Lomo 3,7 x .11 beginner set up question

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altereddecay
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Lomo 3,7 x .11 beginner set up question

Post by altereddecay »

Greetings,
Im new here and have been shooting some simple stacks with my Nikon D800 and 105mm lens using Helicon Focus. I love it and wanted to expand and recently purchased at Lomo 3,7 x 11 Objective and have a WeMacro but I have questions. Based off of my readings from the forums I do not think I need a tube lens but rather 160mm of extension? I currently have the following pieces to attach the Lomo directly to my D800... Not sure if this would work...
F-mount to 52mm
52mm Female-Female adapter
52mm to RMF
Lomo 3,7 x 11 Objective

If I need the 160mm extension I'm looking at ThorLabs:
SM2 Lens Tube, 3" Thread Depth
SM2 Lens Tube, 2" Thread Depth
Ø2" Adjustable Lens Tube, 1.31" Travel
Slip Ring for SM2 Lens Tubes

This would get me to the 160mm extension based off of the info at
https://www.closeuphotography.com/lomo-3-7x-objective
and https://www.closeuphotography.com/52mm-setup

Is this correct ?

Pau
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Post by Pau »

The 160mm tube length specification refers to the distance between the objective shoulder and the end of the microscope tube; in most cases the primary image is formed 10mm bellow it, so the right optical distance from the objective shoulder to the sensor would be 150mm.*
That said these low magnification objectives are very tolerant to changes in TL, you can play with it quite a bit and you will have changes in magnification (and focus point)

Despite corrected for a finite tube length some people (mainly Robert O'Toole) have experimentally found that the use of an intermediate converging lens ("tube lens" by similarity of microscope naming) can improve it, take a look at:
https://www.closeuphotography.com/lomo-3-7x-and-sr120

* Robert says 155mm, maybe LOMO is a bit different although this doesn't matter much here
Pau

altereddecay
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Location: OAKLAND CA
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Post by altereddecay »

Pau, Thank you for the response. Measuring my Nikon 105mm it is exactly 150mm from season to the RMF adapter so I think I'll give it a try and see what I get before ordering the extension tubes.

viktor j nilsson
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Location: Lund, Sweden

Post by viktor j nilsson »

altereddecay wrote:Pau, Thank you for the response. Measuring my Nikon 105mm it is exactly 150mm from season to the RMF adapter so I think I'll give it a try and see what I get before ordering the extension tubes.
It seems like you are mixing up some things. The physical length of your Nikon lens is not important, only it's optical focal length.

EITHER you place your Lomo 3.7x on an empty extension tube so that it is located 150mm from the sensor. This is the finite configuration. You can alter magnification by changing the length of the extension a bit.

OR you place your Lomo in front of an lens like your Nikon 105mm,
This is the infinite configuration (the Nikon is your tube lens). The tube lens should focus at infinity. In this case, the magnification is given by: focal length of tube / focal length objective.

The Lomo has a focal length of 32.8mm according to Robert's site. That's why he got 3.7x magnification with his 120mm lens (120/32.8=3.66).

With your 105mm lens, you would get 105/32.8=3.2x magnification. Worth trying!

altereddecay
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Joined: Fri May 22, 2020 8:15 am
Location: OAKLAND CA
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Re: Lomo 3,7 x .11 beginner set up question

Post by altereddecay »

Thank you, this helps! I was indeed gettin confused with the focal length vs physical distance in mm. At 3.2x its giving me a 50um step where I had been using a 42mu step thinking I was using a 3.7x. Now Im playing with the other settings to try to get a better understanding and better results. Unfortunately Helicon Remote and Focus are very buggy with my Mac OS and require force quits after every render.

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