APO RODAGON-D 75mm f4.5 2X opinions

ChrisR · Post by **ChrisR** » Sun Sep 25, 2011 1:39 am

That's interesting to see, Ray. All time-consuming stuff.
Wondering - Rodagon (iirc) say their lens is are optimal at f/5.6, and Schneider's best plot is at f/8.
I have found the Schneider to get better, more than half a stop from maximum.
I'm a bit surprised you don't routinely stack , these lenses are so good the normal C of C numbers are way out. DOF comes out under a tenth of a millimeter if you use C of C = width/2500.

ray_parkhurst · Post by **ray_parkhurst** » Sun Sep 25, 2011 7:01 am

Most of my coin imaging is at less than 1:1, so DOF with good resolution is acceptable without stacking. I do mostly US coins, which have pretty low relief. If I was doing ancients, I'd have to stack much of the time. I do need to make sure the coin is flat vs the sensor, though!

I visually checked each of these lenses to see which aperture was best at the center (where I was comparing), and each of them benefited from stopping down, but not too much. I saw degradation due to diffraction beyond f5.6 on all 3 of them, so chose to stay more open to let more light in.

My impetus for doing this was to see if I could come up with an alternative to my MZ7 for 3-5X, which is the required range for imaging of numismatic die varieties. So far the MZ7, while not the winner for image quality due to the relatively small aperture, is still the overall winner for convenience due to zoom flexibility and super long working distance. It's also a separate system so I don't have to do any conversions when going from full-coin imaging to high mag.

Here's the same coin with my MZ7 and Tucsen 3MP. The sensor on the tucsen is much smaller than my Nikon so the image looks more magnified. Single image, no stacking.

Bausch & Lomb MonoZoom7 at 3X

Bausch & Lomb MonoZoom7 100% crop of MM

crisarg · Post by **crisarg** » Sat Oct 08, 2011 10:53 am

Hello!

I've just received a copy of this lens. There is a slight creak in the barrel when holding it tighter than usual. Does anybody have the same experience with this? I also have a APO Rodagon N 50/2.8 with the same behaviour and a vanilla Rodaon 80/4.0 with no problem.

harisA · Post by **harisA** » Thu Oct 13, 2011 4:31 am

I also own the 75ARD1 version and i have some questions?

1)How can i mount it reversed to a m42 camera?

2)Whitch is the optimum distance from camera mount for 1x and 2x magnification (lens is consider reversed).

Thank you in advance

ray_parkhurst · Post by **ray_parkhurst** » Thu Oct 13, 2011 6:15 am

harisA wrote:I also own the 75ARD1 version and i have some questions?

1)How can i mount it reversed to a m42 camera?

2)Whitch is the optimum distance from camera mount for 1x and 2x magnification (lens is consider reversed).

Thank you in advance

I am not sure there will be any advantage to reversing the 75ARD1. I believe it is a symmetric design and thus is optically identical reversed. If you need to reverse it for mechanical reasons, it has 40.5mm front threads. I've never seen an M42-M40.5 reversing adapter, so you will need to "build" one out of available components. There is a guy on eBay who sells a set of adapters (I have no affiliation) that may work for you, though you can put together the components for M40.5 cheaper than buying the whole set:

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... SS:US:1123

Ray

harisA · Post by **harisA** » Thu Oct 13, 2011 11:02 am

ray_parkhurst wrote:
harisA wrote:I also own the 75ARD1 version and i have some questions?

1)How can i mount it reversed to a m42 camera?

2)Whitch is the optimum distance from camera mount for 1x and 2x magnification (lens is consider reversed).

Thank you in advance
I am not sure there will be any advantage to reversing the 75ARD1. I believe it is a symmetric design and thus is optically identical reversed. If you need to reverse it for mechanical reasons, it has 40.5mm front threads. I've never seen an M42-M40.5 reversing adapter, so you will need to "build" one out of available components. There is a guy on eBay who sells a set of adapters (I have no affiliation) that may work for you, though you can put together the components for M40.5 cheaper than buying the whole set:

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... SS:US:1123

Ray

Ray thank you for your answer.
Is it possible to answer my second question asuming that the lens is not reversed.
What is the back thread?

Thank you in advance

Haris.A

Pau · Post by **Pau** » Thu Oct 13, 2011 11:43 am

the mounting thread is M39 "Leica screw", the most standard in enlarger lenses