Ilex Acuton 150mm f4.8 Looking for Info

[Jan Pedersen]

There's not much information on the Ilex Acuton lenses but i do have some on the 215 4.8 of which i have one. There's a little on the 180 but, nothing as far as i can tell on the 150 4.8
It is as the 215 a convertible.

Anybody know something about the 150 and how they perform?

Thanks.

[David Lindquist]

I have no personal experience with this lens. I do have some circa 1970's (late 70's?) Ilex literature that says the combined lens covers an 8.2 inch diameter circle and the single cell covers an 8.6 inch diameter circle. Ilex seems to have had a rather ambitious lens program which included the convertible f/4.8 Acuton in three focal lengths and the and the wide angle f/8 Acugon (essentially the same design as the f/8 Super Angulon) in a 47, 65 and 90mm version as well as their four element f/6.3 Acutar in seven focal lengths.No mention is made that they were multicoated so I expect they weren't.
David

[Jan Pedersen]

Thanks David.
The 215 Acuton is coated but it may be just a single coating. I don't have the 150 in hand yet so i can't tell.
I suspect that the 6.3 Acutars are the same as the Calumet Caltars they are also coated but again maybe only a single coating.
Was hoping that the 150 would cover 5x7 but can see that 8.2" is going to be a little tight.
The Ilex litterature you have is that something that was made public in book or magazine format?
Thanks again.

[Dan Fromm]

Jan, Acutars are tessar types, Acutons are 6/4 convertible plasmat types, and Acugons are f/8 Super Angulon types.

[Jan Pedersen]

Dan, Thank you for clarifying that, that was also my impression at least on the Acutars/Caltars with the exception of the 508/7 which is a triplet but i am not sure that one was made in the Acutar series.
Thanks.

[Mark Sawyer]

Thanks David.
Was hoping that the 150 would cover 5x7 but can see that 8.2" is going to be a little tight...

Don't give up on it without trying it. Ilex listed coverage for the 215mm f/4.8 Acuton as 307mm, but mine covers the 312mm of 8x10 with a bit left over for movements, and is still quite sharp at the corners. One of my favorites lenses, I think it matches my 210mm gold-rimmed Dagor.

[Jan Pedersen]

Mark, No plans giving up on either the 215 or the 150 they were so inexpensive.
The 150 is even in a Copal 1
Have yet to compare the 215 directly with my 210 Dagor (coated but no gold) i think the Acuton covers a little more.

[David Lindquist]

Thanks David.

The Ilex litterature you have is that something that was made public in book or magazine format?
Thanks again.

This is a brochure I picked up somewhere, reasonably sure it was no later than the late 70's. Unfortunately it has no date code. Burke & James is indicated to be the distributor of these lenses. It lists their seven Acutars as being available in these focal lengths: 6 1/2, 7 1/2, 8 1/2, 10, 12, 14 3/4 and 20 inches. The 20 inch had a maximum aperture of f/7. The other six a maximum aperture of f/6.3. These focal lengths and maximum apertures are the same as what is described for the Caltar lens series in my 1968 Calumet catalogue. (Note though that Calumet did not list a 7 1/2 inch Caltar.) Regarding the 20 inch Caltar being a triplet, I remember reading that before but don't remember where. In my 1968 Calumet catalogue the blurb describing the six Caltar lenses (6 1/2 - 20 inch focal lengths) includes the sentence "The circle of coverage in these four (emphasis added) element lenses is less than the Series-S Caltar." And the blurb in my Ilex "Acu-Series" brochure for the Acutars shows the diagram of a Tessar (but no further description of the lens design). Having said that, I wouldn't be surprised to find the 20 inch lens was in fact a triplet and that this fact didn't make it in to the catalogue copy of either vendor.
David

[Jan Pedersen]

Regarding the 20 inch Caltar being a triplet, I remember reading that before but don't remember where.
Could have been the conversation Mr. H. Lynn Jones had on the Ilford Forum.
http://www.ilfordphoto.com/photocommunity/forums/theforum/topic.asp?TOPIC_ID=7641
Great lens but big.
Jan

[David Lindquist]

Found where I read this. It was in Kerry Thalmann's excellent history of the Caltar lenses in the May/June 2003 issue of View Camera. Quoting from that article:

"The final Ilex-Caltar offering, the 20-inch f/7.0 Caltar is a bit of an enigma. The Calumet Catalogs fom 1968-1976 group this lens with the 4/3 Caltars, but Lynn Jones, who worked at Calumet at the time has stated this lens is a three element design with a usable coverage of only about 35 degrees- although the circle of illumination is substantially larger (equal to about 45 degree coverage). This is far less than the 64 degrees of the four element Caltars. I have not personally used this lens and, therefore, cannot verify this claim. This 20-inch f/7.0 Caltar was intended to be used as a long focal length lens on the 8x10 format. It was not meant to cover the larger 11x14 or banquet formats."

Note that the 20 inch f/7 Acutar is described in the line listing of the Acutar lenses in my Ilex brochure as having an angle of view of 58 degrees (aperture not specified) and covering a maximum film size of 11x14 inches. Incidentally the 14 3/4 inch Acutar is also said to cover a maximum film size of 11x14 inches. My 1968 Calumet catalogue in its blurb accompanying their six Caltars (including the 20 inch) says they cover an angle of 56 degrees wide open and 64 degrees "as the lens is stopped down" (stopped down to what is not given).
David

[Jan Pedersen]

David, Thanks a lot for this additional information about the 20"
Somewhere i read that the first examples were soso but later they were excelent lenses. Well i was counting reflections last night and to me it looks like it is a Tessar not a Triplet. Comparing to the 375 reflections are identical.
Perhaps that explains the difference from the first to the later versions? My 20" has a high serial number. I do however not know how to count reflections from a triplet so i need some assistance here.
Thanks.

[Chauncey Walden]

Jan, I would think that Tessar would have an additional weak reflection from the cemented interface of the third and fourth elements.

[Jan Pedersen]

Chauncey, there is one very weak reflection behind the 4 strong reflections and it seems to be the same in the 375mm.
How does reflections from a triplet look like?

[Dan Fromm]

Four strong reflections in front of the diaphragm, two behind. No weak reflections on either side of the diaphragm.

[Jan Pedersen]

Thanks Dan. Still not fully convinced that there is a weak reflection in the front but there is one in the rear, and a strong.
So, the lens must have changed design along the way or it was never a triplet from the beginning.

[Dan Fromm]

Jan, a normal tessar type will have four strong, no weak, reflections in front of the diaphragm and two strong, one weak, reflections behind the diaphragm. The weak reflection can be hard to see.

To help you think about reflections and counting them, a glass-air interface makes a strong reflection, a glass-cement-glass interface makes a weak one. For example, a dagor type is a pair of cemented triplets, so will have two strong and two weak reflections on each side of the diaphragm. I can't say it too strongly, weak reflections can be very hard to see.

I said "normal tessar type" because there are tessar types that are reversed, i.e., that have the cemented doublet in front of the diaphragm and the pair of singlets behind it. Most are macro lenses. Examples: 90/6.3 CZJ M or Mikrotar (sold engraved M or Mikrotar), 100/6.3 Reichert Neupolar, B&L Micro Tessars.

[Jan Pedersen]

Thanks again Dan. It is now almost a daily ritual that i find a little maglite and my big old lenses but i had to find out what it is i have to play with.
My darkcloth was helping getting the right black behind the lens group, shutter is to reflective.
The front has 4 strong and 1 weak and the back two strong and one weak, one of the strong very large so i am thinking that is just a reflection from the outside rear element?
It is the exact same patern from the 375mm.

[Dan Fromm]

Jan, when I'm trying to count reflections I close the diaphragm. If I'm really puzzled and really want to know, I unscrew the cells from their barrel/shutter and look at them one at a time.

[Jan Pedersen]

Dan, That was exactly what i had to do to find that weak reflection in the front.
It does not seem to be a normal Tessar then since it also has a weak reflection between the two strong in the rear cell.