Originally posted by newarts Eureka!
A partial solution is to reverse mount a camera lens with a long flange registry distance!
Medium format lenses meet this criteria. Here's a short list from
Lens Adapters - Photoethnography.com's Classic Camera DB
Lens type.........Registration, mm
Hasselblad .........74.90
Kiev 88 .............82.10
Pentax 6x7 .......84.95
Mamiya RZ ......105.00
Mamiya RB ......112.00
See
Camera Mounts Sorted by Register for more.
For example, buy a $100USD Kiev 88 (Pentacon six) wide angle lens and reverse it on a bellows! It will meet your working distance and mag specs. Here's a 45mm example:
Lens "Mir-26V" 3.5/45mm for KIev-88 TTL - eBay (item 160519719715 end time Mar-15-11 03:47:02 PDT)
The appropriate estimation equations for reversed camera lenses are:
Reversed.lens.working.distance = f/m + registration distance
Reversed.lens.extension.on.Pentax.K = f(1+m) - 45.5
working distance.Kiev88.45mm = 45/5 + 82 = 91mm
bellows.extension.Kiev88.45mm = 45(1+5) - 45.5 = 224.5mm
You won't find many shorter focal length medium format lenses that aren't fish-eye, so a compromise would be an Adaptall, T-mount, or Leitz Visoflex I lens:
Lens type................Registration, mm
Tamron T Mount ..........55.00
Tamron T2 Adaptall ......55.00
Leitz Visoflex I ..............65.50
For a $30USD reversed 28mm Tamron
Tamron Adaptall 2 28mm f/2.5 Wide Angle Fast Lens Canon - eBay (item 230594399533 end time Mar-13-11 18:39:47 PDT)
working distance.Tamron.28 = 28/5 + 55 = 60.6mm
bellows.extension.Tamron.28 = 28(1+5) - 45.5 = 122.5mm
I think the Tamron Adaptall 28mm approach might come close to simply meeting your needs; a simple bellows would meet your 5x specification and it misses the working distance by only 10mm at 5X and only 3mm at 4X.
Another approach is to reverse mount a wide angle medium format lens onto a long primary lens to take advantage of the MF lens' long registration distance. My tests show that doing so changes the effective registration distance for the MF lens. My 65mm Kiev 88 (Pentacon Six) reverse mounted on a 300mm primary lens has a working distance around 62mm. Not too bad, but it demonstrates how stacking changed the MF lens' effective registration distance (in this case it decreased by at least 20mm)
Some time passed and things settled a bit...
Dave, your information is of great value! That is some comprehensive research.
yeatzee and RXrenesis8:
Yes, I might have exaggerated on the optical degredation with stacked lenses. But in the set-up I used chromatic aberations were rather nasty.
I blame the SMC Pentax - may look way better with another lens.
Normally when I lust for something I have the excitement whenever I see the object of lust - however this didn't really happen here.
So I came to the conclusion that this was more of a *really want* thing not a *need* (ok, need is very subjective. Nobody needs a camera).
Being pragmatic I'll try to keep the potential wast of money down by going the cheaper route first.
Bellows and MF/enlarger lenses are still on my mind but for now I'll go with a set of step-down rings (82-77 for the circumstance I get a Sigma 24-70 one day) to put my 77mm threaded lenses on the macro adapter
pro Step down ring set 82-77-72-67-62-58-55-52-49 8pcs bei eBay.de: Lens Accessories (endet 19.04.11 00:52:11 MESZ),
a 77-77 male coupling adapter (thanks RXrenesis8) so I can try my 28 and maybe 16-50 on the 105 and 70-200
77mm 77-77 male to male Macro reverse coupling ring bei eBay.de: Filter Accessories (endet 17.04.11 12:49:14 MESZ),
a simple 2-way focusing rail which should also eliminate the need to get a 2 geared bellows
2 Way Macro Focusing Rail Slider K4G Canon Nikon Pentax bei eBay.de: Tripods (endet 24.04.11 10:00:23 MESZ),
the tele lens hood I was writing about in the other thread which also functions as a fixed extension tube (getting 2 for 148mm extension) for reversed lenses
Quality 77mm 77 Tele Telephoto Lens Hood Shade Metal bei eBay.de: Lens Hoods (endet 18.04.11 01:46:41 MESZ)
and to be prepared for the bellows option a cheap M42-PK adapter that allows for infinity focus
M42 to Pentax k10d k100d K110D K20D DL adapter infinity bei eBay.de: Lens Accessories (endet 02.04.11 14:07:55 MESZ)
Total cost about $75.
That should keep me busy for some time and reveal if I still feel the urge to go deeper with doing super macros.
Your assistance and advice is highly apprechiated.
Last edited by Egg Salad; 03-27-2011 at 07:24 AM.