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Aero-Ektar in MF mount (Was: What's this? (Unknown 180/2.2))
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PostPosted: Sat Sep 17, 2011 11:24 pm    Post subject: Reply with quote
Yes, but if your housing is 14.5cm long and has a register of 74.1mm (Pentacon 6) that means the back of the lens is only 106mm from the film plane.

No way could that lens be an Aero Ektar, just look at the length of those 35mm housings with Aero Ektar 2.5/178s mounted on them - the distance from the back of the Aero Ektar to the film plane is a hell of a lot more than 106mm, I would estimate it is more like 200mm.

It's not possible to mount an Aero Ektar 2.5/178 106mm from the film plane and get an image with any sort of focus, I would, at a guess, say that the Aero Ektar would need to be placed 178mm from the film plane.

Also, the aperture ring on your lens is at the front, the Aero Ektar's aperture ring is set back behind the front element by a couple of cm.

Have you got any picture of the lens when it was out of it's housing?


PostPosted: Sun Sep 18, 2011 12:15 am    Post subject: Reply with quote
This page (http://www.johndesq.com/graflex/aeroektar.htm) gives back focus length = 122mm so it may vary in different versions I guess. Also aperture ring is part of new housing, it's not where actual aperture located.

I didn't take it out of the housing (and I don't want to do this and actually don't know how to). I disassembled what I could and have these pictures (ordered from front to back of the lens):

Front element: http://www.flickr.com/photos/mifki/6156751151
Serial number on it: http://www.flickr.com/photos/mifki/6157300454
Second group of two elements: http://www.flickr.com/photos/mifki/6157292234 http://www.flickr.com/photos/mifki/6156747367

Then what you see after screwing out front part with above elements.
Aperture and third group of two elements behind it: http://www.flickr.com/photos/mifki/6157294586

And rear element: http://www.flickr.com/photos/mifki/6157296208 http://www.flickr.com/photos/mifki/6157297930


PostPosted: Sun Sep 18, 2011 1:59 am    Post subject: Reply with quote
It is confusing, but regardless, it's a very good lens and that is what matters.


Maybe someone familiar with Aero Ektars knows more?


PostPosted: Sun Sep 18, 2011 2:20 am    Post subject: Reply with quote
I own an AE, and I must say, this looks a lot like it.

I wonder, if, during the course of the modification, the modder was able to rearrange the elements so that

(a) s/he was able to increase the focal length by 2mm (178mm -> 180mm), and;
(b) condense the image circle (i.e., make it smaller than the original) and therefore increasing the f-stop (f2.5 -> f2.2)

?



PostPosted: Sun Sep 18, 2011 3:02 am    Post subject: Reply with quote
rawhead wrote:
I own an AE, and I must say, this looks a lot like it.

I wonder, if, during the course of the modification, the modder was able to rearrange the elements so that

(a) s/he was able to increase the focal length by 2mm (178mm -> 180mm), and;
(b) condense the image circle (i.e., make it smaller than the original) and therefore increasing the f-stop (f2.5 -> f2.2)

?


a) Do not take '180' as exact value. I was told that it's 180mm when bought it, there's no focal length written on it. So maybe it's still 178mm.

b) Unfortunately I currently don't have spot-meter or anything more precise than TTL prism to check if it's really f/2.2, maybe I will do this later.

Image circle is more interesting question. AE covers 5"x5". So with such crop-factor on my 6x6cm Hassy its effective focal length should be around 376mm, right? Actually it is definitely not so much. From my measurements its effective focal length is about 210mm. This is strange. So maybe it was really modified somehow but it's hard to tell without side by side comparison or it is some special version of AE.


PostPosted: Sun Sep 18, 2011 3:11 am    Post subject: Reply with quote
Like I said, it's confusing, some pieces fit with it being an AE, some don't.

Maybe it has been modified?


PostPosted: Sun Sep 18, 2011 3:34 am    Post subject: Reply with quote
pronvit wrote:
Image circle is more interesting question. AE covers 5"x5". So with such crop-factor on my 6x6cm Hassy its effective focal length should be around 376mm, right? Actually it is definitely not so much. From my measurements its effective focal length is about 210mm. This is strange. So maybe it was really modified somehow but it's hard to tell without side by side comparison or it is some special version of AE.


No, a 178mm lens is a 178mm lens regardless of what camera you put it on. It'll just act like a 178mm lens for that particular system. I.e., an 178mm Aero Ektar on a Hassie should look almost exactly like a Carl Zeiss 180mm Sonnar on a Hassie.


PostPosted: Sun Sep 18, 2011 4:04 am    Post subject: Reply with quote
Yes, 178mm should be 178mm

The other objection to yours being an Aero Ektar was that the barrel was too thin, compared with that of a different conversion to SLR mount. It seems to me that yours is just a more professional conversion. No doubt it is still a huge lens. The picture of it on the MF SLR is a little misleading. If you mounted it on your DSLR it would seem a monster.

As for f/2.2 - Since whoever did this conversion was highly skilled, is it possible that he managed to add a little more aperture to the lens ? The Aero Ektar could be like many other lenses which have an artificial restriction of the maximum aperture.


PostPosted: Sun Sep 18, 2011 10:24 am    Post subject: Reply with quote
luisalegria wrote:
As for f/2.2 - Since whoever did this conversion was highly skilled, is it possible that he managed to add a little more aperture to the lens ? The Aero Ektar could be like many other lenses which have an artificial restriction of the maximum aperture.


As Pentacon 4/300mm. Might be around F2.8 if removed?


PostPosted: Sun Sep 18, 2011 1:44 pm    Post subject: Reply with quote
rawhead wrote:
No, a 178mm lens is a 178mm lens regardless of what camera you put it on. It'll just act like a 178mm lens for that particular system. I.e., an 178mm Aero Ektar on a Hassie should look almost exactly like a Carl Zeiss 180mm Sonnar on a Hassie.


Yes, you're right. Sorry for the dumb question.

But in any case either my FOV calculations are incorrect or focal length was also increased to around 210mm.

luisalegria wrote:
As for f/2.2 - Since whoever did this conversion was highly skilled, is it possible that he managed to add a little more aperture to the lens ? The Aero Ektar could be like many other lenses which have an artificial restriction of the maximum aperture.


Where can I read more about such lenses?


Also I have several more pics.

Rear element (stop ring removed), focusing helicoid, focusing ring


Aperture and aperture ring


Focusing ring over helicoid


Front part put in place


Rear part of new housing (with my hassy adapter) put in place (don't pay attention to f/3.5 sticker, it's part of shutter speed scale for hassy)


So general idea is that AE is almost entirely inside new housing with only front element of original AE visible without disassembling.
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