Confused about mft lenses

Discussion in 'Native Lenses' started by Gary Thompson, Oct 9, 2017.

  1. Gary Thompson

    Gary Thompson New to Mu-43

    8
    Oct 9, 2017
    First off, hello everyone.
    I'm coming across from Nikon of which I've been a user for over 10years. I've been shooting full frame for the last 3 years and am switching to an Olympus OMD E 5mk2 (it's arrived at the shop and I'm very excited).
    I'm trading in my D750 body and a selection of lenses for a few MFT lenses.
    The problem is, I'm a bit confused as to why all the reviews state "XX full frame equivalent".
    I'm looking at the 60mm 1.8, 17mm 1.8, and 40-150mm 2.8 Pro.
    Every time I read a review, the reviewer, for example for the 60mm 1.8, will state 120mm ff equivalent (I see the crop factor on the mft is x2).
    Now. When I went to ff with my Nikon gear, I understood that I'd have to upgrade to ff lenses or I'd have vignetting using my DX (aps-c sensor) lenses. I also understood that going the other direction, ie. fitting an FX (ff) lens to a DX camera body would result in cropping, which I did quite a bit when using my old D80 and scouring eBay for older, non aps-c lenses.
    In this case with the Nikon, I can see why someone would say that a 30mm prime full frame lense on an aps-c would have an effective length of 75mm due to the 1.5 crop factor. Simply because the full frame lens is designed for a full frame sensor and the DX lens is designed specifically for an aps-c camera ( I won't go in to the distances from sensor to lens etc etc).

    So. After all that, if all the lenses I'm looking at are designed for the mft camera, why is everyone mentioning the X2 cropped ff equivalent?
    If I buy the 17mm 1.8 and pop it on my M5, am I expecting to see a true 17mm field the same way I'd pop on a 17mm on my D750? Or should I be expecting a field of view that I'd expect if I'd put a 34mm on to my d750? Basically, should every lens length that I look at be multiplied by 2 or not? If I use a 50mm on my Nikon and want the same view on the Oly, do I buy a 50mm mft or do I have to buy a 25mm to achieve the same viewing angle?
    Bit of a long post but the reviews have really messed me up a bit with these mft lenses.
     
  2. Powaysteve

    Powaysteve Mu-43 Regular

    42
    Jun 23, 2017
    Poway, California
    It is no different than your Nikon aps-c camera. In comparison to a full frame camera format the MFT Cameras are a 2.0 crop factor. That is why you see all those references
     
  3. marcsitkin

    marcsitkin Mu-43 Veteran Subscribing Member

    392
    Jan 24, 2013
    Harwich, MA USA
    Marc Sitkin
    Your mft lens field of views are equivalent to a 2x field of view on FF.
    A 25mm mft =50mm on FF, etc.
    Divide the FF focal length you like by 2 to get the mft equivalent.
     
    • Agree Agree x 2
  4. Powaysteve

    Powaysteve Mu-43 Regular

    42
    Jun 23, 2017
    Poway, California
    If yourD750 is a full frame camera and you use a 50mm lens then a 25mm lens on a MFT camera will provide the same field of view.
     
    • Agree Agree x 1
  5. Growltiger

    Growltiger Mu-43 All-Pro

    Mar 26, 2014
    UK
    Even more wonderful is that a 300mm lens on your new camera will give you field of view of a huge 600mm lens on the D750.
     
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    • Agree Agree x 1
  6. Aristophanes

    Aristophanes Mu-43 Regular

    It's about focal length equivalence and marketing to the "norm". We are still living in a legacy standard of 135 from the film era, translated to FF.

    The 17mm has an equivalent 135 focal length to a 35mm (or close enough; no manufacturer is right on with exacting focal length, especially for zooms...they round off).

    So yes, to get the fast fifty FL 135 equivalent on m43 you need a 25mm.

    And those measures entirely consistent across all m43. You either state the m43 focal length (e.g. 25mm) and the to get the 135 equivalent multiply 2x.

    Or vice versa; you take the 135 FL, say a 24mm wide angle prime, and halve that (x0.5) for a 12mm m43 equivalent.

    Aperture value is a whole different beast. That stays constant relative to iris size regardless of the "crop", but a smaller image circle increases the DoF. m43 requires half the dimensional image circle of FF aka 135. So an f/1.8 m43 lets in as much light as any other 1.8 relative to the image circle, but with a smaller image circle to begin with, the DoF increases. So the f/1.8 in m43 will have a deeper DoF than the 135 f/1.8. Readily measured here:

    Online Depth of Field Calculator
     
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  7. Gary Thompson

    Gary Thompson New to Mu-43

    8
    Oct 9, 2017
    Wow. Great response already. So I'm gonna have to train my eye again in the viewfinder.
    No problem, that has sorted my dilema. I'm all for the 600mm equivalent especially if the 5 axis IBIS is as good as they say. I'm a bit nervous though about finding a good wide angle prime. A 10mm prime on the ff would require me to source a 5mm prime for the mft or there abouts.
    Thanks for you help chaps. Hoping to get some snaps up here soon with the new toy.
    I'm currently in Italy on my hols and just returned from a piano recital. The D750 in quiet mode is very far from it. I had to ask to move myself to the rear of the room so as not to annoy the other listeners, even then, it was too loud and only managed 2 shots while the guy was playing, the rest of my images had to come whilst the audience was clapping to drown out the mirror slap. Hopefully the M5 will be much quieter.
     
  8. Aperture Don

    Aperture Don Mu-43 Veteran

    230
    Jan 7, 2017
    Illinois
    As a life-long Nikon FF shooter, I think that it's best to answer your last question first since I think that you have some misconceptions and misunderstandings about crop factor and field (or angle) view. So, if you want the same field of view that your 50mm lens gives you on your D750, you must buy a 25mm lens for your E-M5. That is because the crop factor is 2. When you used your FF 50mm on your D80, since the D80 is a DX format camera, the crop factor was 1.5, therefore the field of view from your 50mm lens was the same as a 75mm lens on that D80. The focal length of the lens does not change. The only thing that changes is the field of view. A 50mm lens is always going to be a 50mm lens.

    Something that you said is really not correct. "I also understood that going the other direction, ie. fitting an FX (ff) lens to a DX camera body would result in cropping." There was nothing wrong with using a FF lens on a DX body, in fact, you gained an advantage since the DX body was only using the center of the lens to fill that DX sensor.

    I hope this helps. It's really not that complicated but thinking about it too long only adds to the confusion.
     
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  9. nstelemark

    nstelemark Mu-43 Hall of Famer Subscribing Member

    May 28, 2013
    Halifax, Nova Scotia Canada
    Larry
    Personally I really don't think about the crop factor anymore. A 12mm lens is what it is, as is a 200mm. Since you can't mount these lenses on anything other than MFT (I suspect someone will find an example to prove this wrong but whatever :drinks:), I don't think that thinking about crop factor is really terribly useful.
     
    • Agree Agree x 6
  10. nstelemark

    nstelemark Mu-43 Hall of Famer Subscribing Member

    May 28, 2013
    Halifax, Nova Scotia Canada
    Larry
    The 8mm f1.8 fisheye is really truly spectacular. And the FOV is huge albeit not rectilinear.
     
  11. TheMenWhoDrawSheeps

    TheMenWhoDrawSheeps Mu-43 Veteran

    434
    Jun 15, 2016
    few more things to consider - m43 is also aspect ratio of 4:3 intead of FF 3:2 - so expect to have a bit more space to work within the frame. i had to adapt a few month until i finally got the composition right. also, try shooting more in portrait orientation - it´s quite a bit more satisfying.
    don´t treat your m43 gear as ff - first error you would probably do is photographing a landscape with f16, and complaining about lack of sharpness. just half the aperture as you half the focal length.
    most pro lenses are very good wide open, peaking performance at f5.6 or even f4. f8 is as far as i would ever go, and above f11 diffraction starts to kick in.
     
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  12. ralf-11

    ralf-11 Mu-43 Regular

    141
    Jan 16, 2017
    I think the first issue you will have is photographing a landscape, and complaining about lack of DR
     
  13. I shot a dress rehearsal in the Spring. I was two rows up and about 8 - 10' from the actors using my em5mkii and the 12-100/4 Pro. I took between 80 and 100 shots and apparently never bothered the actors at all. However another member of our photo club sat in the 3rd or 4th row and about 5 seats away from me... shooting with his Nikon, supposedly in silent mode and as you say from your own experience it was "very far from it"... so much so that it bothered me to the point where tried not to shoot when he was so that I wouldn't be blamed for his ignorance... yes, that's what it came across as to me so I imagine the others sitting around him were feeling the same!

    as I recall... I didn't even have mine set to silent mode... it was quiet enough as it was! I think you're going to enjoy yours too!

    Welcome to the forum... you're in the right spot imho! :2thumbs:
     
  14. ralf-11

    ralf-11 Mu-43 Regular

    141
    Jan 16, 2017
    I have a related question...

    when I look at the EXIF in a mac using the Finder - one photo says the Focal length is 25 mm. Is that the m43 25mm or the FF equivalent? From the barrel distortion I assume it is the later, FF Eq. not something that would be doubled to yield a normal lens...
     
  15. nstelemark

    nstelemark Mu-43 Hall of Famer Subscribing Member

    May 28, 2013
    Halifax, Nova Scotia Canada
    Larry
    It has to be the actual focal length. This is why equivalency and the discussion of equivalency is really quite tricky. A 25mm lens is a 25 mm lens is a 25mm lens, it is not anything else. The FOV will change assuming you could mount it on a different sensor and the image circle would actually illuminate the sensor but it would still be a 25mm lens.
     
    • Agree Agree x 1
  16. ralf-11

    ralf-11 Mu-43 Regular

    141
    Jan 16, 2017
    seems like it is but the Apple Finder knows the lens F/L, and the camera even to its s/n, so could present a conversion

    too bad out grandparents didn't just use angle of view all the time...
     
  17. That's what I'm getting too... just used my 12-100/4 at 100mm for some "bug" shots and looking at the file in RAWPower they show as 100mm... cmd-I in the finder doesn't show the focal length on my mac, but shows everything else
     
  18. Aristophanes

    Aristophanes Mu-43 Regular

    Through the VF, the m43 image of a 25mm lens will look identical to a FF 50mm lens.
     
  19. PakkyT

    PakkyT Mu-43 All-Pro

    Jun 20, 2015
    New England
    It is tough to recommend a micro four thirds equivalent to a lens that does not exist. Do you have an example of a full frame 10mm lens that isn't a fisheye that you would like to replicate in m43rds?
     
  20. Aristophanes

    Aristophanes Mu-43 Regular

    10mm on FF is ultra wide and exceedingly rare. 12mm, as in The 12–24/2.8 for Nikon, is considered very wide. I think 8mm on APS-C is the widest I have seen rectilinear. All the 7mm photos on m43 I have seen are outstanding.