Fotozine “Žičani okidač” : ISSN 1334-0352 : s vama od 6. 6. 1998

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odlično štivo za makroljupce
pogled_u_bb
[18. 11. 2008.]

Našao sam jedan odličan tekst koji objašnjava prednosti i mane pojedinih tehnika macro snimanja (predleće, makroprstenovi) pa sam ga copy/paste

1) Achromats that are much less powerful than the lens you use them on do not affect image quality much, but they also don't magnify much. The 500D diopter is nothing more than a nice 500mm lens. Put it on an 85mm lens, and it's focal length is 6x that of the 85mm lens. The 85mm's "personality" dominates, as far as distortion, chromatic aberration, spherical aberration, etc...

Put that same 500D on a 35mm lens, and there's almost no magnification, and very little effect on image quality.

2) Achromats that are closer to power of the lens that you use them on give you a lot of magnification, and a sever effect on the image quality. On a 70-300mm zoomed to 300mm, the 500mm 500D is nearly the same strength as the 300mm main lens, so they wrestle for domination, magnification soars to nearly 1:1 (cool) and you get the worst distortion (not so cool). The distortion and aberrations are more like those of the simple 2 element diopter than they are the 18 element telephoto. In general, this is a "bad thing". It takes a lot of elements to give you good quality images, that's why telephotos and zooms have anywhere from 7 to 25 elements. When you let a 2 element lens dominate, you get, well, the image quality of a 2 element lens.

3) Extension tubes are the enemy of wide angle and normal zooms. You can put an extension tube on a normal prime like a 50mm f1.8, or a wide angle prime like a 20mm f2.8. The working distance (distance from the front of the lens to the subject) will decrease. On the 20mm, with a 12mm tube, working distance is about 12mm (1/2 an inch). It's scary putting the front of an expensive lens that close to the subject. But if you put a 12-24mm lens on a 12mm tube, the plane of focus actually moves inside the lens. Since your subject can't do that (it is very hard on the lens to try) you can't actually get an image. Even lenses like a 24-70mm don't work well on tubes unless you zoom them all the way out to 70mm.

4) Extension tubes work best with longer lenses. Those have the most latitude in focusing extension, a little more usually doesn't add much distortion.

5) Achromat diopters are easier to use on zooms than extension tubes are. With a diopter on a zoom, once you manage to achieve focus, you can change magnification by zooming the lens. With a tube, zooming results in dramatic shifts in focus.

6) It sounds counter-intuitive, but coupling two lenses together often yields superior results to either tubes or diopters. Lenses (except for expensive macro lenses) are built to do one thing well: take an image plane far away from the front of the lens (typically 2m to infinity) and project it on a plane (the sensor) about 39mm behind the back of the lens. When you use extension tubes or diopters to "bully" a lens into doing something other than that, it gets all sulky and miserable and doesn't perform well. But light goes through a lens both ways, front to back, and back to front.

So, when you put two lenses together, face to face, you're actually letting them both do what they do best: one takes the subject 39mm from the back of the backwards lens, and projects it at infinity. The other "picks up" the projection at infinity, and projects it onto a sensor 39mm from the back of the lens. So, you mat think that an 18 element 70-300mm zoom on the camera with a 7 element 50mm f1.8 is too many elements (25, all total) but each lens is doing something that it was built to do, and together, they do pretty good macro...


kisd
[18. 11. 2008.]

Slazem se, ali ipak koristim achromat na Sigmi 90 macro, bez vecih problema. Objekti u centru slike su ostri, a kod macro snimki ionako kadar nikad nije ispunjen u potpunosti.

Joe

gogoya
[18. 11. 2008.]

a bo, ja koristim makro prsten sa 135mm staklom, pa ne vidim nikakvih problema ...

seewolf
[18. 11. 2008.]

http://fotozine.org/?knjiga=forum&poglavlje=403&list=5297

netko spominjao macro? :).. ja sam oduvjek za macro prstenove i na njima nes tipa 50mm ili 85mm (u zadnje vrjeme i 70-200) i to je meni jednostavno najbolje i najjednostavnije :)..

napominjem ovo je posve subjektivan stav :).. predlece su mi preskupe i neda mi ih se sarafiti.. bas nemogu na svaki objektiv (bar ne bez adaptera za promjer).. obrnuti objektivi su mi tlaka i nisu moj stil.. macro objektivi ah.. sta ce mi macro objektiv kada imam macro prstenove i dva bolesna primea :)..

spetreko
[19. 11. 2008.]

...ja imam za prodati 500D (77mm), izvrsna leća 70-200mm!

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