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New to the NEX-6, depth of field questions

Discussion in 'Sony Alpha E-Mount Cameras' started by kyngfish, May 2, 2014.

  1. kyngfish

    kyngfish New to TalkEmount

    5
    May 2, 2014
    Hi,

    I'm new to the forum and the NEX 6. Aside from a photography class in college, I don't know much except for my feverish reading the last few weeks. I have a questions and I hope this is the right forum. I have an NEX 6 that came with the 16 - 50mm e-mount lens. I've always liked pictures with a shallow depth of field, reason being, is I believe for near to mid-distance photography, that's how the human eye sees images. I've been experimenting with this camera in manual mode and am having trouble creating a shallow depth of field, and I'm trying to assess if I'm doing something wrong or I am using the wrong lens. In the pictures below, the first has what I believe to be a pleasing depth of field, only the front of the garment is truly focused, it is shot up close in full auto mode using autofocus. f5.6, 1/30, ISO3200.

    The second picture was in full manual mode and manual focus (my apartment is a mess), f3.5, 1/30(?) and ISO800. My goal was to focus on the small brown box in the middle of the image which I did manually, and hopefully blurring out everything in between. Obviously I failed. I notice that this lens only goes down to f3.5 and many of the things I was reading were suggesting a wider aperture for a shallow depth of field, yet it seems to have achieved more like the effect I want in the first photo. Can someone give me some pointers?

    Cheers!
    Martin
     

    Attached Files:

  2. Mathieu Decodts

    Mathieu Decodts TalkEmount Veteran

    282
    Aug 5, 2013
    Welcome to the forum, its awesome! Photographers and amateurs, eveyone here is lovely.
    regardless of what you want, this is the right place :)
    so F stop: this was shot at f3.5

    11350429054_e486b329a7_b. Canon FD 135mm and Speedbooster by Mathieu Decodts, on Flickr

    In short the f stop is only part of the depth of field equation. (a £25 old manual lens too :) )

    the problem with your second pic is your relative distance to the item you want in focus and the items you dont want in focus.

    !!Warning!! boring science bit (research "hyperfocal distance")

    In short make the thing you want in focus relatively closer to the lens than the thing you want out of focus. the F stop does effect this, but your relative position and focal lenght has a much greater effect.

    That cat shot was at the minimum focus distance (1 metre) with a 135mm lense at f3.5 the chair was about 3 metres away. (3:1 ratio)

    So relatively it was 3 times further away. If I shot the cat from 3 metres away the ration would be 1:1 and the chair would be much sharper relatively speaking.

    its REALLY hard to understand this in words so just teach yourself. :p

    Set your camera aperture, iso and shutter manually and dont change anything at all except your position and the kit zoom. walk back and zoom in and take a picture. then walk forward and zoom out trying to take the same picture as you go. you will notice a massive change in depth of field as you go.

    With your lens to get the smallest depth of field zoom in to 50mm and get as close to the box as you can (minimum focus should be about 1metre or less)

    have a mess and report back here :p
     
  3. WestOkid

    WestOkid TalkEmount All-Pro

    Jan 25, 2014
    New Jersey, USA
    Gary
    Depth of field is as much a product of focal length and focus distance as it is aperture. The first picture has shallower DOF becuase you're much closer to what are focusing on. @ f/3.5 with that focal length and distance will not allow you to blur out the stuff in front and behind the box.
    See the attached DOF calculator for what you would need to accomplish your goal.

    http://www.cambridgeincolour.com/tutorials/dof-calculator.htm

    Sent from my XT1053 using Tapatalk
     
  4. WestOkid

    WestOkid TalkEmount All-Pro

    Jan 25, 2014
    New Jersey, USA
    Gary
    Didn't see Mathieu's answer when I posted mine. He is much more qualified to answer, however you should run some examples using the DOF calculator in the link I provided. It helped me understand. In fact I actually downloaded an app for my smartphone.
     
  5. Bimjo

    Bimjo Super Moderator

    Oct 28, 2011
    Washington State
    Jim
    Hi Martin, welcome to the forum. :)

    Depth of Field (DOF) is made up from several factors- size of recording media (film or sensor), focal length of the lens, aperture of the lens, and distance to the subject. I like to use this online DOF calculator, which is also available as an app for your smart phone.

    Making some assumptions (generally a bad idea, but we'll run with it ;) ) about your second shot we'll assume that you shot it at 16mm f/3.5 from about 6 feet or so. The calculator tells us that everything from 4 feet from the camera to 12 (just over 8 feet total) feet from the camera is in focus, which is pretty much what you see.

    If you change the parameters in the calculator to 50mm f/3.5 (not possible with your lens, but for illustrative purposes we'll do it anyway) you end up with everything between 5.7 and 6.3 feet (total DOF .61 feet) from the camera in focus.

    If you carry the execise another step and assume you could shoot this at 100mm f/3.5 you'd get a DOF of 0.15 feet. That's 1.8 in/45.7mm.

    So, you can see that changing nothing but the focal length of the lens can drastically change the DOF for a given scenario. Moving the camera or changing the aperture also have a effect on DOF.

    The calculator isn't perfect, but it's close enough to show that as you plug numbers into the calculator you can start to get an idea of how these things are related to one another and how to reach your goals.

    HTH
     
  6. Bimjo

    Bimjo Super Moderator

    Oct 28, 2011
    Washington State
    Jim
    Hehe, I need to learn to type faster. Good job guys! :)
     
  7. davect01

    davect01 Super Moderator

    Aug 20, 2011
    Fountain Hills, AZ
    Dave
    Welcome and good advice so far.

    Only thing I would add is what you already hinted at. The 16-50mm does not stop down very far and so you will not get as deep of a DOF effect as you will with other lenses.
     
  8. kyngfish

    kyngfish New to TalkEmount

    5
    May 2, 2014
    Amazing, thank you guys for the feedback, this is excellent information. Lets see if I understand this correctly, the closer I am to the object I am focusing on, the shallower my depth of field will be relative to the f-stop setting. The F-stop setting also affects the depth of field, the lower the more shallow my DOF surrounding the item I am focused on. The greater my zoom is, optically, is the third item which affects the DOF, so my f3.5, if it were possible at 100mm would be much shallower than at 50 or 16mm. So if for example, I am shooting something with three major objects at relatively near intervals, say in my second shot, the chair at 3 feet, the table at 6 feet and the other table at 12 feet, I would need a much lower F-Stop setting than what is actually available in my lens to show a stark focus difference between the three because at my available f-setting, 3.5, my depth of field is actually fairly deep.

    What you say above really is what I feared, that my lens isn't really the right tool for those kinds of shots. If I am understanding correctly, what kind of lens should I be looking at? I've seen the 55-210mm, but the F-setting on that isn't especially low either. My goal is to be able to shoot shallow DOF shots at a medium range, i.e., not really closeups, but objects say between 3 - 20 feet.

    Thanks again for the advice! Great forum.
    Martin
     
  9. eno789

    eno789 TalkEmount Top Veteran

    720
    Jan 1, 2012
    NoCal, USA
    Brian
    Everything else being equal,

    1) The closer you focus to, the shallower the DoF (that's also why macro is more difficult to focus);
    2) The longer the focal length, the shallower the DoF;
    3) The wider you open up the aperture (smaller the aperture #), the shallower the DoF;
    4) The bigger the sensor, thus smaller the crop factor, the shallower the DoF.

    I'd suggest to get a cheap adapted lens with max aperture <= f/2. You can see the difference immediately.
     
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  10. kyngfish

    kyngfish New to TalkEmount

    5
    May 2, 2014
    I have a 28mm lens on my Grandfather's EOS 1n film camera. It says 1:2.8, I'm assuming that's the highest aperture. A Canon 50mm II with 1:1.8. Will those do the trick? Only on the second one I can't see a manual setting for aperture, and I'm not sure an adapter will let my camera control that. I'm seeing a wide variety in price for adapters. Can you point me in the right direction?
     
  11. eno789

    eno789 TalkEmount Top Veteran

    720
    Jan 1, 2012
    NoCal, USA
    Brian
    Canon changed their mount from FD to EOS when they switched to auto-focus. The EF mount uses electronic connection between lens and body to control the aperture. That's why there's no aperture ring. There might be Canon EF to Sony E adapter out there, but I've no personal experience with these.

    It's much easier to adapt older manual focus lenses, both for the aperture ring, and great tactile feel of the manual focus ring.

    Look keh.com 35mm film camera lenses, Konica/Minolta MF are all good choices.

    Once you decide on the lens, look for the matching adapter. My experience is cheap adapters are good enough. I often get them at http://rainbowimaging.biz/ as they have stock in US, you don't need to wait very long.

    For learning, open up the aperture as much as you'd like. But for shooting, even I want to emphasize the shallow DoF, I almost always shoot stop down a bit (unless the lens is proven to be good wide open).
     
  12. davect01

    davect01 Super Moderator

    Aug 20, 2011
    Fountain Hills, AZ
    Dave
    Good advice.

    I currently have two MF lenses and two AF lenses. There are times when it is nice just to AF and let the camera handle the proccessing, then there are times when it is nice to go Manual.