No mention of crop factors

Discussion in 'Digital Photography' started by E3BK, Apr 24, 2017.

  1. E3BK, Apr 24, 2017
    Last edited: Apr 25, 2017

    E3BK macrumors 68020

    E3BK

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    #1
    There are tons of articles like this and it always bothers me that these writers talk about lenses but never of crop factor. It makes a huge difference in the kinds of lenses they recommend! If you're going to write a few paragraphs about what the diff focal lengths are for, RIGHT AFTER you talk DSLR vs mirrorless, isn't it equally important do understand the crop factor of your camera body?

    Anyway, just a late night rant. Carry on. Lol
     
  2. kenoh macrumors demi-god

    kenoh

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    #2
    Yes and no. Yes crop factor does introduce a variable but I would hope that the way everything is kept to a standard scale i.e. 35mm full frame equivalent then it allows us to adjust our understanding easily. Once you know that your camera is APS-c you know any lens focal lengths need multiplied by 1.6 ish to get equivalent field of view, m43 is x2, FF is x1 and medium format is something like x0.5

    The thing is it is field of view that is the equivalent not perspective. It doesn't magnify the image any more by putting a 200mm on crop vs FF, just tightens the view.

    It's complicated but basically physics trumps lens design.

    Also the reviewers are likely always reviewing the lens on a camera the lens was designed for. Thus rendering crop factor as somewhat irrelevant to them.

    Why is it you have had to have a wee rant time out? What's up? Can we help?
     
  3. M. Gustave macrumors 68000

    M. Gustave

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    #3
    Perspective has nothing to do with focal length, it's solely a function of subject distance.
     
  4. kenoh, Apr 25, 2017
    Last edited: Apr 25, 2017

    kenoh macrumors demi-god

    kenoh

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    #4
    Don't want to argue with you but I disagree - not an expert though, optics not my area. T
    However if you take a 15mm, 35mm and 50mm at same subject distance they give completely different perspectives or the same scene.

    http://cameraontheroad.com/2005/10/lens-perspective/?cb=034268381861708597

    This one illustrates it well looking at the perspective of the building behind the girl. It is a function of focal length Vs distance. Distance being constant in a given scenario means the variable is focal length.

    http://www.disognophoto.com/portraits/shooting-for-a-class.html

    However the effect of perspective derived from the focal length of the lens doesn't change as a consequence of sensor size was my understanding.
     
  5. E3BK thread starter macrumors 68020

    E3BK

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    #5
    Haha. No, I'm fine. Just couldn't sleep last night and read that. I was in a mood.
     
  6. kenoh macrumors demi-god

    kenoh

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    #6
    Cool... just checking :)
     
  7. dwig, Apr 25, 2017
    Last edited: Apr 25, 2017

    dwig macrumors 6502

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    #7
    You may disagree, but you are totally wrong, both in that focal length has any direct influence on perspective and that the issue of perspective has any direct association with optics. Perspective is controlled solely by the relative distances from the viewer/camera to the foreground, subject, and background. Perspective was well described mathmatically centuries before the invention of photography.
    --- Post Merged, Apr 25, 2017 ---
    True, and this applies to many many topics discussed on the web. So many pundits are extremely sloppy/lazy in their wording.

    Anytime you discuss focal lengths you need to make sure that somewhere in the discussion it is made clear the camera format under discussion and that that information is repeated after any "break" in the thread that introduces any second format. If the thread continually discusses multiple formats then every mention of FL should include text to state the reference format.

    Personally, I rather like Michael Johnston's, editor of The Online Photographer, "mm-e" designation for "35mm full frame equivalent focal length in mm". It's short and easy to type. Too bad it hasn't caught on the way his coined term "bokeh" has (despite the large misunderstanding of the term in recent years).
     
  8. kenoh macrumors demi-god

    kenoh

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    #8
    Ok
    So I am wrong. So explain why when I stand 2m from my subject with tripod and camera, and the subject has an object behind them, that their relative height and position relative to each other changes when I use a 15mm Vs a 50mm. Is that not perspective?
     
  9. M. Gustave macrumors 68000

    M. Gustave

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    #9
    If you are taking both photos from the same distance, then they must have the same perspective and subject relationships. But the 50mm will obviously be "zoomed in" relative to the 15mm. That's field of view, not perspective.
     
  10. davybe macrumors newbie

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    #10
    I agree with M. Gustave (salut!). Field of view is how much you encompass around your subject, and perspective is the relative size of your subject against the background. They are different. Subject distance determines perspective, focal length determines field of view.

    I would add: here is where Perspective and Field of View do in fact relate: If you use a longer focal lenght but when to keep the same field of view you will need to step farther from your subject. Therefore, the perspective will change :)
     
  11. kenoh, Apr 25, 2017
    Last edited: Apr 25, 2017

    kenoh macrumors demi-god

    kenoh

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    #11
    Hmm no, still don't agree. Field of view usually represented in degrees is angle or arc visible in lens not magnfication represented as a multiplier. Let's not argue but maybe we are both interchanging terms and confusing each other.
    --- Post Merged, Apr 25, 2017 ---
    Ok in the interests of peace and harmony, you guys are right I am wrong...
     
  12. dwig, Apr 25, 2017
    Last edited: Apr 25, 2017

    dwig macrumors 6502

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    #12
    Quite true, and why I used "direct influence" in my post.

    Changing to a lens with a different field of view has an indirect influence on perspective when it causes the photographer to change position in such a way that the relative distances to subject compared to foreground and background change. This is why the common recommendations for, say, a portrait lens generally falls into a particular focal length range for a particular format. A lens of that FL, if used at a distance that yield typical "portrait" framing, will result in shooting from a distance that produces pleasing perspective.
     
  13. M. Gustave macrumors 68000

    M. Gustave

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    #13
    I'm not at all confused.

    Do you have a camera with a zoom lens? Go take two photos, at two different focal lengths, from the exact same distance from a subject. Now crop the wider shot to equal the field of view of the longer focal length shot. Report back here what the perspective of the two resulting photos is.
     
  14. kenoh, Apr 25, 2017
    Last edited: Apr 25, 2017

    kenoh macrumors demi-god

    kenoh

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    #14
    I already admitted I was wrong.
     
  15. davybe macrumors newbie

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    #15
    Hi kenoh,

    It does not matter who is right or wrong as long as the thread figure it out. However kudos to you for your exemplary (and rare) behavior on today's internet.
     
  16. kenoh macrumors demi-god

    kenoh

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    #16
    no problem, I considered deleting my incorrect information so someone doesnt follow in my "too long didnt read" error... but I am not a fan of deleting stuff that others can learn from.

    To add clarity to my foible... the bit I missed on my experiments was the "resize to the same size" bit which fixes the differences in the perspective as I understood it.

    Every day is a day to learn right?
     
  17. Mark0 macrumors regular

    Mark0

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    #17
    Speaking of learning - how did your weekend tutorial with Colin Prior go?
     
  18. kenoh macrumors demi-god

    kenoh

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    #18
    It was great. Still coming down off of it... Was not as intense as I expected, no heavy pitch from the camera sponsors and Colin is a nice guy. Got to ride shotgun in his car to go on location.

    Very approachable and very knowledgeable .
     
  19. Apple fanboy macrumors Core

    Apple fanboy

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    #19
    No heavy pitch? Given how much Leica gear you were carrying they probably figured they'd milked you dry!

    Did you see an M10?
     
  20. kenoh macrumors demi-god

    kenoh

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    #20
    I got to play with a M10 extensively, a Titanium Q and an SL with the 24-90mm wine bottle on the front..

    Honest thoughts?

    Q is lovely, fabulous to have round your neck but as it is 28mm, as suspected it is too wide for me as I have to get too close to isolate and I am more and more thinking I am an isolated subject rather than wide shooter so nope not for me.

    M10 fabulous but errr... EXACTLY the same as the M9. Some tweaks like the viewfinder magnification and the way way way better screen, and live view. Feels thinner, shutter sound is way way better but meh, I love my 9 and I mean I ADORE my 9... the way I came about it and bond I have with it as a consequence means I am not in a rush to replace it.

    SL is like a Sony A7Rii in a tuxedo... EVF is beautiful and images are lovely but net net, no tangible wow factor over and above the A7Rii and the lenses are monumentally huge! the 50mm summilux for it is comically big, I mean "you are kidding right?" so I ended up using my Sony for most of my shoots.

    Note these comments are purely my own opinion, anecdotally, YMMV, no science i.e. a SL is obviously NOT a dressed up sony... but I now know that actually, I would be better getting the 24-70 GMaster for the A7Rii than switching to a SL system.

    Now this MAY just be because of my pathetic skills with a camera. Either way, for where I am right now, the Sony by far exceeds my capabilities so anything more/else would be a waste and as the only thing that I dont adore about the M9 is the shutter sound and screen so I am not going to drop £5,800 on an M10 anytime soon - this one might bite me in the butt later...

    What I did see was a Gitzo tripod in use and ah... I now know what a sturdy tripod feels like.... DAMNIT!!!
     
  21. Apple fanboy macrumors Core

    Apple fanboy

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    #21
    My Gitzo is beautiful. Just hope I get some use out of it one day! Still not getting out very much due to Home stuff. I was looking at my photos this year and I'd taken more of Mrs AFB cards than anything else!

    Glad your happy with what you've got body wise. Latest and greatest doesn't always produce a better image.
     
  22. kenoh macrumors demi-god

    kenoh

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    #22
    Happy with my cameea bodies.... my body body different story.

    Yes the Gitzo is lovely. Very nicely made and yeah easy to carry...
     
  23. Apple fanboy macrumors Core

    Apple fanboy

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    #23
    I actually like the thought that went into the design. I can appreciate it as an (ex) engineer.
     
  24. Mark0, May 3, 2017
    Last edited: May 3, 2017

    Mark0 macrumors regular

    Mark0

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    #24
    Which one did you go for?
    --- Post Merged, May 3, 2017 ---
    Sounds like a great experience. If I had the money going spare I'd like to do a location based shoot with him. He is a great orator and undoubtedly a very intelligent guy. He was a major influence in me getting serious about photography in my early teens.

    Another guy I'd like to do a tutorial with is Bruce Percy. I'd love to see how he goes about 'seeing' the landscape. I'm working with simplicity a lot at the moment and it's actually quite difficult to get the 'less is more' just right. Bruce Percy is a master of simplicity through strong visuals. He is also a very intelligent guy and his blog is certainly worth reading.
     
  25. kenoh macrumors demi-god

    kenoh

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    #25
    Wow! Bruce Percy's work is fantastic!

    I am looking to do some more sessions with Colin P. Maybe we can make the economics work between us... will let you know when I work out what I am looking for.
     

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