Rodenstock Rodagon 150mm f/5.6 rear diamater?

Have questions about the equipment used for macro- or micro- photography? Post those questions in this forum.

Moderators: rjlittlefield, ChrisR, Chris S., Pau

RobertOToole
Posts: 2627
Joined: Thu Jan 17, 2013 9:34 pm
Location: United States
Contact:

Post by RobertOToole »

Chris S. wrote:
RobertOToole wrote:When you pull down a lens with short focus you can pull some lenses down quite a bit but all will eventually suffer IQ loss in the corners. I think this might happen sooner than later with a high-NA lens.
Robert, I was thinking more about spherical aberration and perhaps other issues. There was a post on the topic of using converging lenses at focus points other than infinity. I can't find it right now, and am pretty sure it was written by Rik. The post referenced this graphic. While the data in the graphic were compiled by varying tube length with finite objectives, my recollection is that we should expect similar results when varying converging lens focus with infinite objectives. The upshot was that with low NA objectives, we can get away with considerable change in tube length (or focus of a converging lens). But as the NA of the objective goes up, tolerance of this change goes down.

I'm interested in this because on my rig, with its Mitutoyo MT-1 tube lens, I've shortened focus by 2-3mm to eliminate a variable-length tube that wasn't as robust as I like. I regularly work with a Mitutoyo 100x/0.70 objective, and have never seen any obvious degradation. An NA 0.75 objective that I tested also behaved splendidly. But I wonder, at those larger NA's, if I'm leaving some smidgeon of quality behind. I don't have an easy way to test. . . .

--Chris S.

This took more time than I expected!

A6300
Century +4 tube lens
(BTW the FL is not really 250mm, more like 230mm, Schneider reported that is normal and within specs)
Infinity focus
Forward/normal mount
75mm tube between TL and Obj.
Mitutoyo M Plan 100x 0.7

Un-cropped and resized to 1500px
Single frame
Flash x 4

Infinity focus

Image

-5mm extension

Image

-10mm extension

Image

-15mm extension

Image

Results? They all look equally bad :shock:

So I would say with these results that short focus here did not improve sharpness at least.

Going from 230mm to 215mm did not show much effect (sharpness loss or improvement). Larger % steps going from 200mm to 130mm maybe should have a much more noticeable effect I would expect.

Not much else to say except that this test reminded me that its not easy or fun to shoot at 100x!

Note: Looks like I must have bumped the wafer, the target shifted between first and 2nd frames!

Best,

Robert

Chris S.
Site Admin
Posts: 4042
Joined: Sun Apr 05, 2009 9:55 pm
Location: Ohio, USA

Post by Chris S. »

Robert, thanks a bunch! Sorry this test was so much trouble.

I layered your images in Photoshop, and flashing between, I think I do see degradation increasing step-wise with each move away from infinity focus. Granted, there are confounding details--single shots vs stacks, and subject bumping as you described.

I’m discomfited enough by your results to plan re-check my tube lens assembly, despite my reluctance to perform surgery on a working system.

So I think that all the trouble you took has real value in addressing this question. Your time may have been spent unpleasantly, but I think it was spent usefully.
Not much else to say except that this test reminded me that its not easy or fun to shoot at 100x!
The great thing about shooting at 100x is that when you go back to shooting at 10x, 20x, or 50x, it seems so easy and fun!

If you bought your objective used, I wonder if you were sold a bad copy. Or perhaps the wafer just isn’t a good test subject for this magnification and NA? If you'd like me to test your objective against mine (which I've tested against others, so I know it's good), feel free to send your objective my way, and I’ll happily return the favor of the time you spent on this test for me.

--Chris
Last edited by Chris S. on Tue Mar 03, 2020 12:03 am, edited 1 time in total.

RobertOToole
Posts: 2627
Joined: Thu Jan 17, 2013 9:34 pm
Location: United States
Contact:

Post by RobertOToole »

Glad to help Chris.

Yes, the 100x was purchased used. Also I agree that the IQ is probably not what it could be.

This is the last lens from a full set I had at one point, actually a set of M Plans and BD Plans. I found a 50x M Plan with a chipped front element for $50 on eBay so I bought it for a project for my site and what happens? The chipped 50x tested to be much better than my mint 50x. Turns out most of my Mitutoyos were that way. I had multiple 20x M Plans, they were all "off". So I had no choice but to sell every lens with only the 100x left.

The 20x M Plans were particularly prone to bad inner element condition for some reason. I will never buy another used Mitutoyo objective, only new.

So slowly, even more slowly now this year with the c-virus crisis, I plan to buy the 5x, 7.5x, 10x, 20x new from the Mitutoyo distributor in Japan. So far I have the 5x and 10x.

This Feb I planned to pick up a new 7,5x when I was in Japan in Feb, but so far 2020 has been a disaster with 12 tour cancellations since Jan. resulting in a $40K loss for my business (net profit, not income, the gross income number is a lot worse!)!

Hopefully the virus situation gets better soon. My friends in Japan tell me a huge chunk of businesses are going to go under in Japan, Korea, and China, small businesses are already missing loan payments and its only March. The government and banks are panicking, especially in Hokkaido.

Best,

Robert

RobertOToole
Posts: 2627
Joined: Thu Jan 17, 2013 9:34 pm
Location: United States
Contact:

Post by RobertOToole »

Just saw this article after I hit submit.

Imagine all the small businesses impacted if Canon is impacted, there will be big ripples in the industry.

Image

Chris S.
Site Admin
Posts: 4042
Joined: Sun Apr 05, 2009 9:55 pm
Location: Ohio, USA

Post by Chris S. »

RobertOToole wrote:I will never buy another used Mitutoyo objective, only new.
When I bought my set of Mitutoyo objectives (none new), I must have been very lucky. I returned only one, which looked as if it had been shot blasted. All the others were great, which I can say with confidence as each has been tested against multiple samples belonging to other people. Lately, in particular, I've been seeing a spate of bad ones come up in testing.
RobertOToole wrote:. . .so far 2020 has been a disaster with 12 tour cancellations since Jan. resulting in a $40K loss for my business (net profit, not income, the gross income number is a lot worse!)!

Hopefully the virus situation gets better soon. My friends in Japan tell me a huge chunk of businesses are going to go under in Japan, Korea, and China, small businesses are already missing loan payments and its only March. The government and banks are panicking, especially in Hokkaido.
Ugh, I'm sorry to hear about the impact on your business. Of course you'd be among the first to feel what I agree is likely to be a major economic disruption.

I certainly can't blame your clients for cancelling. I said no to a couple of wonderful trips in March and April, because I don't want to be getting on airplanes any time soon.

--Chris S.

RobertOToole
Posts: 2627
Joined: Thu Jan 17, 2013 9:34 pm
Location: United States
Contact:

Post by RobertOToole »

Chris S. wrote: When I bought my set of Mitutoyo objectives (none new), I must have been very lucky. I returned only one, which looked as if it had been shot blasted. All the others were great, which I can say with confidence as each has been tested against multiple samples belonging to other people. Lately, in particular, I've been seeing a spate of bad ones come up in testing.
I blame all of my inconsistency issues on the sellers.

-3 or 4 objectives show up from China (from Taobao sellers) wrapped in newspaper, no foam or bubblewrap in a reused box.

-An East coast eBay seller ships a Mitutoyo FS-60 scope + objective set in a single walled cardboard box, so the box fails apart soon after pickup, the USP man flips the box over upside down so things wouldn't fall out of the holes. The XY stage was held in place by gravity so that falls onto the scope and then it travels 2000 miles to California upside down. At least they removed the Mity micrometers from the stage but they were placed loose into the box so those were throwaways when they made it to LA. This is after I asked to pay more $ for a professional crate and shipping. I sold all the objectives :shock:
Ugh, I'm sorry to hear about the impact on your business. Of course you'd be among the first to feel what I agree is likely to be a major economic disruption.

I certainly can't blame your clients for cancelling. I said no to a couple of wonderful trips in March and April, because I don't want to be getting on airplanes any time soon.


I don't blame my clients at all, it's their choice of course, but cancelling within 90 days of the date = zero refund from me.

If I did the same thing and cancelled the tour 2 months from the start and basing it on some breaking news they would sue me.

People starting cancelling in January when it was still mostly contained in China. I've been through SARS in 2004 and the H1N1 in 2009 and both were a similar situations, people went into full panic mode and in the end the normal flu was 10,000x worse.

This is different of course and it seems to be worse than SARS and H1N1.

Received two more cancellations last night. :(

Best,

Robert

Post Reply Previous topicNext topic