I was thinking of adding a 165mm f6.8 Rodenstock Eurynar to my collection.
its 4 elements in w grps, uncoated in a dial-set Compur shutter.
Anybody got an idea of coverage?
This is another sort of double anastigmat, though a different design to the Dagor.
I beleive that Goerz did something similar and called it a Celor?
If flare is going to be a real problem I won't bother.

yep it's a dialyte type, just like the Celor, artar and 203 ektar and lots of process anastigmats.

Use the longest lens shade possible, and you should be fine. Shooting Christmas lights at night might be a bit interesting though.

This is the same sort of design that Kodak used in one of the Ektar range. Was it the 203mm WF Ektar or the 178mm Aero Ektar?
I have seen the field of the type quoted as 60 degrees. How do you work out image circle from that figure (if its right)?

Quote:

On 2004-05-28 07:53, primus96 wrote: This is the same sort of design that Kodak used in one of the Ektar range. Was it the 203mm WF Ektar or the 178mm Aero Ektar? I have seen the field of the type quoted as 60 degrees. How do you work out image circle from that figure (if its right)?

Neither. The WF Ektars are 4 element wide angle double gauss types, two meniscus lenses on each side of the stop. The 178 Aero Ektar is quite complex, 7 elements, basically, iirc, a fast double gauss type.

The dialyte has four outer elements, two on each side of the stop. The outer two are biconvex, the inner two are biconcave.

Not that any of this lens design nonsense has much to do with how they shoot or whether to use a lens in a situation given that it covers the format and has the angle of view needed.

Again IIRC, the circle's diameter is focal length * tan(angle/2).

Cheers,

Dan

Quote:

On 2004-05-28 05:35, Les wrote: yep it's a dialyte type, just like the Celor, artar and 203 ektar and lots of process anastigmats. Use the longest lens shade possible, and you should be fine. Shooting Christmas lights at night might be a bit interesting though.

Les, the Vade Mecum is even more muddled than usual about Eurynars, but they say the f/6.3 Eurynaris a double anastigmat, i.e., sort of like the dread Dagor, and that some of the other Eurynars are dialyts.

Not that the design matters much, what's important is how well the lens in question shoots.

Cheers,

Dan

Regarding this particular Eurynar:
It may not have been intended for process use as its in a shutter not a 'barrel' lens.
How will the lens compare to the likes of a Dagor for:
Flatness of field.
Maintenance of sharpness at the edge of the coverage.
I am aware that a dialyte may have quite a narrow angle of view (47 degrees). This ones 165mm so surely it should cover 4x5.
This is 6" and a bit more and a 6" Cooke Aviar would do 6x4 (www.cookeoptics.com).

If Les can clarify that formula for working out image circle we might find it useful

I had a nice illustration but can't for the life of me figure out how to get it posted.

So you'll have to bare with me.

Imagine the lens on the left and two rays coming out to the right describing the angle of view.

Now draw a center line bisecting the angle of view.

Now we have a right triangle and some 9th grade trig ahead.

The Tangent of the half angle of view (trig teachers call "B" multipied by the focal length will give us.... well it gives us half of the image circle. So we multiply it by two to get the diameter

So Dan's half right. Take his formula and muliply by two.

Example: 165mm lens, 47° AOV

47°/2=23.5°

B= 165 * TAN23.5
B= 165 * 0.4348

B= 71.74mm

AOV=2*B= 143.4880mm

AOV= 5.65"

<font size=-1>[ This Message was edited by: Les on 2004-05-30 16:46 ]</font>

This sort of calculation is very useful, and is often done by people contemplating lenses they cannot afford, or that do not exist! Computers are a great improvement over the "trig tables" in the textbooks of my youth, and even over engineering calculators, in performing it.

Before Microsoft uncoupled "Windows" from "MS-DOS," a BASIC interpreter came bundled with the operating system. Alas, that is no longer so, but one still can purchase a BASIC language, if one didn't think to retain it when upgrading from the last "MD-DOS" version.

BASIC expects angles to be expressed in "radians," for some reason that must have seemed good to Kemeny and Kurtz. This is the only annoyance in writing little BASIC programs to do all sorts of lens and format calculations. You convert degrees to radians by multiplying the angle in degrees by pi/180; you convert radians to degrees by dividing the angle in radians by pi/180.

That hurdle past, here is a small BASIC routine that tells you the maximum frame diagonal when you know the angular coverage of the lens. It orginally was written in "TI Extended BASIC," then modified for "GW-BASIC." "QuickBasic" can run it, and doesn't need the line numbers:

100 REM *** Finds image circle when given angle of coverage ***
110 CLS : DEFDBL D, P
120 PI = 22 / 7: DRC = PI / 180 '*** Degrees-Radians Conversion
130 INPUT "Angle of coverage="; AD '***the Angle in Degrees
140 INPUT "Focal Length (millimeters)"; F
150 AHD = AD / 2 '*** Angle, Halved, in Degrees
160 AHR = AHD * DRC '*** that same semi-angle in Radians
170 THA = TAN(AHR) '*** the Tangent of that Half Angle
180 DH = F * THA: D = DH * 2 '*** DH is Half the Diameter
190 PRINT "Image circle (frame diagonal)="; USING "###.# mm."; D
200 PRINT USING "(or ###.## ins.)"; D / 25.4
210 END

Quote:

On 2004-05-30 19:48, t.r.sanford wrote: This sort of calculation is very useful, and is often done by people contemplating lenses they cannot afford, or that do not exist! Computers are a great improvement over the "trig tables" in the textbooks of my youth, and even over engineering calculators, in performing it. Before Microsoft uncoupled "Windows" from "MS-DOS," a BASIC interpreter came bundled with the operating system. Alas, that is no longer so, but one still can purchase a BASIC language, if one didn't think to retain it when upgrading from the last "MD-DOS" version. BASIC expects angles to be expressed in "radians," for some reason that must have seemed good to Kemeny and Kurtz. This is the only annoyance in writing little BASIC programs to do all sorts of lens and format calculations. You convert degrees to radians by multiplying the angle in degrees by pi/180; you convert radians to degrees by dividing the angle in radians by pi/180. That hurdle past, here is a small BASIC routine that tells you the maximum frame diagonal when you know the angular coverage of the lens. It orginally was written in "TI Extended BASIC," then modified for "GW-BASIC." "QuickBasic" can run it, and doesn't need the line numbers: 100 REM *** Finds image circle when given angle of coverage *** 110 CLS : DEFDBL D, P 120 PI = 22 / 7: DRC = PI / 180 '*** Degrees-Radians Conversion 130 INPUT "Angle of coverage="; AD '***the Angle in Degrees 140 INPUT "Focal Length (millimeters)"; F 150 AHD = AD / 2 '*** Angle, Halved, in Degrees 160 AHR = AHD * DRC '*** that same semi-angle in Radians 170 THA = TAN(AHR) '*** the Tangent of that Half Angle 180 DH = F * THA: D = DH * 2 '*** DH is Half the Diameter 190 PRINT "Image circle (frame diagonal)="; USING "###.# mm."; D 200 PRINT USING "(or ###.## ins.)"; D / 25.4 210 END

TR, Excel has trig functions too ...

Cheers,

Dan

That is good to know. Does it come with a well-written manual? If it does, it's a first for Microsoft!

I'll stick to my K&E slide rule thanks. No batteries, no upgrades, no bugs.

...I ever could figure out where to put the decimal points!

Can anyone give us any help on writing the functions so this works on a Excel spreadsheet?
I can do it on a calculator, but the problem seems to be in getting the tangent of the half angle.
I tried the formula on a reuular calculator and got a image circle of 143mm for this lens - way too small for 4x5.
Thus I was releived to be outbid.

Quote:

On 2004-06-01 04:53, primus96 wrote: Can anyone give us any help on writing the functions so this works on a Excel spreadsheet?

Coverage?

Coverage = tan (angle/2)*focal length*2

Stick the angle in one cell. Focal length in a second one.

Quote:

On 2004-06-01 04:53, primus96 wrote: Can anyone give us any help on writing the functions so this works on a Excel spreadsheet? I can do it on a calculator, but the problem seems to be in getting the tangent of the half angle. I tried the formula on a reuular calculator and got a image circle of 143mm for this lens - way too small for 4x5. Thus I was releived to be outbid.

This was very interesting and fit right in with my "AngleOfView" spreadsheet, so I added it. It's available in either Lotus 123 or excel format. I can't test the excel one because I don't use ms products! But it imports back into 123 correctly...
It's available at:
http://www.southbristolviews.com
on the left side menu, select "LF lens equivalents"...

And remember, spreadsheet calculate in radians, not degrees!