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Would the 40mm Olympus Pen F lens still have the focal length doubled on mft cameras?

Discussion in 'Adapted Lenses' started by colbycheese, May 29, 2015.

  1. colbycheese

    colbycheese Mu-43 Veteran

    378
    May 1, 2012
    Way up there.
    I was wondering this. even though the pen f cameras used half frames, would the focal length still double like any other legacy adapted lens? I assume so but i want to make sure before i purchase one. Another way of wording it is, what would the fov on the m43 cameras be compared to the olympus pen f?
     
  2. edmsnap

    edmsnap Mu-43 Veteran

    430
    Dec 20, 2011
    Edmonton, Alberta
    Focal length has nothing to do with the sensor; it is exclusively a mathematical optical property of a lens. A 40mm lens will produce the same field of view as any other 40mm lens will on whatever sensor you put it in front of.
     
  3. RnR

    RnR Mu-43 All-Pro

    Sep 25, 2011
    Brisbane, Australia
    Hasse
    Just in case edmsnap's answer was not clear... yes. Always x2 - irrespective of where the lens comes from. Half-frame, full-frame, medium-frame... always x2 for m43 camera's.
     
  4. tkbslc

    tkbslc Mu-43 Hall of Famer

    Your question is a bit odd, because if you don't double half frame camera lenses, why would you double our native 1/4 frame m4/3 lenses?
     
  5. pdk42

    pdk42 One of the "Eh?" team

    Jan 11, 2013
    Leamington Spa, UK
    All this doubling babble is simple really...

    A lens of focal length "x" will give approximately the same field of view on a four thirds sensor as a lens of 2 * "x" on a 135 (FF) sensor.
     
  6. David A

    David A Mu-43 All-Pro

    Sep 30, 2011
    Brisbane, Australia
    A more complete explanation:

    The focal length determines the field of view of the lens and that has nothing to do with sensor size. The lens projects an image circle into the camera and the sensor captures some of that image circle. The sensor captures a rectangle centred on the centre of the image circle. A bigger sensor captures more of the area of the image circle and a smaller sensor captures less of it. Regardless of sensor size, the centre of the sensor is always at the centre of the image circle so the smaller sensor captures an area at the centre of the larger sensor and how large that smaller area is depends on how much smaller the small sensor is compared to the large sensor.

    Nothing about the lens and it's image circle changes when you use a lens of a given focal length on a camera with a different sized sensor, what changes is simply how much of the image circle falls on the sensor. The rest of the image circle just doesn't get captured. If you print the image you would capture using a full frame sensor and compare that to an image printed from what you capture with an M43 camera using the same lens, you find that the M43 camera has only captured the central portion of the full frame image so the M43 image is what you would get if you took the full frame image, cropped the edges and retained only an area at the centre of the full frame image. That's why this 2x equivalence ratio is often called a "crop factor".What the M43 camera captures is essentially a quarter of the area captured by the larger full frame sensor. If you wanted to capture just the same area captured by the M43 camera but using a full frame camera you would need to use a longer focal length lens, effectively "zooming in" on that central area of the original frame, and you would double the focal length in order to capture just that area.

    The Pen F was a half frame camera so it also has a smaller sensor than a full frame camera but it also has a larger sensor than the M43 camera. I don't know what the equivalence or crop factor is for half frame cameras but at a guess I'd say it's around 1.41 (the square root of 2) based on the fact that the sensor area is half that of the full frame camera. On that basis the focal length of a lens on a full frame camera that would be equivalent to a 40 mm lens on the Pen F would be roughly 56 mm and if you want a comparable focal length for the Pen F sensor compared to an M43 sensor you would multiply the focal length by 1.41.

    In other words a 40 mm lens on an M43 body will give you the equivalent of roughly 56 mm on the Pen F and 80 mm on the full frame camera. A 40 mm lens on the Pen F would give you the equivalent of 56 mm on a full frame sensor or 28 mm on an M43 sensor.




    So, the following equivalences apply:

    Pen F to full frame: multiply the focal length on the Pen F by 1.41 to get the equivalent focal length on full frame and divide the focal length on full frame by 1.41 to get the equivalent focal length on the Pen F

    Pen F to M43: divide the focal length on the pen F by 1.41 to get the equivalent focal length on M43 and multiply the focal length on M43 by 1.41 to get the equivalent focal length on the Pen F.

    M43 to full frame: multiply the focal length on the M43 by 2 to get the equivalent focal length on full frame and divide the focal length on full frame by 2 to get the equivalent focal length on M43.
     
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  7. dwig

    dwig Mu-43 Top Veteran

    621
    Jun 26, 2010
    Key West FL
    Wrong. FL determines the size of an object in the image, it does not determine the FOV on its own. FOV can be determined only when you factor in the sensor/film size.


    Incorrect as worded. If you substitute "field of view" for every "equivalent focal length" is would be correct. It is this type of misswording that leads to the confusion like that of the OP.
     
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  8. dwig

    dwig Mu-43 Top Veteran

    621
    Jun 26, 2010
    Key West FL
    Focal lengths never change without adding some optical accessory. Your confusion comes from the common poorly worded explanations of the field of view differences that occur when a lens is used on a variety of different size sensors or film.

    The "2x" crop factor refers to the angle of view difference that a lens of a given FL yields between the "standard" 35mmFF film image size and that of the m4/3s sensor. It actually references the diagonal angle of view which is only an approximate measure of the field of view differences when considering formats that don't have matching aspect ratios (e.g. 35mmFf=3:2 while m4/3=4:3). Proper wording is something like "a 50mm lens used on m4/3 format yields approximately the same field of view as a lens of twice that focal length used on a 35mmFF format camera". The actual focal length doesn't change and all other properties involving focal length are either unchanged or have independent scaling factors.

    A 40mm lens from a Pen F half frame, when used on a m4/3 body, will give the same FOV as any other 40mm lens used on an m4/3 body and yielding about the same FOV as an 80mm lens used on FF and about the same FOV as a 56mm lens on a half frame Pen F.
     
  9. David A

    David A Mu-43 All-Pro

    Sep 30, 2011
    Brisbane, Australia

    You're right, and you're wrong.

    You're right that FOV can only be determined when you factor in the sensor/film size.

    You're wrong in assorting that I "misworded". I'm not even certain what "miswording" means but whatever it means I didn't do that. I misthought and then accurately reported my misthinking. :)

    That admission over, I could argue that I neither "misworded" or ""misthought". If you go back and read what I wrote you'll see that I said that the lens projects an image circle and that the sensor captures more or less of that image circle based on sensor size. I was considering "field of view" in the context of what is included in the image circle and it is solely the focal length which determines. The field of view of the lens can accurately be said not to change. The field of view which is captured by the sensor is, as you point out, determined by the combination of both focal length and sensor size. I referred to the FOV of the lens based on image circle and you referred to the FOV of the lens/sensor combination based on what gets captured by the sensor.

    I can also argue that the focal length does not determine the size of an object in the image. What it determines is the size of the object which is projected onto the sensor. The image is what you eventually end up with after you've processed the sensor data and the image can have different sizes depending on how large you print or display the image in its final form. You determine the size of the object in the image when you make your decisions about how much of the original frame you are going to include in the image (cropping decisions) and how large an image you are going to display. Sensor size is fixed but image size does not depend on sensor size. You don't have an image until you display it and display choices determine the size of an object in the image, not the focal length and sensor size.

    But I'm not going to argue either of those things. I'm simply stating that it's possible to do so, not asserting that one way is better or more accurate than the other. Talking about this sort of thing is messy. I sometimes wonder whether it's possible to say anything at all without first stating definitions for every term you're going to use and then adding a disclaimer that whatever you said is only going to be correct if the reader/listener accepts and applies the definitions you have stated to the terms you use. Neither of us defined the terms we used. We just used them in the way we thought was appropriate for what we wanted to say and we have each used terms in ways that the other doesn't think of them.

    We both know what we're talking about and we're both coming at the issue from different angles and backgrounds so we describe exactly the same phenomenon in different terms. From our individual perspectives each of us is right and neither of us disagrees about what's going on. We're just describing it in different ways. The problem is which way of saying it is going to help the OP most. You said that my miswording leads to the kind of confusion the OP was suffering from. It may but I'm not certain that it does. The way I described things may actually work for him, or it may not. Your way may work for him or it may not. One thing is certain and that is that he was confused before I responded and he was trying to resolve his confusion by asking a question. I tried to explain things in a way which I hoped would dispel his confusion but I certainly wasn't trying to write the kind of description which would score points for a brilliant exposition of a technical point. I was aware that I was glossing over some things but I was hoping to increase understanding at a practical level, not provide precise technical knowledge. I may well have stated things differently if he'd asked the question in a slightly different way or received different earlier responses.

    I hope my response helped the OP. If it didn't I hope your response might have made mine clearer and resolved his confusion for him. It's possible that neither of us have achieved what we desired in which case he has the option of coming back and asking more questions in which case we can try and explain things further but at the end of the day I'm not overly concerned about whether or not he can stand up in front of a class and describe what's going on in precise technical terms. What I'm concerned about is simply helping him to achieve a good enough appreciation of what's going on to make it easier for him to navigate the practical issues of choosing lenses on the basis of what he wants to achieve with them regardless of whatever size format they were originally intended to be used with and whatever size format he wants to use them with. That's really all I'm concerned with. In this case the only opinion which counts for me is that of the OP. Does he feel more confident about how to choose lenses from different camera formats now or doesn't he? I'd like him to be able to make the right choices. I'm far less concerned about whether or not his technical understanding is up to a particular level or not.
     
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  10. pellicle

    pellicle Mu-43 All-Pro

    Feb 10, 2010
    Southport, OzTrailEYa
    pellicle
    Hi

    Rembering that the pen was a half frame camera not a full frame one. The images will look quite similar between the pen film and the m43.

    Forget about doubling just put a lens on your camera and observe what it does and remember that. Doubling and whatnot is confusing and only meaningful to people so totally embedded in 35mm film as to be unable to see things any other way.

    For instance on my 4x5 sheet film camera 75mm is ultra wide and mid tele on my 35mm and tele on 43

    Just play and learn not read and attempt to learn and wind up not really *knowing* anything.


     
  11. David A

    David A Mu-43 All-Pro

    Sep 30, 2011
    Brisbane, Australia
    Not true. The Pen was half frame but M43 is really quarter frame. There is as much difference between M43 and the Pen as there is between the Pen and full frame.


    That's certainly one way of doing things and it does work for some people. There are also other people who want to understand why things work the way they do as well as what they do, and understanding that sort of thing can help them to get better results. What counts is what produces the desired outcome and different people learn how to obtain that desired outcome in different ways.
     
  12. dwig

    dwig Mu-43 Top Veteran

    621
    Jun 26, 2010
    Key West FL
    +1
     
  13. dwig

    dwig Mu-43 Top Veteran

    621
    Jun 26, 2010
    Key West FL
    I still contend that you erred in your summary in using the phrase "equivalent focal length" when the equivalence is with the field of view. It is the simplified wording, like that which you used, that is the root cause of the pervasive misunderstanding so many new users have. True, the correct wording is somewhat lengthy and it is human nature to take shortcuts, but such shortcuts damage communication.
     
  14. pellicle

    pellicle Mu-43 All-Pro

    Feb 10, 2010
    Southport, OzTrailEYa
    pellicle

    True, but I dont see much evidence of that. Anyway theory and practice go hand in hand. Sitting around all day debating theory seldom seem to trickle through to actual understani in many people.

    I started developing film and learning about 4x5, 6x9 and 35mm long long ago. I never even thought about equivalent lenses other than ball park stuff (this is wide, is is normal, is is tele) until digital came along and folks got themselves all tangled up with the numbers. So far I have yet tuk see tangible benefits in any discussion in this topic to the asker.


    Agreed
     
  15. David A

    David A Mu-43 All-Pro

    Sep 30, 2011
    Brisbane, Australia
    Personally I don't like "equivalent focal length" any more than you appear to do, and it most certainly is simplified wording. It does have one advantage, however, and that is that it gives a person a piece of information they can use in order to easily identify a lens that is doing the "equivalent job" if you like. After all, the focal length is written on the lens barrel so if you say to someone that the "equivalent focal length" is 80 mm, they do know what you're talking about. If you tell them the equivalent "field of view" is that of a lens with twice the focal length that was intended for use on a full frame body they're just as likely to end up more confused than less confused.

    If you want to continue this discussion, then start another thread for this discussion. What we're discussing here is not about what the OP asked but about other things, certainly related things, but things that the OP and many others who read this thread may have no real interest in pursuing. Alternatively, if what I wrote was so wrong and so objectionable to you whether in the facts I presented or the terminology I used, you're quite free to write your own response and say things exactly the way you want to say them. The practical effect of your answer will be exactly the same as mine.

    I made a choice about how much I wanted to put into my explanation and I said what I said on the basis of that choice. As I said previously, it's a messy area to talk about to someone who doesn't understand what's going on. I like having enough knowledge to understand at least the start of the technicalities but in my experience most people aren't interested in that level of knowledge. They just want enough knowledge to be able to deal with the practicalities and make the right choices. I wanted to give a bit more detail than a simple yes which would have given the OP the answer he was after, at least for all practical purposes, but I didn't want to go into the level of detail required to ensure he understood all of the principles involved and what the correct technical terminology was and how to use that in the most precise way. I was concerned that I might even be getting too technical for the OP when I wrote my response but, for better or worse, I tried to strike a middle ground and I wasn't chasing technical precision of terminology. I'm happy with some people disagreeing with my choice, I wasn't trying to satisfy everyone, especially anyone who understands the technicalities. I was trying to help one person who didn't understand the technicalities, and I was trying to help him in relation to the practical issues rather than the technical and theoretical ones.
     
  16. David A

    David A Mu-43 All-Pro

    Sep 30, 2011
    Brisbane, Australia
    Agreed. I started out with 35mm and was just interested in what was standard, wide, and tele when I started getting into M43. I only got interested in this whole topic of equivalence in terms of factors applied to focal lengths when I started seeing discussions about it here and had difficulty understanding what was being said a lot of the time.
     
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  17. pellicle

    pellicle Mu-43 All-Pro

    Feb 10, 2010
    Southport, OzTrailEYa
    pellicle
    Hi

    I often wonder if people ask these questions to see the usual fights about the thickness of a hair and how it can be split.

    Let me ask you a question or two

    1) did you know that a 40mm is a 40mm, it makes not the slightest whip if its a Sigma Art series for m43 or a Schneider for 645 ... you will still see exactly the same image (forgetting Bokeh) on a m43 camera irrespective which 40mm lens you put on.

    2) do you know intimately what the view of a printed (or scanned) image from an Olympus Pen camera looks like with the 40 or were you just thinking it was somehow a magic thing?

    3) have you looked on Flickr to see examples to see if you like the look of the lens (for the money)?

    Myself I'd be inclined to get a Konica Hexar 40mm f1.8 ... more lens for the money, more moden coatings exactly the same focal length which will make exactly the same image on your m43 sensor...

    Best wishes
     
    Last edited: May 31, 2015
  18. demiro

    demiro Mu-43 Hall of Famer

    Nov 7, 2010
    The problem isn't the OP. It's the fact that someone can't just answer "yes" to him. Too many people want to prove how much they know. You all know what he is asking. Just tell him "yes".
     
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  19. pellicle

    pellicle Mu-43 All-Pro

    Feb 10, 2010
    Southport, OzTrailEYa
    pellicle
    probably (but over the years I've noted an absence of followup from the OP in such threads) ...

    anyway, "the simple answer of yes" is why I answered as I did in my first reply to the OP. The OP doesn't seem to be a total newbie, so he knows enough to have grokked my reply :)
     
  20. RnR

    RnR Mu-43 All-Pro

    Sep 25, 2011
    Brisbane, Australia
    Hasse
    I thought I did... but maybe there was still too many words involved... :D