Crop Body math

Discussion in 'Photography Beginners' Forum' started by Misfitlimp, Aug 21, 2009.

  1. Misfitlimp

    Misfitlimp TPF Noob!

    Joined:
    Jul 8, 2009
    Messages:
    375
    Likes Received:
    1
    Location:
    Fillmore, CA
    Can others edit my Photos:
    Photos OK to edit
    So i own a canon 50D and I know the lens i use isnt what it seems. For example if i have my lense at say 28mm it really isnt 28 because i have to multiply it by 1.6 so my question is do i add the diffrence or do I just multiply for example 28x1.6= my actaul focal length or is it 28x1.6=x and then i add x to my 28mm to get my actual focal length? sorry for the newb question and for turning TPF into math class.
     
  2. FrankLamont

    FrankLamont TPF Noob!

    Joined:
    Feb 20, 2009
    Messages:
    556
    Likes Received:
    0
    Can others edit my Photos:
    Photos NOT OK to edit
    Your 28mm lens would have an equivalent of 44~45mm in 35mm film format/full frame.

    In other words, don't worry about it, unless you're judging ultra wide, in which case get a 10-22mm for the equivalent 16-35mm.
     
  3. Misfitlimp

    Misfitlimp TPF Noob!

    Joined:
    Jul 8, 2009
    Messages:
    375
    Likes Received:
    1
    Location:
    Fillmore, CA
    Can others edit my Photos:
    Photos OK to edit
    My question was how did u come to the conclusion that its 44-45? Im worring because im taking a class and on an assignment my instructor gave us he asks for certain things like to set our lense at 50mm if i go and set it to 50mm and it actually isnt 50mm I would not b fullfiling reqiuerments i have for that said assignment so you can see my predicament.
     
  4. camz

    camz No longer a newbie, moving up!

    Joined:
    Jun 11, 2009
    Messages:
    1,878
    Likes Received:
    284
    Location:
    Bay Area
    Can others edit my Photos:
    Photos NOT OK to edit
    So the forumla would be 1.6 x (lens focal length) = actual focal length

    That's how he/she got it 28mm = 44~45mm
     
  5. Montana

    Montana TPF Noob!

    Joined:
    May 27, 2008
    Messages:
    1,533
    Likes Received:
    0
    Location:
    Eastern Montana
    Can others edit my Photos:
    Photos NOT OK to edit
    Multiply the focal length of the lens by 1.6. 50mm lens=80mm field of view. Its still a 50mm lens though. I think you should talk to your instructor a little. Is he wanting you to take pictures using 35mm equivalents?
     
  6. Misfitlimp

    Misfitlimp TPF Noob!

    Joined:
    Jul 8, 2009
    Messages:
    375
    Likes Received:
    1
    Location:
    Fillmore, CA
    Can others edit my Photos:
    Photos OK to edit
    Well he knows people have crop bodys and he told everyone the whole 1.6x deal and wants us to figure it out. so im sure he wants full frame equivalants. so if i wanted 50mm i would shoot at about 35mm?
     
  7. Montana

    Montana TPF Noob!

    Joined:
    May 27, 2008
    Messages:
    1,533
    Likes Received:
    0
    Location:
    Eastern Montana
    Can others edit my Photos:
    Photos NOT OK to edit
    yes.

    Is the class have people with both film and DSLR cameras? If it is all DSLR, I would think that the majority of the class would be shooting crop. (full frame DSLR being a tad on the expensive side for college kids) Good to see you taking a class. I wish there were some offered near me.
     
  8. Misfitlimp

    Misfitlimp TPF Noob!

    Joined:
    Jul 8, 2009
    Messages:
    375
    Likes Received:
    1
    Location:
    Fillmore, CA
    Can others edit my Photos:
    Photos OK to edit
    Thanks for the help guys
     
  9. KmH

    KmH Helping photographers learn to fish Supporting Member

    Joined:
    Apr 9, 2009
    Messages:
    38,237
    Likes Received:
    5,008
    Location:
    Iowa
    Can others edit my Photos:
    Photos OK to edit
    Just to be clear.

    The focal length of your lens is 35mm regardless, and the crop factor produces an image that would have the same Field-Of-View (FOV) that a 50 mm lens would have on a full frame (35mm) camera.
     
  10. CW Jones

    CW Jones TPF Noob!

    Joined:
    Feb 26, 2009
    Messages:
    813
    Likes Received:
    0
    Location:
    Connecticut
    Can others edit my Photos:
    Photos OK to edit

    Ok well to start off with... the teacher will never know that it wasn't set at 50mm.... most teachers say to use the 50mm because it close to what the human eye sees.

    Edit: second thought... I guess the teacher will know if its a digital class, I assumed it was 35mm for whatever reason haha
     
  11. choudhrysaab

    choudhrysaab TPF Noob!

    Joined:
    Jul 11, 2009
    Messages:
    667
    Likes Received:
    0
    Location:
    Toronto, Ontario. Canada
    Can others edit my Photos:
    Photos NOT OK to edit
    you're welcome :)
     
  12. tom beard

    tom beard TPF Noob!

    Joined:
    Mar 2, 2009
    Messages:
    175
    Likes Received:
    5
    Location:
    So. Cal mountains east of LA
    Can others edit my Photos:
    Photos OK to edit
    I am a noob too and was confused. I found out that the FX format sensor is the same size as a standard 35mm frame, so an 18-105mm=18-105. The DX format sensor is smaller so the Field of View (FOV) changes. In the DX format an 18-105mm translates to 27-157.5mm. That is called the APS Equivalent (Advanced Photo System). I found a website that does the math for you. It is: slrgear.com/reviews/showcat.php/cat/13. They have a long list of lenses (focal lengths and brands). Just find the lens you want, click on it on it and then click on Specifications. Five lines down the APS Equivalent is listed. It will also list many other specs. I found this very helpful.

    Tom Beard
     

Share This Page

Search tags for this page

franklomont graphy