Bokeh doubt (50mm vs 24mm)

Discussion in 'Photography Beginners' Forum' started by Meredoth, Nov 26, 2017.

  1. Meredoth

    Meredoth TPF Noob!

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    Hello all!

    Let's say I have both 50mm and 24mm, the STM ones from Canon. If I record a video (same settings, light, etc.) with those lenses, both at f/4, will the bokeh be different?

    I know the bokeh of 50mm is better but is it better only at 1.8, since the 24mm is just 2.8?

    I also read here and there that the 1.8 of the STM lens is not that good. What are your guys opinion? I already have the 24mm, wondering if I should get the 50mm. My main goal is video, and though it's indoors, I have the space for the 50mm.

    Thanks!


     
  2. 480sparky

    480sparky Chief Free Electron Relocator Supporting Member

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    Every lens renders bokeh differently.
     
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  3. photo1x1.com

    photo1x1.com TPF Supporters Supporting Member

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    A lens with a longer focal length will always have shallower depth of field. So at f4 - both will definitely have a very different amount of blur (the 50mm having much more). You sure have a zoom lens (maybe a kit lens that came with your camera body). Try that at the same f-stop at 24mm and 50mm, and see for yourself.
    The much more apparent difference will be the distortion and angle of view though. A 24mm lens renders images very differently than a 50mm lens does.

    Regarding bokeh: if you take several different 50mm lenses, they all will roughly render the same amount of background blur at the same f-stop. But the "quality" of the blur will be different. Some are smoother, but others will show the shape of the aperture opening (if it is not completely round).
     
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  4. Meredoth

    Meredoth TPF Noob!

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    I see. That's some good news, and I guess it makes the purchase of the 50mm STM worth it, even though I already have the 24mm.

    And I actually do not have the kit lens, I got the camera body only and used the money to get my 24mm. :D
     
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  5. photo1x1.com

    photo1x1.com TPF Supporters Supporting Member

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    Which type of camera do you have full format, or crop? I can make a testimage for you if you like.
     
  6. Meredoth

    Meredoth TPF Noob!

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    Oh, that would be nice! I have a SL2, cropped.
     
  7. photo1x1.com

    photo1x1.com TPF Supporters Supporting Member

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    OK, here we go. There is nothing fancy going on here at the moment, so the images are not spectacular ;).
    To explain: my old 400D battery was dead, so I had to use a full frame body and cropped the middle - that would render exactly the same image than shooting from a crop format sensor. The lenses I used were Sigma 50mm F1,4 EX DG HSM (at f1.8!!!) and Canon 24mm f1.4 LII (at f2.8!!!) to give you the depth of field of the lenses you are considering or owning. As said above - the bokeh is something different, we are only talking about depth of field and background blur.

    Image Nr. 1: 50mm @f1.8 (click to enlarge)
    50mmf1-8Crop.jpg
    Image Nr. 2: 24mm @f2.8
    24mmf2-8Crop.jpg
    Both of the above images were shot from a tripod, same position - only the lens was changed.
    To give you an even better idea, I also took a shot with the 24mm and moved closer to the subject so that the crop of the main subject is roughly the same.
    Image Nr. 3: 24mm @f2.8 from a closer distance
    24mmf2-8CropCloser.jpg

    I hope that helps you with you with your decision. Keep in mind that things change when you move your subject or the background:
    • the closer your subject is to the camera the more blurred your background
    • the further away your background from your subject, the more blurred the background
    And here are the other factors that blur the background:
    • a wider aperture (lower number): more blur
    • a larger sensor (because you move closer to frame the subject): more blur
    • a longer focal length: more blur
     
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  8. Meredoth

    Meredoth TPF Noob!

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    Hey, many thanks for the post!!! Really helpful! And the shots are really cool! :D

    One thing that I'm doubt is that comparing pictures 1 and 3, even though the subject is "framed" (not sure if it's the right term) the same way, the background is different. On the first picture it's possible to see only the top of door and windows, while in picture 3 it's possible to see much more like the balcony.

    Was my understanding that getting close to the subject (with a different lens) would eventually give the same... content on the picture. Guess I was wrong? hehe
     
  9. JonA_CT

    JonA_CT TPF Supporters Supporting Member

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    The autofocus on the Canon 50mm f1.8 is stupid loud, if that helps your decision at all. I'd call it almost unusable if you are using the on-board microphone.
     
  10. photo1x1.com

    photo1x1.com TPF Supporters Supporting Member

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    Hahaha, If there is one thing that I doubt then it is, that the shots are cool :D.
    Every focal length has a different field of view. So getting closer to framing the foreground in image 3 didnĀ“t have much influence on the background.
    To understand that, get outdoors, and look through an empty roll of toilet paper to narrow your field of view.
    Now walk towards a car that is rather near. You will see that you will soon only see parts of the car.
    But you will also see that while the small walking distance had such a big influence on the close object, it only has minimal influence on things that are far away.
    If you walked 5m towards the car, you might now only see the keyhole. But if you had a wide open field and walked the same 5m, you would still have almost the same view through your toilet paper roll.

    Stupid example, but does that make sense for you?
     
  11. Braineack

    Braineack Been spending a lot of time on here!

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    this is exactly what I'd expect to see when shooting 50mm vs. 24mm...
     
    Last edited: Nov 27, 2017
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  12. KmH

    KmH Helping photographers learn to fish Supporting Member

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    Don't make the very common mistake thinking that bokeh and depth-of-field are the same thing, because they aren't.
    Bokeh cannot be adjusted and is an inherent property of each make/model of lens.
    Depth-of-field is adjustable and is controlled mainly by point of focus distance though lens aperture, image sensor size, and lens focal length factor in.
     
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