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    Profile photo of ong_wsong_ws

    Dear all,

    got this ?? in mind for quite some time, have spent few days reading how others calculate the Magnification Rate … but still kind of confusing …
    Then came across an artical to get the magnification rate, do u guys think that its accurate or workable?
    The method goes like this:
    For macro lens, at the shortest distance we will get a 1:1 ratio ( base on a 35mm flim )
    So if i am to take a photo of a ruler with T180mm, from my viewfinders left to right i can get a reading of 0 to 50mm (at the lens min distance).
    Next i take another photo of the same ruler but with T180mm + XXmmET, now in my viewfinder i can get a reading
    of 0 to 37mm (at lens min distance).
    The difference in the reading is my mag rate ? Can i say that my mag rate is 1.35:1 (50/37=1.35) ??

    BTW how come i cannot attach photo ? normally beside the "option" tag we have "Upload Attachment"
    now i only have "option" :?



    Can’t help you on the technical aspect of this, but I fix the issue of not able to upload, please try again.


    Profile photo of ong_wsong_ws

    Hi SC,


    Profile photo of bluekitebluekite

    Hi WS,
    Ext tube is increase the FL. It’s the same I bring the ruler nearer to you. Becos you have the previour (wider) view, you think it is magnified. You can read the scale from 50 drop to 37 is already self-explained.

    Profile photo of NatureTTLNatureTTL

    Hi WS,

    Are you just quoting and example?. You should not get 50mm of the ruler at minimum focal distance of 1:1mag. if you are Canon or Nikon user. Unless your sensor is 50mm long, oh.. what camera system is that :? .

    Forget about the 35mm equivalent at this point, as it tends to confused things.

    At 1:1 lifesize magnification:
    You should get about 22.2mm of the ruler for Canon user or 23.6mm for Nikon user. (Sorry, can’t remember which system you’re using). For me (Oly user), at 1:1 mag, I get 17.3mm of the ruler.

    Your calculation is correct based on your example, the mag is 50/37 = 1.35.
    Or, for a rough estimation, if you’re adding on a 63mm ext.tube to T180mm, 63/180 = 0.35, where 0.35 is the additional magnification you’ll get on top of 1:1.


    Profile photo of LuennyLuenny

    Hmm … I never know that you can just divide the length of the ext tube with the focal length to get the extra mag. Thanks Allan. Now I know how to calculate it quickly.

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