[FrancisK7]

I'm planning on acquiring the DA*300 so I can shoot with my DA35 Macro reversed on the other end for 8x magnification. I will also get a Stackshot rail to make focus stacking easier.

However, I am trying to determine what my working distance from the subject would be and can't figure it out. The physics of it I mean.

Would I still be working at 45mm like I am right now with a Raynox 250?

[VisualDarkness]

Have you thought about the control over the aperture on the reversed DA35? It will always be fully stopped down if nothing push the lever.

[audiobomber]

A reversed lens will focus at its registration distance, for a K-mount lens that would be 45 mm. As VisualDarkness said, you have a problem because the DA 35 macro has no mechanical aperture control. How are you going to hold the aperture open?

[Na Horuk]

The dude is about to buy a DA 300mm, I think he can afford a piece of duct tape to hold the aperture lever
Not that I'm actually advising that, you don't want any sticky residue

[baro-nite]

You'll also have major vignetting. There are many reasons to buy the DA*300, an outstanding lens, but 8:1 macro probably shouldn't be one of them. I've been playing around with reversed lenses on extension and trying to understand more about the effects of extreme magnification -- I've found this site very helpful:

Optics articles

Getting usable shots at extreme magnifications, which I'll define as anything significantly beyond 1:1, comes with many challenges. You might want to look into microscope objectives:

Microscope objectives in photography | Flickr - Photo Sharing!

[FrancisK7]

I didn't think about the lack of aperture ring, err. I'm certainly not sticking doc tape on it!

I've had good success with focus stacking in Zerene with a 100mm Macro lens and a Raynox 250. With a stackshot macro rail to automate the exposures at 0.1mm increment I could probably get nice results even at 8x.

I'll look into microscope objectives but was led to believe the quality will not match two quality lenses reversed together.

[audiobomber]

I would try a manual 28mm on the end of the DA*300. Old 28mm's are easy to find, inexpensive and most have good IQ.

OTOH, that's an expensive solution. An inexpensive solution would be bellows or tubes and a reversed 28mm.

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Last edited by audiobomber; 02-06-2013 at 11:06 AM.

[baro-nite]

I'll look into microscope objectives but was led to believe the quality will not match two quality lenses reversed together.

Look at the second link I posted -- it starts off with a shot at 45:1.

The problem with 8:1 macro is diffraction. Well, on top of all the other problems -- stability of camera and subject, moving either or both into position, focusing, lighting. Some of these microscope objectives have a large effective aperture.

If you can get good results at 8:1 with the 100mm macro and a Raynox, that sounds like the way to go.

[FrancisK7]

It's not 8:1 with the Raynox, it's 3.5:1 and not enough magnification for my current project.

I'm impressed by the Reichert 6.5 for sure but can't seem to find it anywhere.

Thanks for the reading suggestions, I'm on it!

[audiobomber]

You'll also have major vignetting. ]

I'm not sure that's correct.

[baro-nite]

I'm not sure that's correct.

That ought to teach me not to make assumptions. You're right and I was wrong; just did a test holding a vaguely similar lens up against the DA*300 and got no vignetting. Certain lens stacks do vignette, but not this one. I still think 8:1 is asking too much of such a combination, because of diffraction, but if I'm wrong about this it wouldn't be the first time.

[audiobomber]

I still think 8:1 is asking too much of such a combination, because of diffraction,

I don't see why a stack would be more subject to diffraction than a single lens. F11 is usually taken as the onset of diffraction, but it's commonly accepted practice to use even smaller apertures for macro. The OP is using a good stand in a studio and focus stacking, so the usual macro challenges are being controlled.

[FrancisK7]

So all I really need for this to work (aside the from the rail and the stacking method) is a lens with an aperture ring? Any other criteria?

[baro-nite]

I don't see why a stack would be more subject to diffraction than a single lens.

It isn't (as far as I can understand). But magnification changes the effective aperture of any optic. For a symmetrical lens (entrance and exit pupils the same size) the effective aperture is (M+1) times the nominal (on the lens) aperture. f/4 on the lens becomes effective f/36 at 8:1 magnification.

So all I really need for this to work (aside the from the rail and the stacking method) is a lens with an aperture ring? Any other criteria?

Sounds good to me -- as long as the secondary lens (the reversed one) has an aperture ring, and the particular combination of lenses doesn't vignette, you're ready to shoot. You might want to rig up a hood to protect the rear element of the secondary lens as it will be rather exposed otherwise -- a lens cap with a large hole drilled in it is not bad.

I'll be interested to see what you come up with. As I said I'm just getting into this area myself; for now I'm looking more at using a single lens reversed on extension.

[audiobomber]

It isn't (as far as I can understand). But magnification changes the effective aperture of any optic. For a symmetrical lens (entrance and exit pupils the same size) the effective aperture is (M+1) times the nominal (on the lens) aperture. f/4 on the lens becomes effective f/36 at 8:1 magnification.

My turn to get it wrong. I found this tutorial that explains what you said. Macro Camera Lenses