.
    You're mostly welcome :-) It's not easy to be exact when you have to Google up references from all over the map!

    In general, this strand's fascination with using C-mount lenses on the G1 is optically perverse.
    Some of it may be perversity and some of it may just be frustration at the current lack of compact, wide-aperture alternatives in these focal-length ranges. When the Micro Four Thirds-native Panasonic 20/1.7 finally appears, I'll probably retire my C-mounts except for special purposes.

    Still, since there ARE so many C-mount optical perverts here, though, and since you seem to be the person who has done the deepest thinking on the RX issue... maybe you'd like to write up a summary that could stay in the forum, so people don't have to keep finding my post and then chasing down all the links...?

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    Re: A superfast normal on the G1

    Quote Originally Posted by Ranger 9 View Post
    Still, since there ARE so many C-mount optical perverts here, though, and since you seem to be the person who has done the deepest thinking on the RX issue... maybe you'd like to write up a summary that could stay in the forum, so people don't have to keep finding my post and then chasing down all the links...?
    That suggestion is great but would only be helpful if dcouzin actually has any user experience of these lenses, especially for photography.

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    Re: A superfast normal on the G1

    A typical example of an "optical perversion".



    Panasonic G1, Computar-TV 25/1.3.

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    Re: A superfast normal on the G1

    Quote Originally Posted by dcouzin View Post
    Thanking Ranger9 for getting the matter of the Bolex RX-mount lenses mostly correct.

    In general, this strand's fascination with using C-mount lenses on the G1 is optically perverse.
    For better or for worse I have a Ph.D in Physics - I never made my living from it, but that's my problem.
    I schooled at Reading University and the Physics department was headed up by R W Ditchburn who was an expert on light and optics, and wrote a number of seminal works. I couldn't understand a word he talked about, even though I was heavy into photography - such a pity. I've picked up much more about the practical issues of lenses in these forums.

    Onwards and upwards - Vivek has taught me more than Ditchburn. But I'm not going to buy Vivek's recommended camera case

    Keith

  46. #146
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    Re: A superfast normal on the G1

    Quote Originally Posted by Vivek View Post
    Optically perverse. Love that.

    Do you know of any lens that does not drop sharpness (and other corrections) from the center, that is made for still cameras?
    Sure, this is often the case for narrow angle lenses, like 135mm lenses for 35mm still format (43mm diagonal).
    The matter has nothing to do with still versus cine. Anyone designing a "normal" angle lens can see that field coverage cannot come without compromising the center. Different manufacturers have different "philosophies" concerning this tradeoff. The Zeiss Distagon I cited is designed to "cover" a 12.6mm circle. Wide open, sharpness is actually greatest at about 5mm off center. Sharpness declines rapidly past about 5.5mm off center. So only the very corners of the intended image are noticeably less sharp than the center. Zeiss knows what they're doing. My point was that by 8mm off center, which is as far as they published data for this lens, the sharpness is gone.

  47. #147
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    Re: A superfast normal on the G1

    Quote Originally Posted by Ranger 9 View Post
    Some of it may be perversity and some of it may just be frustration at the current lack of compact, wide-aperture alternatives in these focal-length ranges.
    You have a 21.6mm diagonal sensor and you want a certain angle of view corresponding to about 25mm focal length. This is a wide-angle lens and you won't find solutions among lenses designed as normal-angle lenses for 16mm cinema (image diagonal 12.6mm) or super 16mm cinema (image diagonal 14.5mm).

    Your image diagonal is considerably smaller than that of 35mm cinema (about 27.2mm) and smaller yet than 35mm "half-frame" still (about 30mm). You would find these lenses sharp over your whole sensor. Not as sharp as lenses designed for your format, but sharp enough. But they're expensive.

    It is a tough practical problem to have an image sensor with no suitable photographic lenses. Narrow angle lenses can be home-made but not wide-angle lenses. A possible solution is to mount a cheap 50mm lens with adequate coverage and then to stick a cheap 0.5× wide angle adapter in front of that.

  48. #148
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    Re: A superfast normal on the G1

    Quote Originally Posted by petermcwerner View Post
    It is only necessary to collimate the 26mm/1.1 for the G1. After that, it works very well on the G1. My experience.
    Post #91 (Photomorgana) in this strand shows two pictures made with the 26mm f/1.1 Macro Switar RX lens. The one shot at f/1.1 is grossly unsharp. Look at the lower eyelid hairs. The one shot at f/1.8 looks pretty sharp (in the low resolution JPEG posted). Are your results better?

    It is conceivable that Kern made some 26mm f/1.1 Macro Switars which were not RX-type. These would be true C-mount lenses and not require the 9.5mm glass pane between them and the image. If they exist, and if you luckily found one, then your experience won't match Photomorgana's or the other less lucky f/1.1 users.

    And how sharp is your image 8mm, 9mm, 10mm off the center?

  49. #149
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    Re: A superfast normal on the G1

    Quote Originally Posted by Ranger 9 View Post
    ... maybe you'd like to write up a summary that could stay in the forum, so people don't have to keep finding my post and then chasing down all the links...?
    My last article on RX and C was in 1987.
    The short answer today is: avoid RX-mount lenses. They are lenses designed for a 9.5mm pane of BK7 glass between them and the image. Such a pane introduces spherical aberration, astigmatism, and chromatic aberrations. The RX lens is designed with a load of aberrations to cancel those of the pane, so the RX lens without the pane is an incomplete optic. Why pay big money for an incomplete optic unless you happen to own a camera, namely the Bolex H16 REX, which has the completing 9.5mm thick pane in front of the image plane?
    Similarly, for large NA (like small f-number) miicroscope objectives you generally need a different lens when there will be a cover glass over the specimen.
    Similarly lenses for 3-sensor video cameras are designed with aberrations to cancel those of the camera's prism systems. You would not be happy using one of these lenses on a 1-sensor camera.

    I lived near the American Science Center in Chicago in its heyday when it got the surplus of Bell & Howell. The risk in buying mystery lenses cheap is that you don't know whether they are optically complete. (You also don't know what wavelengths, what image surface, what magnification, etc. they're intended for.) The enthusiasts in this room have enough uncertainty about their C-mount lenses. They don't need the addition of the RX problem.
    Last edited by dcouzin; 21st August 2009 at 21:16.

  50. #150
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    Re: A superfast normal on the G1

    All too true. Fortunately, a lot of these lenses are cheap enough that we can just buy them and try them out to see if we like the pictorial effects they produce.

    I don't always care if my pictures are sharp, as long as they're pretty -- although I realize that as a professional cinematographer you can't afford to take such a cavalier attitude!

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