The need for speed! Aero-Ektar

[John Kasaian]

:eek: It was between a Dallmeyer Pentac and an Aero Ektar on the field of ebay honor and the Aero Ektar won---or rather I won the Aero Ektar as the Pentac blew right out of my budget. My interest in these lenses is for night photography using a 5x7 camera (an Agfa-Ansco Universal) Any barrel lens for under $40 isn't too bad a deal I figure, and I've got a lensboard with a big honkin' hole the beast may or may not fit.I suppose I'll have to make a concrete and lead box to keep it in (or do I need a permit from the nuclear regulatory conmmission?) but aside for being a fast lens and perhaps loosing a few stops due to staining from the effects of hot glass (though this one sems pretty clear from the pictures---I've seen some that look like the color of tea) I don't really know much about the things. My main concern is will it illuminate a 5x7 gg? I know they were designed to cover 5x5, but do they have mechanical vignetting to limit coverage? I'm not too concerned about the corners being mushy. Any thoughts? Ideas? Suggestions?

[Frank Petronio]

I usually made aperture adjustments by holding the lens between my thighs. It was fine. And kids with three arms make great assistants.

I don't know about the coverage. IMHO the only reason to use it was at f/2.5, it didn't do that great stopped down, it just seemed muddy. So wide open the coverage may not be that... large.

[domenico Foschi]

Frank, holding such a lens between your thighs seems to me an unncessary risk.:D

[Per Madsen]

Frank, holding such a lens between your thighs seems to me an unncessary risk.:D

The Thorium glas in the lens is an Alpha emitter.

You have to eat the lens to get any significant radiation damage.

Goggle for "Thorotrast" for an example of Thorium used as a contrast
medium for brain blood vessel examinations with long term consequenses.

http://en.wikipedia.org/wiki/Thorotrast

[John Kasaian]

The Thorium glas in the lens is an Alpha emitter.

You have to eat the lens to get any significant radiation damage.

Goggle for "Thorotrast" for an example of Thorium used as a contrast
medium for brain blood vessel examinations with long term consequenses.

http://en.wikipedia.org/wiki/Thorotrast

The blood vessels in my brain could probably use the help!;)

[Struan Gray]

The Thorium glas in the lens is an Alpha emitter.

You have to eat the lens to get any significant radiation damage.


It's the gamma from the daughter products that you need to worry about. Michael Briggs is the man to read:

http://home.earthlink.net/~michaelbriggs/aeroektar/aeroektar.html

[Carsten Wolff]

I second Struan's suggestion. I've still got a 7" Aero Ektar; it reads 100 counts/sec through the back..... it's not going anywhere near my face even via a GG..... you may argue only a dosimeter gives you a porper idea; that'll be the next step.
Get HP5 instead. :)

[Michael Heald]

Hello! I pl.ayed with an Aero Ektar for a while for 4x5 astrophotography. It covered at f2.5 without any problem, but I'm not sure about 5x7.
The main problem I had was with chromatic aberration. I spent a lot of time testing it and to get pinpoint star images, I had to stop down to f5.6. Best regards.

Mike

[Michael Heald]

Hello! I forgot to mention that the yellow tends to clear when you point it at the sun for a while. Of course, don't leave it out when the sprinkler comes on like I did. It tends to ruin all the hard work put in to make the lens better!

Mike

[Per Madsen]

It's the gamma from the daughter products that you need to worry about. Michael Briggs is the man to read:

http://home.earthlink.net/~michaelbriggs/aeroektar/aeroektar.html

I forgot about the daugther products.

What is the normal decay chain for Thorium ?

[Struan Gray]

http://en.wikipedia.org/wiki/Decay_chain

Or, if you like pictures:

http://www.chemsoc.org/networks/learnnet/data/ds_radioactive_decay_1.htm

Various thorium isotopes crop up in the decay chains of other radioactive elements (you can see them in the Radium and Actinium chains at Wikipedia), but the thorium in lenses is the long-lived, and hence naturally ocurring isotope Th-232.

I have a 7" Aero Ektar. I would happily use it, if I had a need. I think I once worked out that when focussed at infinity it would irradiate me at the (conservative) level allowed for occupational radiation workers here in Sweden. It is actually more of a hazard when packed away in a rucksack against my back. That said, I keep it in a far corner of the basement, and don't let my kids play with it, despite it being an excellent fire-starter.

One thing that would be interesting would be to see if the optical performance changed on bleaching the colour centres. It should do, but whether the amount is measureable I don't know.

[Walter Calahan]

Wow, thank goodness I don't have any daughters, but I do have three of these lenses.

I think I'm going to store them far, far away when not in use.

[Joseph O'Neil]

I have one of these lenses, couple of thoughts..

1) they will cover 4x5 no problemo, but 5x7 - I doubt it;

2) yes, the last TWO rear elements are the radioactive ones. They sure do make my Medcom 4 monitor chirp like a songbird on steriods. :)

3) These are early AERIAL camera lenses - ego - they are designed for extended red colour correction. Most B&W, aerial camera film - even into recent times, are eitehr red extended - like the old tech pan, or into the near IR - kinda like some of the "traffic films" of today like Ilford SF , which I think went to 720 to 740nm? I am not sure if they even make the stuff anymore. They would of also used early infra-red films too, but i do not know how sensitive those film were.

Anyhow, the point is, these lenses were almost always sold or equipped with yellow and red filters (I think surplus shack still sells those filters). Point being - they were not designed, IMO, to have great focusing at the blue end of the spectrum.

I think, based on the very few samples I have seen, and the one I own, if you are shooting B&W film, and you always use the yellow filter at the very least, you'll get decent results. But sans filter, or for colour film, probally not so great.

joe

[GPS]

:.. I know they were designed to cover 5x5, but do they have mechanical vignetting to limit coverage? ...

Just to answer your question - there is no inbuilt mechanical obstacle to limit the coverage, if your question means this. They were build to cover the current aerial film format.

[John Kasaian]

I second Struan's suggestion. I've still got a 7" Aero Ektar; it reads 100 counts/sec through the back..... it's not going anywhere near my face even via a GG..... you may argue only a dosimeter gives you a porper idea; that'll be the next step.
Get HP5 instead. :)

I'll be shooting HP-5+! Speed and more speed! Weeeeee!:cool:

Perhaps I'd better run this baby past the nuclear medicine lab at the hospital where I sometimes work. :eek:

[Hollis]

Does anyone know if the 12" aero ektar will cover 8x10 wide open? Does anyone have an image made with this lens on 8x10? Please, let me know. I think the thorium is getting to me, I seem to be buying obsolete lenses with reckless abanon.

Hollis
www.hollisbennett.com