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Thread: lens err... name ...

  1. #1

    Red face lens err... name ...

    hi everyone i just have a simple qn
    it's about lenses. they all have names i wanna understand.
    like : Canon EF 50mm f1.8 or Pentax 50mm f1.4 MF

    i understand that 50mm is the focal distance and f1.8 is the apature value
    but 50 focal length is how long? 50mm?(i just find no sense as so many lens are like 50mm or 35mm or somewhat similar naming so everyone of them can only take objects close or wat?)
    what is the exact meaning of their names?

  2. #2
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    Figure like 50mm is actually the lens focus lenght. It also some kind of figure we show what kind of lens was used to shoot the picture. 50mm on 135 film format is the standard lens, why because the viewing angles is very close to our eye. Therefore lens shorter then 50mm in focus length like 35mm or 20mm are wide angle, they see more viewing angles or wider angle then our eye or the 50mm. So lens longer than 50mm like 85mm or 300mm are telephoto they see less viewing angle but subject seem closer.

    Yet again this affected by the film format you use will result in different focus lenght for standard or wide angle or tele. For example 50mm is the standard for 135 or small format, on a 120 6x6 or medium format 6x6 the standard is 80mm and a 4x5 large format the standard lens is 135mm. Then there the zoom lens it is just a lens that have different focus length in one lens. For example 28mm-200mm zoom lens in a 135 camera. This mean it allow you to use different focus lenghts from a wide angle 28mm up to a telephoto one of 200mm in one lens.

  3. #3

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    ok i think i kinda get the 50mm thingy. 50mm focus length is like what our eyes see and anything less than that is a wide vision (horizontally right?) and more than that is telephoto.
    But, 1) i don't understand what is 135 standard and why is it a small format? or 120 film format. And does that 6x6 mean 6inches x 6inches? 135 camera ? So film actually have multiple standards? how about digital?

    2) So back to my question, how can i know from the name like "Canon EF 50mm f1.8" what focal length range is it for?

  4. #4
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    Btw, do you have a digicam ? I believe most digicams are based on the 35mm format. So you can use your digicam and zoom in to 50mm focus length and that should be what you can see with the Canon EF 50mm f1.8 on a full frame DSLR or film camera.
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  5. #5

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    all digicams are based on the 35 mm format... 35mm = 135 format...
    tink like this, 35mm is the size of the film u normally use...

    120 format is a 6x6 inch format....which is wat we call MEDIUM FORMAT...bigger film = bigger blowups... w/o loss of resolution...

    canon EF 50mm 1.8 means the focal length is 50mm.... the type of camera it is made for will depend on its mount...they have 50mm for MF cameras too.... juz as they have it for SLR... these are not names...they are specifications...

  6. #6

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    i'm using a canon A75. But with zooming how do i know if i've reached 50mm focal length?

    so u say most digicams are based on 35mm format. So how do i know which format i'm using?

  7. #7

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    MF cameras?

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    think he's refering to Manual Focus Cams.....ie...not auto fucus...

  9. #9

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    ya digital camera is definately a 35mm format .... MF(6x6) is square one ...
    digicam sensors are made based on the 35mm film size....and because its smaller than the normal film plane by abit...therefore the 1.5x cropping factor tt is so much heard of....

    how u know how much is 50mm....?? for ya digicam after u take the photo should be able to see the data...

    got time come my house la....i show u everything... SLR DSLR medium format....wateva...

  10. #10

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    wah lao... u stay in... i can only go on weekend.
    or u can be my bitch then i everyday go ur house liao ... haha...

    hmm.... just say can? *sly smile* so after taking the photo, i'll be able to see from the properties menu isit?

  11. #11

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    be ya b*^9(....u got one enuff liao la hahah...

    how would i know?? i dun own the same cam as yours.....

  12. #12

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    SLR cameras let you attach different lenses so you can see the scene at various magnifications. The magnification power of a lens is described by its focal length (mm).

    In cameras, the focal length is defined as the distance between the lens and the real image of an object in the far distance. Understand this as the distance between the flim plane / CCD and the optical center of the lens

    (NOT THE SAME AS THE PHYSCAL CENTER OF LENS) it really depends on how the lens gets made... hence diffent sizes, the sigma 50-500 can be smaller than a 300mm for example.

    Just note higher focal length number indicates a greater image magnification.



    EF 50mm 1.8 Mark II

    OKay,

    EF - Electrofocus a name canon devised to brand their new line of lenses that suceeded the older range, compatable with EOS cameras. Nikon uses like AF or AF-S or AF-D, all having their own meanings like -S being silent wave motor, and D being the distance chip for 3D metering applications

    50mm - as discussed it is the focal length, this affects how a picture looks and how far away u have to stand from an object of a certian fixed size to fill the frame (magnifcation). This also affects persepective, u know, when u look at a picture and it looks like woah!! heck alot of space... and the things in the foreground are like HUGE! thats probally taken with a wide angle lens 24mm perhaps. but if it looks like what ur eyes is used to seeing, it cld be a 50mm lens.

    1.8 - Maxium Aperture value. This denotes the maxium amount of light that can pass throught the lens. glass is not all that clear, u lose light when u stack glass infront of it. Smaller numbers make faster lenses. This also affects whats called depth of Feild (DOF) at 1.8, the area in focus is shallow compared to say F8. Remeber the expriments in school? smaller pin hole sharper image? same goes. the aperture is a mechnical iris that closes in to form a smaller opening to get you a shaper image.

    Mark II - denotes its a second edition of the lens. thats all. u may find other words here like USM, meaning ultra sonic motor a kind of motor used by canon in some lenses, in Sigma they are called HSMs. You may find the word Macro there, with denotes that the lens is made to focus closer than that of those with the same focal lenght, giving u high magnification at the same focal lenght.



    Here a link thats good in describing focal lenght and crop factors:
    http://digilander.libero.it/fotorepo...ca/sk_05_e.htm

    basically crop factor happens due to a physically smaller size of the sensor, like when we were kids and held cardboard tubes to our eyes, its not that we saw further, its jsut a cropped view.
    Last edited by moos blues; 17th November 2004 at 11:12 PM.

  13. #13
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    Quote Originally Posted by Witness
    120 format is a 6x6 inch format....which is wat we call MEDIUM FORMAT...bigger film = bigger blowups... w/o loss of resolution...
    mistake here.

    135 format == 36x24mm format (aka 35mm)
    120 format == 4.5, 6, or 9 cm by 6 cm (note, cm, not mm) also called medium format
    large format = 4 inch x 5 inch, 8 inch x 10 inch etc

  14. #14

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    Quote Originally Posted by Witness
    ya digital camera is definately a 35mm format .... MF(6x6) is square one ...
    digicam sensors are made based on the 35mm film size....and because its smaller than the normal film plane by abit...therefore the 1.5x cropping factor tt is so much heard of....

    how u know how much is 50mm....?? for ya digicam after u take the photo should be able to see the data...

    got time come my house la....i show u everything... SLR DSLR medium format....wateva...
    Actually, wrong, most digital cameras are technically APS-C format, other then full frame DSLR.

  15. #15

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    Quote Originally Posted by sehsuan
    mistake here.

    135 format == 36x24mm format (aka 35mm)
    120 format == 4.5, 6, or 9 cm by 6 cm (note, cm, not mm) also called medium format
    large format = 4 inch x 5 inch, 8 inch x 10 inch etc
    So actually 135 format or 120 format is it the physical size? or is it a format?
    cooz i tot my A75 can take like digital size which is like 5x6in? am i right?

  16. #16

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    APS-C? what do you mean?

  17. #17
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    Quote Originally Posted by nipapa
    So actually 135 format or 120 format is it the physical size? or is it a format?
    cooz i tot my A75 can take like digital size which is like 5x6in? am i right?
    A75 or whatever, in digital terms, there is NO such thing as a 5 x 6 inch. the size of your print, is determined when you ask the shop (or command your new printer ) to print out at a certain size, then the photo will be scale accordingly, and the dot density (dpi) will be dependent on the number of pixels in the photo you're printing; as well as how large you want to print. my 10D's 3072x2048 photos can hit 512 dpi (logically speaking) if i want to print in 4R (6x4 inch) because 3072/6 and 2048/4 gives 512.

  18. #18
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    Wow lively dicussion here. 135 or 35, 120 and 4x5 large format are film format to lable the different film sizes. They are not to be confuse with the digital one.

    For DSLR when they said full frame sensor or CCD they are saying their sensor is of 135 or 35 film frame size. Then if they have 1.5x factor from sensor actually the sensor is smaller then a 135 frame size, so you need to multipy your focus length by 1.5. For example a 50mm on a 20D camera which a factor of 1.6x is equal to 80mm on reference a 135 film camera. Like the film format. The type of lens changes on the digital, but base on reference to the 135 frame size.

    So in order to know what lens the person used to shoot the picture you need to know what the focus length and the type of format the person using. So you will get head and tail, it is a wide or tele lens. For example if I say I use 90mm to shoot this picture and stop here. Do you know what lens it is? 90mm on a 135 small format camera it is a short telephoto lens, on a 120 6x7 (6cm by 7cm) medium format camera it is a standard lens and finally on 4x5 (4in by 5in) large format camera it is a wide angle. Then to confuse you farther what if it a Canon 20D digital camera? It still a 90mm but a telephoto lens with a effective focus lenght of 144mm again in reference to a 135 film format camera.


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    Oh I miss out APS. APS or advance photo system is a film format smaller than 135 or the small format. So it is a smaller format, becuse then there 110 or the minature format. Any one know what a 126 or 128 or 220 hehehehe just too many out there.

  20. #20

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    Quote Originally Posted by singscott
    Then to confuse you farther what if it a Canon 20D digital camera? It still a 90mm but a telephoto lens with a effective focus lenght of 144mm again in reference to a 135 film format camera.

    wow! you really did confuse me there... a 90mm on a 20D camera should be a tele right? maybe like 1.7x smthing isit?


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