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Aperture values of 43 lens on m43 body?

Discussion in 'Adapted Lenses' started by rdo, Aug 30, 2012.

  1. rdo

    rdo Mu-43 Rookie

    15
    Aug 26, 2012
    Hi all,

    I'm bit confused about the focal length and the effective aperture values when using four thirds lens on m43 body. Does the focal length change like for the the film lenses? Does the aperture value change also?

    In the user manual of my epl1 there is written that for OM lenses the effective aperture also doubles (and the focal length). Is there such change for the four thirds lens?

    I'm planning to get the 14-54 f2.8, because they are faster than my current kit lens, but if the values change when used on m43 - then there is no point of doing this.

    Cheers
     
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  2. Vivalo

    Vivalo Olympus Loser

    941
    Nov 16, 2010
    Finland
    As long as you use the MMF adapter with it, it will be just as m4/3 lenses. Only a little slow to focus. Aperture values and focal lengths are always the same what ever system you use. So the field of view and aperture value is the same on OM 50mm lens and 50mm m4/3 when they are used with m4/3 sensor.
     
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  3. Vivalo

    Vivalo Olympus Loser

    941
    Nov 16, 2010
    Finland
    And note that m4/3 and 4/3 sensors are the same only the flange back (distance between lens mount and sensor) is different but that doesnt matter because the adapter is to get the 4/3 lens far enough from the m4/3 sensor.
     
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  4. Cruzan80

    Cruzan80 Mu-43 All-Pro

    Aug 23, 2012
    Denver, Co
    Sean Rastsmith
    For legacy lens (35mm), the "effective" focal distance changes due to the change in sensor size. What it is really doing is taking the center 50% as that is all it sees, so in terms of view, will appear the same as 2x the focal distance (aka. A 50mm legacy lens on a m4/3 will produce the same image as a 100mm lens on a 35mm camera). The aperture distance will remain the same (aperture values are mathematically derived by overall size of lens and size of opening). What will change is the depth of field effect (again due to relative sensor size). Shooting the same f2 lens on a m4/3 and 35mm will result in 2x depth of field on the m4/3. Hope this helps. People start getting in trouble when they start thowing around terms like "effective"focal without referencing what they are comparing. It sounds like Olympus was taking effective aperture as a shortcut for dof.
     
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  5. Vincen77o

    Vincen77o Mu-43 Regular

    123
    Nov 3, 2012
    St. Albans, Herts
    Good explanation re: the "effective" focal distance, this is how I've always understood it. What puzzles me is, the adapter must act like an extender. I've bought a Canon 50mm 1.4 plus cheap extender which is similar in size to a 1.4 extender. So, rather than act like a 100mm lens, wouldn't it be more like 130-140mm? I know the adapter hasn't got optics, but it is pushing the lens further from the sensor.
    When the lens arrives I'll shoot something like a brick wall with the 50mm, this way I can get the edge limits of the shots the same. Then I'll take the same shots using my 14-140 and see what that reads in the exif data. I may also be able to compare the DoF. I'll keep you posted.
     
  6. uci2ci

    uci2ci Mu-43 All-Pro

    Jun 22, 2012
    Los Angeles, CA
    Sam
    If you talking about an extention tube, then ur focal length will be the same and ur minimum focus distance decreases and you lose infinity focusing. If ur talking about a teleconverter, then u have a 140mm effective focal length. I've never heard of a 1.4 tc without optics
     
  7. The purpose of the adapter is to set the lens at the same distance to the sensor as it would have relative to the film plane on the camera it was designed for. By comparison, an extender will locate the lens further away from the sensor/film which increases the lens' magnification.
     
  8. arentol

    arentol Mu-43 Veteran

    269
    Jun 29, 2012
    Actually Cruzan80's explanation has some issues. It is actually much simpler than that:

    "A lenses focal length is the lenses focal length, period."

    It is entirely irrelevant what camera a lens was designed for, its focal length remains unchanged. If a CCTV system (security camera) lens says it is 12mm then it is 12mm. If a Large Format lens says it is 75mm then it is 75mm. If you compare the Angle of View (AOV) of the CCTV lens to they Olympus 12mm on your m4/3rds camera they will be the same. Same if you compare the large format lens to the Olympus 75mm. The format, the size, all that stuff is irrelevant, the focal length does not change.

    For the reason above there is no "effective" focal length. That is a very misleading way to put things because it implies that focal length is different in some way between camera systems, which it is not. "Equivalent" Angle of View or Field of View, on System (or format) X, would be the appropriate way of putting this because it is a term of comparison, and all you should ever be doing is comparing. But even this should be used sparingly because it can confuse people who are still learning. The core explanation above remains the most correct, because it really is that simple, and because anyone who doesn't seem to fully understand this, like rdo, needs to get that part 100% clear before moving on to things like "equivalent angle of view".

    As to your question, you are conflating three different pieces of equipment, Extension Tubes, Teleconverters, and Lens Adapters. I suggest you check out all three terms on Wikipedia, that should help straighten you out. I assume you ordered a lens adapter, so pay close attention to that article on Wikipedia. Also, remember what I said earlier, your 50mm lens will still be a 50mm lens. That does not change no matter what. It will just provide a field of view similar to that which a 100mm lens would on 135 (35mm). However, unless you think only in 135 terms when it comes to photography then that fact is almost entirely irrelevant to you.


    One more thing. Luckypenguin's explanation about extenders is misleading. Without going into too much detail (check it out on wikipedia), what an extender (extension tube) essentially does is decrease your minimum focus distance. This means you can focus while closer to your subject and therefore the subject is effectively larger. So it isn't the extension tubes "magnifying" things, it is being closer to the subject that magnifies things. Also, if you don't end up getting closer (perhaps because the subject is likely to move if you do), then the extension tube does nothing for you..... Teleconverters on the other hand do magnify things, so it can confuse people if you say extenders do so as well.
     
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  9. Vincen77o

    Vincen77o Mu-43 Regular

    123
    Nov 3, 2012
    St. Albans, Herts
    That's an excellent reply thanks. I'm off to do some more research and when the gear arrives I'll still do those tests, but more scientifically.
     
  10. That is the technical explanation, but in practical terms the only reason to use extension tubes is allow a lens to focus closer and achieve higher magnification ratios for macro photography.
     
  11. Vincen77o

    Vincen77o Mu-43 Regular

    123
    Nov 3, 2012
    St. Albans, Herts
    OK, Canon 50mm FD 1.4, adapter and hood all arrived today so went outside and did those tests. The lens was in excellent condition for £30 and the adapter was a good fit, no movement.
    I set up the camera looking at the garage wall using the 50mm first and put tape marking the left and right extremities. Starting at wide open I took a shot at each stop up to f22.
    I then put the 14-140 on, zoomed it to the tapes and repeated above. I also did the same with the 20mm 1.7 pancake, obviously moving the camera forward to match the width.
    The Exif data on the 14-140 showed 54mm so nothing dramatic proved there. The primes were both sharper than the zoom, expected. The 20mm gave the best result stopped down to 5.6, narrowly shading the Canon set at f4.
    I also took some bokeh test shots with the 50mm and zoom lens. At wide open the Canon is too much, but superb at f2, really pleased. Results posted here:

    50mm Test - a set on Flickr

    Conclusions. The 14-140 is a good all-round lens and I prefer it over the 45-200. Like many other people the 20mm is my favourite leave it on lens, but I'm well pleased with the 50mm, even the folding rubber hood fits well. I'm just waiting to snatch a good 70-210 from €bay and a 135.......
     
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  12. GaryAyala

    GaryAyala Mu-43 Legend

    Jan 2, 2011
    SoCal
    According to Wikipedia, extender and converter are interchangeable ...
    "A teleconverter (sometimes called tele extender) is a secondary lens which is mounted between the camera and a photographic lens. Its job is to enlarge the central part of an image obtained by the objective lens.?

    I've been shooting for decades, and this is the first time I've seen "extender" used when referencing macro extension tube sets. Typically, 'tubes' or 'extension tube' is the common description, not extender. Nic is correct.

    Gary
     
  13. arentol

    arentol Mu-43 Veteran

    269
    Jun 29, 2012
    I agree, and that is exactly what I said. What I am also saying is that it is very important to distinguish how these things work when trying to help people who are still learning. Otherwise you get situations where people have been told extension tubes magnify your subject and teleconverters magnify your subject and closeup lenses magnify your subject... So in their minds all three are doing the same thing. But they aren't, and in particular teleconverters are extremely different from the other two.
     
  14. arentol

    arentol Mu-43 Veteran

    269
    Jun 29, 2012
    If you read Nic's post to which I was responding when he mentioned "extender" he was VERY clearly describing how an extension tube works, not how a teleconverter works.

    Nic himself also responded to me and effectively admitted that we were talking about the same thing by the nature of his response.

    I am correct.
     
  15. dwig

    dwig Mu-43 Top Veteran

    623
    Jun 26, 2010
    Key West FL
    "Extension Tube" and "Teleconverter" are NOT interchangable terms. They refer to completely different attachments that are used for completely different results.

    Teleconverter and Tele Extender are, historically, interchangeable terms for the photographic equivalent of what telescope users refer to as a Barlow Lens. Teleconverters are a combination of a negative focal length lens, which increases the focal length of the lens it is attached to, and an extension tube which restores infinity focus. There were lens attachments made back in the days of bellows cameras ("view" and "press" cameras) which were negative FL lenses and relied on the camera's ability to extend the bellows to adapt to the new longer focal length. While the simple lens attachments date from the late 19th century, the "teleconverter" style of attachment was introduced into the photographic world in the late 1950s.

    Extension Tubes (aka "tubes") are just hollow tubes that move the lens further from the sensor/film to cause it to focus closer. They do absolutely nothing to increase, or decrease, the focal length of the lens to which they are attached.
     
  16. GaryAyala

    GaryAyala Mu-43 Legend

    Jan 2, 2011
    SoCal
    You are right, Nic did write extender in lieu of extension ... you should have corrected him (lol).
     
  17. GaryAyala

    GaryAyala Mu-43 Legend

    Jan 2, 2011
    SoCal
    If you are attempting to correct me, please read my post again. (I never said extension tube and teleconverter are interchangeable terms, in fact I clearly stated that Wikipedia claims the terms Teleconverter and Tele Extender to be interchangeable.)

    Gary
     
  18. Ned

    Ned Mu-43 Legend

    Jul 18, 2010
    Alberta, Canada
    Yes, that's what Gary was saying. :) Converter and Extender are the interchangeable terms, neither of which are interchangeable with Extension Tube.