noa Posted January 30, 2015 Share Posted January 30, 2015 In my search for a wide and fast lens for my GH4 I came across a video of a user that tested a Navitar 8mm f1.4 lens on his GH4 which looked surprisingly good, I do have a 12mm f2.0 lens which is fine for most occasions but often wished I had a wider lens that was at least f2.0 to be able to shoot in dark venues.The supplier of these lenses, Mengel Engineering, is working on a m4/3 adapter as their c-mount doesn't seem to fit regular c-mount to m4/3 adapters and need to be adjusted by the user, the supplier recommended their "VS Technology H1-series 1" 4-8 Megapixel Machine Vision Lens" as they are higher spec then the Navitar lenses and they seem to fit c-mount to m4/3 adapter with just some minor machining.Is there anyone that has experience with these lenses in combination with a GH4, like is there much vignetting and does it retain sharpness across the frame? Is it a lot of work to adjust the adapters to make the lenses fit? The 8mm f1.4 is not exactly cheap (778 euro excl taxes) and since there is hardly any information online or any way to test these I was hoping to find some users that could share their experience. Quote Link to comment Share on other sites More sharing options...
richg101 Posted January 30, 2015 Share Posted January 30, 2015 Generally the high end 'megapixel' lenses are designed for 1" sensors - which are only slightly smaller than the gh4 in 4k mode. However it's normally the 35mm (and above) focal lengths that deliver onto a 1" sensor. extreme wides like a 8mm lens will be aimed at much smaller sensors I'd imagine. probably for 1/3rd of an inch sensors.In order for the lenses to deliver the published specs such as resolving power of 150-200lp/mm, correction for ca, vignette and edge softness over a 1" sensor it means the actual image circle is often a lot lot bigger. I've tested high end machine vision lenses from Schneider, Moritex and Qioptiq. all of which, if publihsed as 1" sensor (<3.6micron px size) will deliver up to aps-c coverage at surprising levels of quality right to the edges. Therefore these lenses are very good for m4/3. However, the c-mount adaptors to m4/3 are often too thick and don;t allow infinity focus. often resulting in no further focus distance than around 1meter. add a link to the lens in question if you can Quote Link to comment Share on other sites More sharing options...
noa Posted January 30, 2015 Author Share Posted January 30, 2015 Thx for your explanation, the manufacturer gave me this link: http://www.mengelengineering.dk/shop/index.php/imaging-optics/machine-vision-optics/5-megapixel-resolution-lenses/vs-technology-h1-series-1-4-8-megapixel-machine-vision-lens.htmlThey said they where going to test a batch of modified M43 adapters in the near future which would be posted when they where done so that might be very interesting, the only concern based from your comment would then be the infinity focus. Quote Link to comment Share on other sites More sharing options...
Julian Posted January 31, 2015 Share Posted January 31, 2015 Those lenses actually look like the new Kowa Prominars for MFT.Kowa is making a 8.5mm f/2.8, designed for MFT.http://www.kowa-prominar.com/special/wide_lens/index.htm Quote Link to comment Share on other sites More sharing options...
richg101 Posted January 31, 2015 Share Posted January 31, 2015 Thx for your explanation, the manufacturer gave me this link: http://www.mengelengineering.dk/shop/index.php/imaging-optics/machine-vision-optics/5-megapixel-resolution-lenses/vs-technology-h1-series-1-4-8-megapixel-machine-vision-lens.htmlThey said they where going to test a batch of modified M43 adapters in the near future which would be posted when they where done so that might be very interesting, the only concern based from your comment would then be the infinity focus. The price point, their 5mpx rating and their 1" capability would suggest they might do exactly what you require. The 35mm will almost certainly cover aps-c. the 25mm will probably be safe on m4/3. after that I imagine those wide lenses are assumed to really be used on smaller sensors like 2/3 and 1/3. 6mm and 8mm on m4/3 is crazy wide and not a regular requirement in machine vision scenarios. whether infinity is achieved or not is gonna be dependent on the rear diameter and whether or not the lens can seat deep enough into the m4/3 mount. if the gh4 had a e-mount all would probably be swell. As Julian has shown, the kowa prominar lens set offers 8.5mm f2.8, which might suggest that closing the aperture down on the 8mm f1.4, and closing it to f2.8 the circle might get big enough to deliver. Personally I'd be looking at a fast 16mm fisheye for full frame (like the distagon 16mm f2.8) and using it with a 0.64x speed booster. price point is about he same. and you'll likely get better coverage of your sensor and less barrel distortion this way. resolution might not quite match the machine lenses but it'll be close. Quote Link to comment Share on other sites More sharing options...
Cinegain Posted January 31, 2015 Share Posted January 31, 2015 Interesting wish. Maybe wait to see what the Olympus 8mm f/1.8 will be like (mock up rumored at CP+, sales in spring, shipping in summer). Quote Link to comment Share on other sites More sharing options...
noa Posted January 31, 2015 Author Share Posted January 31, 2015 Thanks all for the info so far, I know a 8mm might sound crazy wide for some of you but the 12mm f2.0 Olympus lens I"m using now has been too narrow in some cases in the GH4 4K mode, I use that lens on a steadicam (a blackbird) in venues at weddings, during the first dance I want to be able to get the couple on entirely on screen and often that's not possible because I"m too close towards them and can't move back. The 12mm is actually not so wide in such a case.I also need a lens that is at least f2.0, anything slower is useless because I have to work with available light which is often candles, so unless I would get a a7s and spend a lot of money getting it with a fast zoom lens as well I'd like to try a alternative which is why these small c-mount lenses came to my attention, the problem is there is hardly any testfootage available and just getting it to see if it's ok could be a expensive try if it doesn't work out.About that Olympus 8mm f1.8, now that sounds much more interesting, didn't hear about that, thx for the tip! In that case I"ll wait a bit longer to see how much it will be priced. Quote Link to comment Share on other sites More sharing options...
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