1. Reminder: Please use our affiliate links for holiday shopping!

Macro magnification and crop factors question

Discussion in 'Adapted Lenses' started by rfortson, Mar 18, 2016.

  1. rfortson

    rfortson Mu-43 Veteran

    Okay, I understand all the other conversions/conversations/whatever about crop factors and such, but now I'm looking at some old macro lenses.

    I'm looking in particular at a 55mm macro that's listed as 1:1 magnification and a 100mm macro that's listed as 1:2 magnification. How does putting these lenses on my MFT cameras affect that magnification, at least in the image viewed. (Yes, I get that 100mm lens is a 100mm lens and we're just "cropping" a center portion for a FOV somewhat like a 200mm lens when we put it on our cameras.)

    The 55mm lens has a close minimum working distance and the 100mm is much farther away.

    Again, just looking to understand magnification from different macro lenses and what I can expect to see on a MFT camera.

    Thanks!
     
  2. fredlong

    fredlong Just this guy...

    Apr 18, 2011
    Massachusetts USA
    Fred
    The magnification ratio tells you how big an image will be projected on to the sensor at the closest focusing distance.

    1:1 means you'll have a life size image projected on the sensor. It is an actual measurement and never changes with format. Sometimes manufacturers, like Olympus for example, will give an "equivalent magnification" that is twice the size. This is meaningless. It is still a 1:1 projection on the sensor.

    The final magnification depends on both the lens and the amount of enlargement used in the final presentation of the image.

    Edited to add: Ask yourself how big is the thing I want photograph and how big is my sensor. That will tell you what you need for magnification.

    Fred
     
    • Like Like x 1
    • Informative Informative x 1
  3. piggsy

    piggsy Mu-43 All-Pro

    What are the lenses?

    The working distance will be influenced by a few things and it will be difficult to exactly compare the 55 to the 100 without knowing what the lenses are (some 100s get as short as ~70mm from focus breathing). The working distance of the 100mm will be longer just from only being 1:2 - the 55mm's at 1:2 would be longer as well.

    As fredlong said the concept of "magnification" is relative to the sensor in terms of capturing the image and output size in terms of display. There was an thread a while ago that goes into some of this -

    Macro question about DOF of ยต4/3 vs Full Frame
     
    • Like Like x 1
  4. rfortson

    rfortson Mu-43 Veteran

    Thanks guys, this is what I was looking for. They're both old K-mounts, one is a third party 55mm f/2.8 that's 1:1, and the other is an SMC-M 100mm f/4 that's 1:2. I used to shoot Pentax and so I have the adapter already.

    I want to shoot watches, so manual focus and max aperture don't really matter to me. I can throw light on the subject, but if I'm too close (like I fear with the 55mm) I'll have to watch shadows.

    I've been using the "macro" capability of the 12-50 which actually isn't bad, along with some cropping. I've also considered the 60mm macro and the 4/3 Zuiko 35mm macro, but I'd have to add $30 for an adapter for that. Also, that working distance is really close.

    Thanks for the help!
     
  5. piggsy

    piggsy Mu-43 All-Pro

    OK, the SMC-M 100 extends fully to focus and remains the exact printed length, so it's properly 100mm at all focus distances. How close up do you want to be? In terms of taking photos on m43, the closest focus on a 1:2 macro means the smallest (perfectly flat) subject that can be completely in focus will be 26mm high by 34.6mm wide. Do you want to take photos of objects significantly smaller than that like say disassembled watch guts or extreme closeups of other details?
     
    • Like Like x 1
  6. Carbonman

    Carbonman Mu-43 All-Pro

    Jul 10, 2014
    Vancouver BC
    Graham
    My watch is about 3.5cm across; a lens on a micro 43rds format camera only needs to get to about 1/2 life size magnification to fill the 17.3mm x 13mm frame from one side to the other. I don't know how much additional magnification you need. You get about 125mm working distance from the front element at that magnification.
     
    • Like Like x 1
  7. fredlong

    fredlong Just this guy...

    Apr 18, 2011
    Massachusetts USA
    Fred
    The 100mm at 1:2 should be enough. If you need to get closer occasionally you could add an extension tube.

    Fred
     
    • Like Like x 1