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1. ## Thread: Calculating f-stop progression . . .how are the numbers derived?

by Nodda Duma
Replies
9
Views
239

### Re: Calculating f-stop progression . . .how are the numbers derived?

As Havoc notes, f/# values change by the area size. As such, the numbers change by the square root if 2.
2. ## Thread: SP-445 agitation test results challenging

by Nodda Duma
Replies
12
Views
416

### Re: SP-445 agitation test results challenging

As an optical engineer who has tested non-uniformity of imaging systems many times over my career, my first and primary suspect is the actual setup of the test described: I.e. Sheets of regular...
3. ## Thread: Wet/dry plate holders for 4x5

by Nodda Duma
Replies
13
Views
3,744

### Re: Wet/dry plate holders for 4x5

The ChromaGraphica double dry plate holders are NOT 3D printed. They are modern, injection molded assemblies, designed by photographers who are also engineering professionals.

Will fit 4” x 5”...
4. ## Thread: getting glass CLEAN, how do you do it?

by Nodda Duma
Replies
40
Views
1,289

### Re: getting glass CLEAN, how do you do it?

Makes sense.. essentially glass enjoys a nice cleaning in a mildly alkaline solution, which is what you’ll get with that.
5. ## Thread: getting glass CLEAN, how do you do it?

by Nodda Duma
Replies
40
Views
1,289

### Re: getting glass CLEAN, how do you do it?

I don’t know any optical shops which use that. Too time-consuming for production to “touch” each lens. For large quantity optics, glass washing machines using distilled water and a purpose-made...
6. ## Thread: Storage of Exposed/developed glass plates?

by Nodda Duma
Replies
18
Views
499

### Re: Storage of Exposed/developed glass plates?

Drew, I did some homework before recommending storage methods for dry plates (my recommendations are never arbitrary. :) ). The dry plate boxes and envelopes sold through Gaylord (and a couple other...
7. ## Thread: Uneven Development -- 5X7's in Stearman Press 8X10 Tray

by Nodda Duma
Replies
24
Views
1,379

### Re: Uneven Development -- 5X7's in Stearman Press 8X10 Tray

Did you try picking it up *completely off the countertop* and rocking it around? This and 500ml of developer works for me with B&W, C-41, E-6, etc. It’s the same equipment as yours, so it’s fair...
8. ## Thread: Night Vision for focusing?

by Nodda Duma
Replies
13
Views
555

### Re: Night Vision for focusing?

As an optical engineer who is familiar with the hazards of lasers, I would advise *against* viewing the focused image of a laser spot with the type of magnification used for viewing the ground glass....
9. ## Thread: Correcting Focus When Stacking Filters

by Nodda Duma
Replies
16
Views
874

### Re: Correcting Focus When Stacking Filters

Jim Noel is spot on. Theoretically, filters should contribute no optical power and therefore would not affect the image. In the real world, consumer-grade filters do have an impact... not focus per...
10. ## Thread: Tilt an old lens a teeny bit off axis to improve image. Anyone ever heard of this?

by Nodda Duma
Replies
13
Views
653

### Re: Tilt an old lens a teeny bit off axis to improve image. Anyone ever heard of this

Yes, actually, because you cannot ignore alignment errors. Perfect alignment only exists on paper. Real, manufactured lenses are not ideal and have associated tolerances they have to meet to ensure...
11. ## Thread: Tilt an old lens a teeny bit off axis to improve image. Anyone ever heard of this?

by Nodda Duma
Replies
13
Views
653

### Re: Tilt an old lens a teeny bit off axis to improve image. Anyone ever heard of this

Stopped down, I agree that there may be benefit, knowing what I know of stray light and ghosting. So yes, you could be on to something.

At very small apertures light rays are intersecting...
12. ## Thread: Researching Eastman Dry Plate & Film Co. 5x7 Camera & Need Help

by Nodda Duma
Replies
2
Views
252

### Re: Researching Eastman Dry Plate & Film Co. 5x7 Camera & Need Help

Hey Tim,

I’m 85% sure that Eastman set the standard dimensions for holders in large part by buying up other companies and making them convert to the Kodak standard sizing. If standard 5x7 holder...
13. ## Thread: One way to fix lens separation

by Nodda Duma
Replies
44
Views
39,993

### Re: One way to fix lens separation

Hey Steven,

It’s due to the newly formed airgap. The index difference between adhesive and glass is not significant enough to form visible Newton rings.

-Jason
14. ## Thread: Diffraction. When does it really matter with LF?

by Nodda Duma
Replies
84
Views
3,309

### Re: Diffraction. When does it really matter with LF?

Yes, they are wavelength-dependent geometric effects.

Sphero-chromatism: focus vs wavelength
Lateral color: Distortion vs wavelength

Fun fact: Focus is considered an aberration... the...
15. ## Thread: Diffraction. When does it really matter with LF?

by Nodda Duma
Replies
84
Views
3,309

### Re: Diffraction. When does it really matter with LF?

All of the basic, third order Seidel aberrations can and have been corrected completely. The Cooke Triplet does that. Higher order / residual aberrations, however...
16. ## Thread: Diffraction. When does it really matter with LF?

by Nodda Duma
Replies
84
Views
3,309

### Re: Diffraction. When does it really matter with LF?

Drew... LOL. I just.... What you saw was the effect of turbulence, integrated over the exposure time of your camera and the response time of your eye. :D

Diffractive effects over a mountain...
17. ## Thread: Diffraction. When does it really matter with LF?

by Nodda Duma
Replies
84
Views
3,309

### Re: Diffraction. When does it really matter with LF?

Because it is not a geometric effect.
18. ## Thread: One way to fix lens separation

by Nodda Duma
Replies
44
Views
39,993

### Re: One way to fix lens separation

Agree on all accounts..though the concoction is straight from Norland and my experience in the optical shop doing this is a bit different than yours (if you do the math, you find it’s only 0.78%...
19. ## Thread: One way to fix lens separation

by Nodda Duma
Replies
44
Views
39,993

### Re: One way to fix lens separation

Obviously works in a pinch, but a more robust method:

100 parts Methylene chloride. 15 parts methanol, and 3 parts ammonia (26% conc) is a gentler / better solvent for removing balsam and uv...
20. ## Thread: How Much Have We Accomplished?

by Nodda Duma
Replies
38
Views
2,063

### Re: How Much Have We Accomplished?

I successfully completed the ChromaGraphica Kickstarter campaign, getting everybody’s holders out to them and resolving the occasional issue.

Got the rest of the production shipped here and...
21. ## Thread: Kodak 2D Parts

by Nodda Duma
Replies
5
Views
370

### Re: Kodak 2D Parts

Kent, that looks like a Chicago bolt or Chicago screw. Measure ID of the hole and length you need, and look up a replacement part in McMaster Carr.

https://www.mcmaster.com/chicago-screws/
...
22. ## Thread: Aspherical, Apo(chromatic) & ED (extra low dispersion) lenses - whats the difference?

by Nodda Duma
Replies
26
Views
1,177

### Re: Aspherical, Apo(chromatic) & ED (extra low dispersion) lenses - whats the differe

It actually means correction at three wavelengths, so a bit more general than that. At least that’s what lens designers understand it as. I can’t speak for marketing misinterpretation.

Drew,...
23. ## Thread: Lens Separation Repair

by Nodda Duma
Replies
1
Views
280

### Re: Lens Separation Repair

I can help you with that, assuming the lens can be easily removed from the cell. Shoot me a message. Happy Thanksgiving!

-Jason
24. ## Thread: Aspherical, Apo(chromatic) & ED (extra low dispersion) lenses - whats the difference?

by Nodda Duma
Replies
26
Views
1,177

### Re: Aspherical, Apo(chromatic) & ED (extra low dispersion) lenses - whats the differe

Aspherical surfaces and ED glass are tools in the optical design toolbox, helping with certain aspects and having pros/cons but are not magical “solve-all” solutions.

Apochromatic refers to the...
25. ## Thread: Uneven Development -- 5X7's in Stearman Press 8X10 Tray

by Nodda Duma
Replies
24
Views
1,379

### Re: Uneven Development -- 5X7's in Stearman Press 8X10 Tray

I was talking to Tim once about this topic and I think he has determined that development issues in the tank have consistently come from too gentle of agitation.

Personally I pick the tank up and...
26. ## Thread: ChromaGraphica Double Dry Plate Holders now available for retail sale

by Nodda Duma
Replies
0
Views
195

### ChromaGraphica Double Dry Plate Holders now available for retail sale

ChromaGraphica Double Dry Plate holders now available for sale through the online shop under Accessories at www.pictoriographica.com

These are post-Kickstarter campaign holders, built here in...
27. ## Thread: Pictoriographica black glass!

by Nodda Duma
Replies
16
Views
748

### Re: Pictoriographica black glass!

No worries, Paul...didn’t take it as such. I was sharing in frustration that I can’t push the prices down much. My gial has always been to make plate shooting affordable. I could get the price...
28. ## Thread: Meniscus lens iris "sweet spot"???

by Nodda Duma
Replies
17
Views
1,213

### Re: Meniscus lens iris "sweet spot"???

You're talking about Coma, an off-axis aberration. The aberration illustrated in that link is coma as well.

Spherical aberration is an on-axis aberration, due to the lens not being the ideal...
29. ## Thread: Meniscus lens iris "sweet spot"???

by Nodda Duma
Replies
17
Views
1,213

### Re: Meniscus lens iris "sweet spot"???

Distance to the stop doesn't correct field curvature, only coma.

(Field curvature / astigmatism doesn't change with distance to stop.. what changes is where your flat image plane lands relative...
30. ## Thread: Pictoriographica black glass!

by Nodda Duma
Replies
16
Views
748

### Re: Pictoriographica black glass!

If it's not different, then offer it to folks who are looking for it. The wet plate community has been searching for this stuff for years.

I suspect, however, that it is different: the black...
31. ## Thread: Pictoriographica black glass!

by Nodda Duma
Replies
16
Views
748

### Re: Pictoriographica black glass!

Yeah I wish things were free, too. Unfortunately I can't sell it at a loss or I would. At least I don't have to make a living off this stuff.
32. ## Thread: Pictoriographica black glass!

by Nodda Duma
Replies
16
Views
748

### Re: Pictoriographica black glass!

Glad it showed up... looking forward to seeing what you and other people do with it.

Cheers,
Jason
33. ## Thread: Jamin Darlot Lens Restorer in UK or Europe or anywhere really!

by Nodda Duma
Replies
7
Views
561

### Re: Jamin Darlot Lens Restorer in UK or Europe or anywhere really!

I can re-cement the doublet for you, assuming I can get the glass out of the cell. Petzvals are a breeze. I’m in the US, tho.
34. ## Thread: 9x12 camera and all the things that come with it

by Nodda Duma
Replies
4
Views
315

### Re: 9x12 camera and all the things that come with it

Easiest way to go would be to cut down 4x5 sheets. I do this for whole plate color, taking some of my 8x10 sheets and cutting them down in the dark on a paper cutter (the classic guillotine type)...
35. ## Thread: Meniscus lens iris "sweet spot"???

by Nodda Duma
Replies
17
Views
1,213

### Re: Meniscus lens iris "sweet spot"???

The lens distance balances field curvature and astigmatism, with some effect on coma. Spherical aberration is corrected by the lens shape.

Coma, lateral color and distortion are corrected by...
36. ## Thread: Any tips on how to repair lenses with Balsam Separation?

by Nodda Duma
Replies
22
Views
1,122

### Re: Any tips on how to repair lenses with Balsam Separation?

It won’t be Canada balsam if made in that timeframe, and you won’t be able to separate with heat (and you’ll crack the lens if you do). Instead You’ll need to separate by soaking in methylene...
37. ## Thread: Chamonix Whole Plate Camera!

by Nodda Duma
Replies
35
Views
1,995

### Re: Chamonix Whole Plate Camera!

I’ve shot Whole Plate color... I cut it down with a paper cutter in the dark. Here is a Velvia 100 shot from a couple years ago.

208546
38. ## Thread: Chamonix Whole Plate Camera!

by Nodda Duma
Replies
35
Views
1,995

### Re: Chamonix Whole Plate Camera!

Yes. 6 1/2” x 8 1/2” is the standard size. I cut mine to just under that at 164 x 215 mm
39. ## Thread: Disastrous Consequences (solved: fog with Intrepid lensboard)

by Nodda Duma
Replies
51
Views
2,235

### Re: Disasterous Consequences

Someone posted the exact same problem either here or on photrio a few months ago. The cause were the Intrepid lens boards: Thry may look opaque but they are not! They do not block the full...
40. ## Thread: Dry Mountings vs Hinging and other aspects of presentation

by Nodda Duma
Replies
11
Views
606

### Re: Dry Mountings vs Hinging and other aspects of presentation

I started off hinging with corner holders, but several of the larger prints hanging on my walls have begun rippling from humidity after just 4-5 yrs. So I’ve gone to dry mount to keep them flat over...
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