Photoclubalpha

Pako, I believe you would be much better off using a remote flash in tele position ... The flash being in tele position won't make any difference beyond brightness. In wide-angle position, a greater portion of the flash gun's output would go astray and be wasted, that's all. Provided the flash has ...

agorabasta is right—the lighting will affect the character of your results ... in particular, visual sharpness, among other things. Basically, for slide copying you have the same choices as in an enlarger: diffuse or direct light. For diffuse light, use the white, non-transparent but translucent sc...

artington wrote:

01af wrote:In reversed mode, non-AF lenses are easier to use. [...]

Why are they easier to use reversed rather than mounted normally on say 50 mm tube combination?

Of course, they aren't.

Reversed non-AF lenses are easier to use than reversed AF lenses.

I want to reproduce slides with my digital DSLR (most probably the A850 and Minolta AF 50 mm 1:2.8; or the Minolta MD 50 mm 1:3.5; or a Nikkor EL 50 mm 1:2.8 ...) I already did a couple of tests, mostly at f/11 or f/16, and I'm not convinced by the results because the lack of sharpness—specially wi...

1:1 was what I meant. I see. So if the particular magnification of 1:1 is what you're interested in then you need the right amount of extension. For a 50 mm lens in normal mode, that will always be 50 mm. In reversed mode, it formally will be 50 mm, too, but the actual length of the extension tubes...

What you say essentially boils down to 'if something causes the blur at aperture tightening, it must be nothing but diffraction'. There must be something wrong with your reading comprehension. I didn't say 'nothing but'; I said 'primarily'. Great logic, congrats on that! Don't get me started on you...

If you're still willing to see diffraction and interference as the same thing then please note that ultimately, scattering also is nothing but a diffraction effect. Yet another piece of bunk ... Scattering may be of diffraction, refractive or reflective nature. The atmospheric scattering responsibl...

I'm a professional physicist experimentalist. That doesn't necessarily mean you were good at what you're doing. Another piece of typical bunk on your part. Well ... while talking of bunk—let's go back to this thread's beginning. There you say; "The fact is that the blurring at tight apertures ...

When you reverse this lens, do you get 1: to 1: macro or not? Huh!? What is "1: to 1: macro" supposed to mean? Anyway—when a lens is designed for subject distances that are longer than the lens-to-image distance then reversing it means optimising it for the use at subject distances that a...

If you check that plot at 250 mm f/40, it shows a very uneven non-uniform shape. Had the blur been caused by diffraction, that plot simply must have been pristinely smooth and uniform. This may mean only one thing—there's another mechanism creating that blur and it is considerably stronger than dif...

Now you're confusing interference and diffraction. It's exactly you who is supposed to know that diffraction is nothing more than interference :lol: Oh ... I think I am beginning to understand where your delusions are coming from. Obviously you're having the famous two-slit diffraction experiment b...

After all, if agorabasta actually was right then text books on physics and optics would have to be rewritten, and all those physicists, professors, and engineers of optics designing and building lenses, telescopes, and astronomer's observatories were just fools failing to understand what diffractio...

Modelling diffraction blur with a gaussian blur is a brain-dead idea. No, it's not. Of course I agree it's not a very accurate model—but good enough to see a point or two ... Diffraction creates secondary peaks AND troughs off the central spot. The problem is, you are wasting way too much thoughts ...

That's an interesting new design. Modern 50 mm standard lenses (for 35-mm format) with moderate lens speeds, i. e. 1:2, 1:1.8, or 1:1.7, typically are so-called Modified Double-Gauss systems with six elements in four or five groups (a "group" being defined as two or more cemented elements,...

Sorry I didn't read this forum for a while so I am late to this discussion ... but I don't buy the 'scattering' theory. That said, agorabasta isn't entirely wrong. It's true that diffraction is wavelength-dependent, so all other things being equal, red light will get diffracted more than blue light....