Pentax/Cosmicar/Navitar/Naviton 75mm F/1.4 anyone have it?

fatdeeman · Joined: 13 Jun 2009 Posts: 780 Location: UK

I just picked this one up for a good price (well I have seen them sell for more than I paid at least)

Has anyone tried it?

It seems to go under a few different names but is the same basic lens.

I read on a French forum that the metal around the rear element will come into contact with the light baffle inside the micro 4/3 lens mount, I have a few lenses in c mount where the rear element goes slightly past the baffle (but still far enough away from the shutter to be safe) but here the rear element is too wide to get past the baffle so you can't reach infinity. It seems if you shave a few mm of the metal away the lens will reach infinity but you are working very close to the glass so it's a bit nerve racking!

Does anyone know how far the rear of the lens can protrude past the rear of the cmount adapter and still be safe?

The forum mentions the Navitron variant, I do not know if the rest need the same mod but I can't see why they would be different but on the other hand I haven't read about it needing modification elsewhere and have seen it sold on ebay advertised as being able to focus to infinity but that may have been a modified lens.

The French thread is here:

http://panasonicfz.easyforum.fr/t54581-vds-75mm-14-en-monture-c-modifies-pour-micro-4-3

What's interesting is that the lens is made for 1" sensors so it may give full coverage on the Sony NEX!

fatdeeman · Joined: 13 Jun 2009 Posts: 780 Location: UK

I found out that some versions of the lens do not have the infinity problem because the lens design varied very slightly over the years, it seems to be a case of getting the right version so I have my fingers crossed!

edz · Joined: 20 Aug 2009 Posts: 82 Location: UK

at infinity:

fatdeeman · Joined: 13 Jun 2009 Posts: 780 Location: UK

Just recieved the lens, the rear element doesn't come close to protruding past the mount, even at infinity so that's a good sign, I'll try it out tonight, knowing my luck something else will be wrong with it!

rbelyell · Expire: 2014-01-31

i have the cosmicar version in silver and i have no infinity problem. the lens is very nice in low light and i find very pleasing color saturation. good luck!

fatdeeman · Joined: 13 Jun 2009 Posts: 780 Location: UK

I've just tried it out quickly, it's fairly sharp wide open but there is a fair amount of CA, it's the first fast aperture lens I have had beyond 50mm so I'm sure it's partly a matter of focusing.

It's hard to get focus right because there's some glowing and when the glowing is minimized the focus is off and when the focus is right the glowing is worse so I get stuck trying to make the best compromise but some practice will make it better.

Bokeh wide open is gorgeous, stopped down is great too apart from highlights due to the jagged aperture shape which I don't mind normally but at the edges you get the cat's eye effect so the bokeh is half curved and half hexagonal!

I have no idea if the version with the protruding element performs better but the lens seems quite good so far. Obviously it is sharper as you stop down and is razor sharp by the time you get to F/4.

A couple of samples coming up!

fatdeeman · Joined: 13 Jun 2009 Posts: 780 Location: UK

The sharpness wide open isn't amazing but not bad and it's consistent to the edges which is good

Bokeh Example:

First impressions are it's not bad but not as good as the French guy on the French forum claimed, that might be because the version with protruding element is better or because he was selling them and was over hyping them!

Can't wait to try some portraits!

As for cost, I bought the lens and two Sony CCTV cameras for �35, I have sold one of the cameras to a friend for �25 so the lens cost �10 so far minus whatever I can get for the other camera which might be quite a lot if I'm lucky as it seems to have been quite expensive when it was new!

Now I just need this miserable weather to pass so I can get outside with the lens!

Nordentro · Expire: 2015-01-29

I think I have it if it's the same as this Surprised

fatdeeman · Joined: 13 Jun 2009 Posts: 780 Location: UK

Looks the same to me, rubber grip might be a different pattern but otherwise it looks the same!

fatdeeman · Joined: 13 Jun 2009 Posts: 780 Location: UK

The more I try this lens the more disappointed I am, I thought it would be sharp in the centre wide open like others have claimed.

There's something strange going on between all the ghosting and glowing, when you focus with live view the image seems to come into focus twice, it's almost like the contrast and resolution are separate slightly! You can get the image to look as focused as it's going to get with decent contrast but if you keep turning the ring a tiny bit first it goes out of focus and the contrast goes down and the flaring and ghosting appear and then suddenly the actual detail becomes sharp again! It's as if the light rays never align completely on the sensor.

Some of my shots seem sharper at the edges than the centre which I think is down to the same thing, when you have a sharpish image in liveview with decent contrast and no ghosting there will be another plane of focus with worse contrast and more ghosting but better actual detail, It's hard to explain really...

I have seen so many people say it's sharp wide open and say it has to be sharp because it's a machine vision lens so the results are a little disappointing to me. It's much much better a F/2 but I suppose that defeats the object of having an F/1.4 lens. This is the softest C-mount lens I have had wide open, it's worse than that little 25mm F/1.4 that you can buy for almost nothing on ebay.

I guess I could keep it for now and use it at F/2 but the highlight bokeh is ugly at F/2 because at the edges it's half curved and half hexagonal :/

Perhaps there is something amiss inside although it doesn't seem to have ever been tampered with or dropped, maybe it's just not a great example?

Here's the difference between F/1.4 and F/2

I have used a hood but it doesn't have any major effect, sharpness seems a bit better for middle distance subjects but I guess you could say that about a lot of lenses. I'll play with it some more and see what happens.

pat donnelly · Posted: Fri Mar 04, 2011 2:30 pm Post subject: 75mm fast lenses

I have two of these as unnameds, black machine vision (navitron) types and am very pleased with rendition!

I got a Silver, Cosmicar cine lens version that was very disappointing. Lots of glow, so much, that it must have been messed with internally? Nordentro got at least one excellent version.

The 1.4s are great but stay away from the 1.3 types! These are the ones with infinity problems and are incapable of focussing more than a couple of metres. Very good performers at that (have two!) but trying to grind away the metal is too much for my heart! Damaged the mount in one and left the other well alone.

fatdeeman · Joined: 13 Jun 2009 Posts: 780 Location: UK

I haven't ruled out the adapter because my other longer c-mount lens (a canon tv zoom) also gives inconsistent results whereas I never have problems with shorter focal lengths so perhaps the adapter isn't quite right, I have a higher quality metabones adapter on the way.

If it still disappoints I'll just throw her back in and fish for another copy!

Nordentro · Expire: 2015-01-29

Looks like you could have a bad copy?!? Surprised

I would rate mine is quite good wide open.

jlduh · Joined: 25 Dec 2011 Posts: 4 Location: France

Hi, I'm the "french guy" (jlduh) who initiated the thread on the french Panasonic forum mentioned above.

I read many errors and here and there concerning these lenses that I contributed to discover for use on micro 4/3 because I had several ones from an old stock (new though) that I couldn't use on anything except C-mount film camera (16mm). Getting very early a G1 and understanding the full potential of this concept without mirror especially for old lenses, and especially c-mounts, i experimented on many and discovered that this one was exceptional but needed some modifications to limit risks of intrusions inside the camera which could result in interferences and limited focus range.

When I read that Cosmicar and Pentax 75mm c-mounts are the same ones I can guarantee that THIS IS NOT TRUE, they are definitely other lenses (Cosmicar is the Pentax brand for industrial and CCTV lenses by the way).

The Navitar 75mm has been sold under various distribution names like Ernitec, Tarcus, Computar (but NOT PENTAX or COSMICAR). There has been probably some little variations in the specs but they do not differ hugely (I mean the Navitar/Computar, Ernitec, Tarcus ones, the Cosmicar Pentax has nothing to do with those).

The Cosmicar 75mm (silver) is known to have more CA and aberrations around edges, and so is not as sharp as the Navitar, because it is a different lens...

Having said that, I don't know which lens you have fatdeeman. And of course I'm sure there are Navitars/Computars etc. that have problems because some people dismantled them and created problems like on any other lenses, I don't know if it's the case with yours but the images look definitely soft to my eyes with lot of CA and "glow", the ones that Nordentro posted fit perfectly with results that I get and that other people who bought some from me got, all have been happy with those and I personally hope that Pana will get soon a decent focus peaking option like on the NEX cameras because this will make this lens very easy to use! Come on Pana!

You can download below a full res image taken at 1,4 with one of my Navitars 75mm on a G1, the focus is precisely on the left eye of the guy. This is straight from G1, no processing from any kind, and it has the same look than some of the portrait pictures Nordentro posted. (SORRY I HAVE PROBLEM POSTING THIS LINK ON THE MF FORUM, IT DOESN'T APPEAR, ANY HELP?)

All the ones that I have or that I have sold have been tested on G1 and have the same caracteristics, very sharp at center even wide open, limited CA, and very pleasing bokeh. Some can protude more or less going towards infinity (I guess variations in helicoid setup or assembly) that's why I modify them to avoid any problem on any combinations of cameras (that I cannot test of course, but my philosophy is that it shouldn't protrude more than a few ten's of mm from the back side of C-mount adapter, which is already recessed inside the camera in fact, all of this is tight on C-mount on micro 4/3 and parts inside the camera are very close).

I got some lenses bought recently by Video Prod companies in France for use on GH2 and i'm sure this lens is also a very good one for video (again video focus peaking will enhance the practical usability of this one...).

It's light (360g), small even with adapter (basically the volume of a 14-45 Lumix zoom), you just have to be careful with flare (very big frontal convex glass, so a hood is to be considered).

But again, Cosmicar and Pentax are not the same...

Some cosmicars can be good though (there are tons of versions!), I have a Cosmicar 50mm 1,4 (old silver version) and it is indeed a very good lens, with good mechanical construction and quite sharp (and small) with a little bit of glow at 1,4 but very decent really.

Nordentro · Expire: 2015-01-29

jlduh · Joined: 25 Dec 2011 Posts: 4 Location: France

Thanks Nordentro for your welcome!

Yes probably the anti spam creates the problem, I didn't find a way to post the picture...

And yes again concerning the Ampex 50 1.4 which is a rebadging of the Cosmicar that I have, i second your observations; but globally a very nice lens.

The nice thing with these cosmicars is that it's very easy to unscrew the helicoid (just by removing at first the aluminium part at the back of the lenses) and so you can go much closer (close focus) than normal setup. Just be careful not to go too far doing this otherwise the helicoid comes off and it's a little bit tricky to put it back.

With the 12,5mm cosmicar 1.4 doing this i can go to focus close to a few centimeters from the subject which is nice...

But this is a bit out of topic Razz

maxuser · Joined: 28 Apr 2012 Posts: 1

I had 3 of them: Cosmicar 75/1.4 and 2 x Navitar 75/1.3 - all black and looking very similar.
In my tests Navitars much better than Cosmicar. Cosmicar a little better in vignetting (I've never seen dark corners on pictures from it), but much worse in SA wide open. All 3 have sensible CA wide open, but also good contrast and sharpness. Geometry isn't so good))

nemesis101 · Expire: 2015-01-22

I have an 'Apollo' version which is slightly longer in focal length but otherwise identical to the 'TV Lens' blach version - I have posted about it before. It's my best lens on the G2 bar none, very sharp, great bokeh etc. I suspect maybe yours might be decentred or??

Doug

IAZA · Joined: 16 Apr 2010 Posts: 2587 Location: Indonesia

I just bought Cosmicar 75/1,4
sharp start f2, wideopen soft
samples

crop 100%