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Verification of NEX-7 1.5 crop factor effect

Discussion in 'Sony Alpha E-Mount Cameras' started by roundball, Oct 29, 2013.

  1. roundball

    roundball TalkEmount Hall of Famer

    Oct 8, 2013
    USA
    Trying to get a definitive answer to this.
    My understanding is that when I mount my Canon FD 300 lens for example, the 1.5 crop factor narrows down the angle of view as if it was a 450mm lens...but the magnification remains the same at 300mm focal length.
    Or said another way, simply mounting it on a NEX-7, the crop factor does not take the place of a 1.5 Tele-converter, correct?
     
  2. raay

    raay TalkEmount Regular

    58
    Sep 1, 2013
    What do you mean by magnification remaining same ?? the focal length of the lens will be same ,the image circle produced by the lens is not completly seen via the APS-C sensor, you only see the APS-C frame!!!

    the effect is similar to mounting you 300mm fd lens with a 1.5x TC on a fd body ,but without the associated lightloss of the FD teleconverter , so the equivalent focal length of you 300 mm lens On the NEX 7 will be 450mm
     
  3. xXx1

    xXx1 TalkEmount All-Pro

    Jan 15, 2013
    Yes. Crop factor is pretty good term, with crop factor camera you crop some of the image off.

    This isn't as bad as it sounds. Old lenses have usually significantly better center performance and modern sensors are very good. The real nuisance is really the cropping, you may need a wider lens.
     
  4. quezra

    quezra TalkEmount Top Veteran

    916
    Aug 22, 2012
    The angle of view does change through cropping, as what is 'missed' at the crop edges is proportionate to the total frame throughout. Wikipedia explains this quite well with this illustration:
    LensCropFactor.

    The magnification is indeed the same, but because crop sensors usually tend to have more pixels per square inch, it allows for more 'magnification' because the pixel sites are finer. So on the 24 megapixel NEX-7, you'd need at least a 54 megapixel full frame camera to match the pixel resolution (basically 24 x crop factor^2 - in this case 2.25 times) so there's a 'virtual' magnification by the higher real resolution on the crop sensor. The 36 megapixel A7r would exactly match the 16 megapixel NEXes, meaning if you shoot with the A7r and did a 1.5 crop, you would get exactly the same image as you would on a regular NEX-3/5/6 camera (i.e. there's no virtual magnification in this case).
     
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  5. Amin Sabet

    Amin Sabet Administrator

    Aug 6, 2011
    For all practical purposes, it's almost exactly the same as a 1.5x teleconverter in terms of final image produced. The effects on total light collection, angle of view, depth of field, etc etc.
     
  6. roundball

    roundball TalkEmount Hall of Famer

    Oct 8, 2013
    USA
    Thanks for the replies so far...and the Wikipedia view is exactly my understanding.
    But the part that still seems a little like wrestling with a greased pig, LOL, is the enlargement / magnification from the telephoto effect...300mm vs. 450mm.

    Please ponder this question with me:
    If I put my Canon FD 300mm on my Canon A1 SLR, and view a 1 foot square at 50yds lets say, it'll appear as a certain "size" in the center of the lens lets say.

    Then, all other things being equal, if I then simply move that 300mm lens over to the NEX-7, will that same 1 foot square object then be 1.5 times larger in the center, instead of the original 1 foot in size?
     
  7. raay

    raay TalkEmount Regular

    58
    Sep 1, 2013
    exactly!!!----- lets say you are using a 50mm lens on your Fullframe film slr ---- now you are standing 10 feet away from a person and you can shoot from his head to toe in a photo , now if you put evrything constant and only change your camera to a APS-C camera you will find you cannot frame the person from head to toe!!!!
     
  8. raay

    raay TalkEmount Regular

    58
    Sep 1, 2013
  9. roundball

    roundball TalkEmount Hall of Famer

    Oct 8, 2013
    USA
    Wife getting X-rays, will check videos soon, thanks.

    So if it all works this way, the squirrel I recently shot with that Canon FD 300 + Canon FD 2X TC actually had the magnification power of a 900mm lens...
     
  10. raay

    raay TalkEmount Regular

    58
    Sep 1, 2013
    exactly!!! :biggrin::biggrin:
     
  11. roundball

    roundball TalkEmount Hall of Famer

    Oct 8, 2013
    USA
    Does it follow that the Canon FD 300 is a f4.0L, times 2X = f8.0, times 1.5 = f12 ??
     
  12. raay

    raay TalkEmount Regular

    58
    Sep 1, 2013
    I dont think that Aps-c sensor crop has anything to do with light loss, the light reaching the sensor is same ,but in dof terms it might be F12 ,this is because with the fullframe sensor the lens will act how it was designed ,but with a crop sensor if you have to make the same framing you will have to move back a few feet to make the same framing ,thus increasing the dof ,so In dof terms it will be F12 but in light terms it will still be f8, i strongly advice to see the video links i have posted ,i think you will get the idea!!
     
  13. xXx1

    xXx1 TalkEmount All-Pro

    Jan 15, 2013
    But to make same size enlargement you have to enlarge more and blurriness increases.
     
  14. raay

    raay TalkEmount Regular

    58
    Sep 1, 2013
    not necessarily ,the Aps-c sensors are more densely packed than fullframe senors,this have been pointed out earlier on this thread!!!
     
  15. roundball

    roundball TalkEmount Hall of Famer

    Oct 8, 2013
    USA
    Will watch them later today for sure.
    Frankly I've been skeptical of the magnification claim but enough folks on a couple forums now claim it to be the case.
    Just been hard to accept that while carrying Aron an excellent Canon FD 200/2.8 it's really a 300/4.0
     
  16. raay

    raay TalkEmount Regular

    58
    Sep 1, 2013
    aps-c always gives magnified view !! I am shocked that you dont know this!!!!!!! :O :O :O
     
  17. roundball

    roundball TalkEmount Hall of Famer

    Oct 8, 2013
    USA
    Was heavy into photography all through th 80's...then got away from it chasing a career, now retired and just got back in a couple months ago with the NEX-7...getting up the learning curve now.
     
  18. roundball

    roundball TalkEmount Hall of Famer

    Oct 8, 2013
    USA
    Decided I’d run some tightly controlled side-by-side tests, to try and see first-hand, the effects of the NEX-7 1.5 “crop factor” on the “magnification” of an image, using the following:
    Canon A1 SLR with Canon FD 70-150 lens.
    Sony NEX-7 / FD adapter, and same Canon FD 70-150 lens.

    Made a simple test board with the rows of target stickers. (below)
    Set up a permanent camera body location platform for the test repeatability
    Marked the exact rear location of the lens mount on the camera platform to standardize it
    Zoomed the test paper up to fill the viewfinder to the edges
    Shot the identical lens settings and location from the SLR and the NEX-7

    The Canon A1 SLR viewfinder was filled with the target test paper on the left (below).
    The NEX-7 viewfinder was filled with the target test paper on the right (below).
    (note top row of stickers is missing from the NEX-7 image)

    CONCLUSION FROM THIS SIMPLE TEST:
    The target paper measured 6.5” x 6.5” square.
    The NEX-7 did indeed crop off some of the image size…but nowhere near half of it, subsequently the resultant image magnification was nowhere close to 1.5 times larger.

    Test conditions were standardized as humanly possible for me to do so. Others may run more scientific tests of course…but we’re not talking about decimal point size differences here, not splitting hairs…the tests I ran showed that the effects of the 1.5 cropping factor wasn’t even close to being magnified 1.5 times larger.
    And to be honest, whenever I mounted one of my Canon FD lens on the NEX-7… that I’d spent many years behind on Canon SLRs…other than the slightly more narrow angle of view through the EVF on the NEX-7…I NEVER had any sense of “Wow, this lens is suddenly now MUCH more powerful than ever before”.

    NOTE:
    If I’m overlooking some flaw in my testing approach that would make my results incorrect and account for getting the results that I did, I’d appreciate the feedback as I’m only interested in the facts.
    Meanwhile, reference the images below: Left was Canon A1…..Right was NEX-7

     
  19. quezra

    quezra TalkEmount Top Veteran

    916
    Aug 22, 2012
    You misunderstood - there is no magnification in real terms - i.e. your images should be identical in size between digital and film. The 'virtual' magnification comes from the fact that the NEX-7's pixels are much smaller than a NEX-6 or A7r and so when you set both to 100% crop (i.e. equalize the size of pixels in both), the 7's image will be larger. But in proportion to the size of the sensor, there is no difference - if you print both a NEX-6 and 7 to 4x6 all will be equal in size of course.

    Sent from my GT-I9505 using Tapatalk
     
  20. roundball

    roundball TalkEmount Hall of Famer

    Oct 8, 2013
    USA
    Finally...straight talk and that's been my feeling all along !
    I know the NEX-7 has a terrific ability to crop heavily after the fact, and still maintain excellent IQ due to its sensor...but I simply could not get comfortable with the idea that simply mounting a lens on an NEX-7 magically increased it's tele-photo power as a number of individuals in multiple threads seem to think it does.