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Modding a bellows - what step size is optimal for stacking
  
 
JocoFoto
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p.1 #1 · p.1 #1 · Modding a bellows - what step size is optimal for stacking


All - I really hope someone can advise -

I have purchased a Novoflex Balpro 1 bellows. It is a wonderful bit of kit, but only the front standard is geared. The rear is friction only (although the setup can be used in reverse).

The plan is to mod the bellows so the rear standard is geared as well, using a setup similar to the RRS focusing rail. I.e.a threaded end along the length of the bellows and a turning nob at the rear.

The intention is to focus with the front standard and do the increments for focus stacking with the read standard using above mod.

Question is - what size of thread to use? I.e. how many mm's should the read standard move per rotation.

I am working mostly with a 100mm f4 (@f4 or f5.6 as indicated on barrel) at close up magnifications 1:4 or so. I do intend to venture into perhaps 2:1 at some point. I suspect the difference in step size between 1:4 and 2:1 is substantial - I try to find a balance between not having to turn XXX times at low magnifications and small increments of turns on a large knob at higher magnification.



Dec 26, 2016 at 12:14 PM
LordV
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p.1 #2 · p.1 #2 · Modding a bellows - what step size is optimal for stacking


There are some tables here which may be of use
http://zerenesystems.com/cms/stacker/docs/tables/macromicrodof

You probably need about a 30% DOF overlap of each shot

Brian v.



Dec 26, 2016 at 06:13 PM
R.H. Johnson
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p.1 #3 · p.1 #3 · Modding a bellows - what step size is optimal for stacking


doesn't the length of the bellows (distance from rear lens to sensor surface) establish the magnification factor? for critical focus the entire set-up (camera, bellows, lens) has to be moved to focus.

it would appear you would be better suited to add a second set of rails to achieve critical focus. take a look at the old Canon FD bellows. they incorporate dual gear tracks top and bottom. the top gear track retracts/extends the bellows for magnification. the bottom gear track moves the entire rail for focusing.







the old Nikkors and Minolta bellows are built with 2 gear tracks also.



Dec 27, 2016 at 02:05 AM
JocoFoto
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p.1 #4 · p.1 #4 · Modding a bellows - what step size is optimal for stacking


Thanks Brian - I'll do the math with those tables. How it'll pan out in real life i.e. how many (part-) turns are comfortable for my particular rig I'll have to just try, unless someone has experience with the exact same endeavour.

Nice setup R.H. - thanks for sharing! I have a rail to go with my bellows too. As you say, I use the front standard for magnification and then the rail for focus. But the stacking steps I do by moving the rear standard as that is the only way to keep the position of the lens (entrance pupil I think?) fixed relative to the subject. Thus preventing changes in perspective. Zerene Stacker can correct for the slight difference in magnification, but not perspective.

Some pictures:

stack 1 by Hans van den Bosch, on Flickr

stack by Hans van den Bosch, on Flickr

stack 2 by Hans van den Bosch, on Flickr

orchis by Hans van den Bosch, on Flickr



Dec 27, 2016 at 03:42 PM
 

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R.H. Johnson
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p.1 #5 · p.1 #5 · Modding a bellows - what step size is optimal for stacking


interesting, i was unaware of the intricacies of stacking. i shall experiment with stacking.


Dec 27, 2016 at 08:31 PM
scalesusa
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p.1 #6 · p.1 #6 · Modding a bellows - what step size is optimal for stacking


I wish I had watched this video before buying a bellows unit, it explains the pitfalls of using a focus rail. I found it to be one of a very few reviews of both expensive and low cost equipment.

https://lensvid.com/gear/choosing-the-best-focusing-rail-for-macro-photography/



Feb 12, 2017 at 06:54 AM
JocoFoto
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p.1 #7 · p.1 #7 · Modding a bellows - what step size is optimal for stacking


Good spot Scalesusa! I watched all Michael's videos (it took awhile......) and found a lot of inspiration in them and great advise.

One of the things I picked up was creating a panorama based on stacks. So I got an accessory to the BalPro1 bellows - the ProShift+. This enables you to shift the camera 1cm left and 1 cm to the right relative to bellows and lens. In practice what I do is take 3 series of images (right, middle, left position), stack each and finally stitch the 3 stacks to a panorama.

My sensor thus increases in size from 35x24 to 44x35, from 42MP to 80 or so. You obviously need a lens that has an image circle large enough to cover this area.

More work, more kit - but personally I can see the 'medium format look' it gives.

snowdrops by Hans van den Bosch, on Flickr



Feb 12, 2017 at 09:56 AM







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