Search found 3415 matches

by ray_parkhurst
Mon May 09, 2016 12:54 am
Forum: Equipment Discussions
Topic: Calculating effective aperture with teleconverter
Replies: 2
Views: 1789

Rik...thanks for confirming. The working distance factor nicely explains it...Ray
by ray_parkhurst
Sun May 08, 2016 8:58 pm
Forum: Equipment Discussions
Topic: Calculating effective aperture with teleconverter
Replies: 2
Views: 1789

Calculating effective aperture with teleconverter

I want to make sure I am calculating effective aperture correctly for a lens used with a teleconverter. I think the calculation should be made in order from object to sensor, looking at the objective lens + extension as a black box that the teleconverter acts upon, rather than looking at the whole s...
by ray_parkhurst
Sat Apr 30, 2016 7:53 am
Forum: Equipment Discussions
Topic: 80mm lens shootout - for coin photography
Replies: 48
Views: 19226

I ended up picking up a copy of this lens from eBay UK. Thanks for the link AK. I'll add it to my test group. My shootout is moving along very slowly so there is time to add it.
by ray_parkhurst
Thu Apr 28, 2016 6:02 am
Forum: Equipment Discussions
Topic: 80mm lens shootout - for coin photography
Replies: 48
Views: 19226

may be a little late.... Have you looked at the Agfa 80/4 repromaster? No, I've never owned an Agfa lens. Checking eBay I see a 80/4.5 Repromaster: http://www.ebay.com/itm/Agfa-80mm-1-4-5-repromaster-/351678686256?hash=item51e1aee430:g:cMwAAOSwu1VW6DbF The mount on this one seems quite roughly-done...
by ray_parkhurst
Fri Apr 15, 2016 10:36 am
Forum: Equipment Discussions
Topic: Cheep Cinese 20X objective.
Replies: 7
Views: 1332

Looks like 29.1mm is diameter of knurled part, not the thread.
by ray_parkhurst
Sun Apr 03, 2016 6:14 pm
Forum: Equipment Discussions
Topic: Your fav lens(es) for low-power magnification studio work
Replies: 40
Views: 5555

Saul wrote:
ray_parkhurst wrote:105mm Rodenstock LFOV lens.
Hi Ray,

Can you give more details about this lens ? I found Rodenstock 108mm LFOV , 110mm LFOV , not sure are they the same you tested ?

Thanks,

Sorry, typo. Not 105mm, but 108mm.
by ray_parkhurst
Fri Apr 01, 2016 6:29 pm
Forum: Equipment Discussions
Topic: Your fav lens(es) for low-power magnification studio work
Replies: 40
Views: 5555

I have not tested a M-Componon 80/4, though I did look for one at a reasonable price when I was sourcing lenses for my 80mm shootout and could not find one I wanted to take a chance with. I did own a 90ACHM a while back, and while a reasonably capable lens, it fell short of what I could achieve with...
by ray_parkhurst
Fri Apr 01, 2016 8:15 am
Forum: Equipment Discussions
Topic: Your fav lens(es) for low-power magnification studio work
Replies: 40
Views: 5555

I have more than one of some of these, perhaps I should go to LA (Lenses Anonymous). Copies can vary, so deductions are unreliable. But show me a picture, printed A3, from many of the lenses we've discussed here, and I doubt I'd be able to tell which lens took it. I might guess at which ones didn't...
by ray_parkhurst
Thu Mar 31, 2016 8:31 pm
Forum: Equipment Discussions
Topic: Your fav lens(es) for low-power magnification studio work
Replies: 40
Views: 5555

Agreed. The Olympus macro lenses make a nice set, but the 80mm is beatable. It's about half the price of the Rodagon Ds, though, and you get a helicoid. Olympus to Nikon isn't the easiest fit, to arrange. .... The bellows I use is the Canon Auto Bellows FD, so when I purchased the 80OM for the shoo...
by ray_parkhurst
Thu Mar 31, 2016 6:04 pm
Forum: Equipment Discussions
Topic: Your fav lens(es) for low-power magnification studio work
Replies: 40
Views: 5555

Btw, another lens I have in mind and haven't tried yet is the Zuiko 80/4 Auto Macro, not too expensive, I've heard good things about it and perfectly fits my needs. How about this one? I purchased an OM 80/4 bellows lens based on good reviews and it is part of an 80mm shootout that I am (slowly) pu...
by ray_parkhurst
Thu Mar 31, 2016 7:34 am
Forum: Equipment Discussions
Topic: Your fav lens(es) for low-power magnification studio work
Replies: 40
Views: 5555

I've tested many, many lenses in this mag range and have settled on a few that I use regularly. I say "use regularly" because I occasionally choose others for particular purposes, but not for everyday use, either because they are harder to use (odd mounts, etc) or they are just too expensive and rar...
by ray_parkhurst
Tue Mar 22, 2016 6:54 am
Forum: Equipment Discussions
Topic: Kohzu or Thorlabs goniometers
Replies: 7
Views: 1395

boomblurt wrote:I have a matched pair of (2nd hand) 40mm OptoSigma goniometers with centre of rotation 35mm above the top - quite smooth and adequate.
Your OptoSigma's are probably the same as my Sigma Koki's. Very nice to work with, and small.
by ray_parkhurst
Mon Mar 21, 2016 1:45 pm
Forum: Equipment Discussions
Topic: Moving specimen rather than moving camera
Replies: 5
Views: 1074

I don't use a StackShot (I use a different stepper system) but I do move the subject instead of the camera. Other than the lighting issue, it seems like moving the smaller mass of the subject rather than the large mass of the camera and lens system seems like an advantage for vibration, settling tim...
by ray_parkhurst
Wed Mar 16, 2016 10:51 am
Forum: Equipment Discussions
Topic: Small metal knobs for manual stages
Replies: 22
Views: 3937

Thanks for the link.

The knob arrived yesterday. Will hopefully have time over the weekend to go through install process.

Thanks!

Ray
by ray_parkhurst
Wed Mar 16, 2016 3:29 am
Forum: Equipment Discussions
Topic: Small metal knobs for manual stages
Replies: 22
Views: 3937

Thanks g4lab, I had tried DigiKey and Mouser with little luck, but not Newark. They do have a couple options...Ray