1. Reminder: Please user our affiliate links to get to your favorite stores for holiday shopping!

Help clarifying the effects of the NEX 1.5 crop factor using my legacy Canon FDn lenses

Discussion in 'Adapted Lenses' started by roundball, Sep 28, 2014.

  1. roundball

    roundball TalkEmount Hall of Famer

    Oct 8, 2013
    USA
    On and off during the 15 months I've been using Canon FDn lenses on an NEX-7 and getting up to speed with helpful information from various photography forums, I've seen various comments about the effects of the NEX 1.5 crop factor on legacy lenses.
    But I never seem to be able to get a clear understanding of it...and no longer have Canon 35mm film cameras to run comparison tests.

    Some comments state actual focal length / image magnification of the subject occurs.
    ie: The subject image in my FDn 200mm now appear as viewed through a FDn 300mm lens on a normal 35mm film camera.

    Other comments state only the 'field-of-view' is affected...narrowed.
    ie: the FOV of my 200mm is narrowed down to that of a 300mm on a normal 35mm film camera...but the subject image is not larger.

    If somebody can once and for all clarify this with absolute certainty, I'd sure appreciate it.
     
  2. xXx1

    xXx1 TalkEmount All-Pro

    Jan 15, 2013
    Focal length does not change. Crop sensors just take a small part of the film so the field of view is much narrower and lenses seem to to be much longer.
     
    • Like Like x 1
  3. Poki

    Poki TalkEmount Hall of Famer

    Aug 30, 2011
    Austria
    Of course the actual focal length doesn't change, only the field of view does. However, this does NOT mean that there's a difference in the resulting image from shooting a 200mm lens on APS-C or a 300mm lens on 35mm sensors. The compression and field of view will be the same, so you won't be able to spot a difference based on what's on the image. Depth of field is another topic - a 200mm f/4 lens on APS-C will have a less shallow dof than a 300mm f/4 on a 35mm sensor, i.e. it will be roughly equivalent to a 300mm f/5.6 in terms of dof.

    Also, don't forget that 35mm is not some magical reference format - a lens is not better or worse on smaller or bigger sensors than what full frame offers.
     
    • Like Like x 1
  4. José De Bardi

    José De Bardi Assistant in Virtue

    Aug 31, 2013
    Dorset, UK
    José
    Well it's kinda both...

    imagecircle35mmAPS-C_zps9e3429d1.

    If the red is the 35mm legacy lens image circle, and the green is the size of a 35mm film/sensor, and blue an APS-C sensor.

    As you can see, clearly the FOV is going to be narrower on the APS-C camera, and this has an effect of making a 200mm lens on an APS-C seem like the focal length of 300mm on a Full Frame... So while no magnification is technically occurring it looks like it has been.
    It's called a crop fact as you are literally cropping the image circle.
     
    • Like Like x 2
  5. davect01

    davect01 Super Moderator

    Aug 20, 2011
    Fountain Hills, AZ
    Dave
    Good info. This matters alot if comparing lenses on various systems.

    However for me, the NEX-6 is the only camera I own and I don't really worry to much on what my lens would look like on other systems.
     
    • Like Like x 1
  6. Dan Euritt

    Dan Euritt TalkEmount Regular

    191
    Jan 11, 2014
    the reason that some people claim that crop sensors give more "magnification" over ff, at the same focal length, is because some crop sensors have higher pixel density than any ff sensor currently does.

    my understanding is... given the same focal length, more crop sensor pixels equals a bigger picture on your computer, but the field of view will be the same as a ff sensor that's been cropped to aps-c size.

    of course, wrt ff vs. crop, higher pixel density typically equals worse iso performance, lower latitude and d.r., etc... so it's all a big tradeoff.
     
    • Like Like x 1
  7. Poki

    Poki TalkEmount Hall of Famer

    Aug 30, 2011
    Austria
    The pixel density indeed is higher, but the absolute pixel count is not (most of the time). So a photo from a NEX-7 will have the same 6000 x 4000 pixels a photo from the A7 has.

    The only time when magnification actually is different is when using a macro lens at macro distances. A 1:1 macro lens can fill the frame with a 36 x 24 mm subject on ff, but on APS-C, it only requires a 24 x 15,3 mm subject.
     
    • Like Like x 1
  8. Dan Euritt

    Dan Euritt TalkEmount Regular

    191
    Jan 11, 2014
    only because they are both 24mp sensors; but that doesn't really matter, because the nex-7 has higher pixel density than even the a7r has.

    given the same focal length... if you crop a7/a7r photos to match the nex-7 aps-c sensor size, they will have the same fov as the nex-7, but fewer pixels, so at 100% view on the computer, the nex-7 will be a bigger picture, because it has more pixels.

    the argument for crop sensor "magnification" is really a pixel density argument.
     
    • Like Like x 1
  9. Poki

    Poki TalkEmount Hall of Famer

    Aug 30, 2011
    Austria
    Sure, but again, you should consider lenses with equivalent field of view, because anything else is just not relevant. And in that case, there's no difference.
     
    • Like Like x 1
  10. roundball

    roundball TalkEmount Hall of Famer

    Oct 8, 2013
    USA
    Thanks all...this is close enough to validate my experiences which were that the field of view did seem a little more narrow and the main subject never looked any larger through the lens.
     
  11. chrid

    chrid Super Noob

    807
    May 5, 2014
    australia
    Chris
    I was under the impression that a 1:1 macro lens is still 1:1 on apsc, as in if you used full frame to capture something 35mm across that fills the frame that is 1:1 on apsc if the subject is 24mm across it should still fill the frame thus still being 1:1
     
    • Like Like x 1
  12. rdfisch

    rdfisch TalkEmount Regular

    180
    Nov 13, 2013
    Northern NJ
    Rick
    Help clarifying the effects of the NEX 1.5 crop factor using my legacy Canon ...

    I think I understand the above discussion when it comes to pixel count and density, but let's look at this from a non-technical lay-person point of view.

    Consider viewing a sooc image captured with a NEX sensor on a maximized window on your display. Since the field of view is narrower, the subjects in the image appear larger on the screen than they would if the corresponding image from a full frame sensor were displayed in the same size window, hence the feeling the subjects are "magnified". (Substitute "printed on the same size paper" or "displayed on the same size EVF/LCD" for "displayed in the same size window" if you wish, and by size I mean absolute measure, not pixels.)

    Technically the image from the NEX sensor has been stretched (or condensed less) to fit the same display area, but from a lay point of view I can see why it may be regarded as magnified. I think this is just a restatement of the pixel density argument in practical/lay terms.

    Considering the above, I think that the subject WOULD appear larger, if the comparison could be made between a NEX & FF that had similarly sized EVFs or LCDs (again measured in mm, not pixels).

    It's late and I should be asleep already ... I can't even think about the 1:1 macro facet of this discussion, but aside from that is my analysis correct ?
     
  13. chrid

    chrid Super Noob

    807
    May 5, 2014
    australia
    Chris

    If you really want to stir the bee hive you can bring up the crop factor and multiplication of f stops :rolleyes:
     
  14. roundball

    roundball TalkEmount Hall of Famer

    Oct 8, 2013
    USA
    And I thought I took pains to make my original question as plain and simple as possible.
    :biggrin:

    Put another way:
    A 200mm lens on my NEX-7 doesn't make the subject suddenly jump up larger as if I'd just mounted a 300mm lens.
     
  15. rdfisch

    rdfisch TalkEmount Regular

    180
    Nov 13, 2013
    Northern NJ
    Rick
    Keeping it short doesn't necessarily make it plain/simple, but often makes it ambiguous.

    Viewed how (through viewfinder/on LCD, on monitor, printed) ?

    Compared with what (looking through the same lens on a FF, looking through a different FL lens on the same APS-C camera) ?
     
  16. roundball

    roundball TalkEmount Hall of Famer

    Oct 8, 2013
    USA
    LOL...

    ".....and the main subject never looked any larger through the lens....."
     
  17. ChangshaNotes

    ChangshaNotes Super Moderator

    Aug 15, 2012
    China
    Colin
    I currently own a NEX 7, so if I buy an A7, does that mean that in portraits my wife won't be as fat? :p
     
  18. chrid

    chrid Super Noob

    807
    May 5, 2014
    australia
    Chris
    She will also be shorter ;D
     
    • Like Like x 1
  19. WoodWorks

    WoodWorks Super Moderator

    Dec 12, 2012
    Ashland, OR, USA
    David
    No but if she reads this, your head will be. :p
     
    • Like Like x 1
  20. ChangshaNotes

    ChangshaNotes Super Moderator

    Aug 15, 2012
    China
    Colin
    Haha, If she reads it, I'm ok. If she get's it translated.... I'm dead.
     
    • Like Like x 1