Low Fstops & Crisp Photos

Discussion in 'Beyond the Basics' started by Jade16, Nov 4, 2015.

  1. Jade16

    Jade16 TPF Noob!

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    I keep trying to get crisp photos with very low fstops. I stand farther back, but eyes are still not crisp at 2.8, 3.2, etc. what the deal? Help? Tips? any tricks? what am I missing? and yes my shutter speed is 200 or above and ISO is decent.


     
  2. 480sparky

    480sparky Chief Free Electron Relocator Supporting Member

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    How are you focusing? What lens are you using?

    You still need to go to f/4 or 5.6
     
  3. KmH

    KmH In memoriam Supporting Member

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    Understanding Depth of Field in Photography

    IIRC you use a Canon 5D MK III camera.

    The 5D MK III image sensor has an Anti-Aliasing (AA) filter in front of it.
    The AA filter helps control moiré but it also cause photos to lose some sharpness.

    Consequently, photos made with a 5D MK II will need to be sharpened to some extent. Photos destined for electronic display generally cannot be sharpened as much as photos destined for printing.
    Image sharpening using Adobe Ps, LR, ACR is a book length subject:
    Real World Image Sharpening with Adobe Photoshop, Camera Raw, and Lightroom (2nd Edition)

    Most fast (f/1.2, 1.4, 1.8, 2, 2.8, 3.5) lenses need to be stopped down 1 to 2 stops before they start to deliver their sharpest focus.
    f/2.8 is a bigger number, and a bigger more open lens aperture, than f/3.5 is.
    Understanding Camera Lenses
    Tutorials – Sharpness
    Understanding Camera Autofocus
     
    Last edited: Nov 4, 2015
  4. Vtec44

    Vtec44 Been spending a lot of time on here!

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    Post some samples. I shoot at between f1.6 to f2 all the time :)
     
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  5. EIngerson

    EIngerson Been spending a lot of time on here!

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    Lots of things come to mind with this.

    Too close to subject
    Front/back focus
    Not having your lens micro adjusted to your camera.

    Just to name a few. Like others said, post an example. Then we can see what the issue is.
     
  6. SoulfulRecover

    SoulfulRecover Been spending a lot of time on here!

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    Don't Canons have the 100% crop focus button (for a lack of a better name) to check your focus?

    I tend to have issues like you're describing.
     
  7. astroNikon

    astroNikon 'ya all Bananas I tell 'ya Supporting Member

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    post examples as mentioned.
    And your "stand farther back" ... isn't very descriptive. such as you were at 1 foot, now 200 feet ?? or 1 foot now 2 feet? 5 now 10 ?

    If you use a Depth of Field calculator ==> A Flexible Depth of Field Calculator
    you can determine, what many people have a problem with, is the actual depth of field based on your focus point (Do you understand the various Focus Modes and just don't allow the camera to select a focus point on it's own ?) ; in relation to aperture and distance from the subject.
     
  8. Jim Walczak

    Jim Walczak No longer a newbie, moving up!

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    I have to agree with Vteo that a few pics might help diagnose the problem...and more info about what gear you're using might help too. In lieu of that, there are a few things that could cause such a problem.

    When you're using low f/stops, you are generally dealing with a very shallow DOF (Depth Of Field). Depending on your lens, your distance to the subject, etc., it may take just a slight miss with your focus point to throw something like the eyes out of focus. Likewise, how you use the focus point in your camera can have a HUGE impact on this as well...many novices for example don't know they can use a single focus point and will have ALL of them turned on. Also remember that your shutter speed should be equal to or better than your focal length. You said you're shooting at f/2.8 at 1/200 second, but you haven't provided the focal length...if your shooting at 200mm for example, that 1/200 of a sec could be too slow.

    On the issue of DOF alone, my advice would be to look closely at the picture...ALL of the picture...and see if that sharp point of focus is perhaps landing somewhere else. This alone should tell you if it's actually your aim or something else.

    Also, while this is a bit more subjective, I've found that sometimes the aim of the focus points aren't quite as accurate as you might expect. Both of my Canons for example used to shoot just a little low of the center focus point in the view finder. I do a lot of critter photography, particularly dogs, and with my Canons I used to have to aim the camera just a bit high...if I tried to lock the center focus point onto the eyes, the camera would usually focus on the nose instead, so I had to aim the camera a little high (say, the dog's forehead), lock the focus, then re-compose the shot a hair (or allow a bit of room for a crop).

    There are of course a number of other things that can contribute to such problems as well...dirty lens, dirty sensor, low quality filters, yadda, yadda. A lot of novices for example will buy a DSLR and get conned by a salesperson into buying a UV filter "to protect the lens"...cheap filters will ALWAYS degrade your images to one degree or another. I had also once gotten a used Tamron lens for dirt cheap because the seller claimed it "was really soft on the focus"...turns out someone smeared some Vaseline or something on the lens (an old portrait photographer's trick) . Once I cleaned the goo off, the lens was just fine. Then of course there's your subjects...some people just can't hold still for more than a split second, making it difficult to keep the eyes perfectly focused if the lens is wide open. Children for example (like critters), can often be REALLY hard to shoot with a super shallow depth of field, just because they always seem to be moving! LOL! There's a very good reason most portrait photographers shoot around f/8...aside from usually being the "sweet spot" of the lens, it gives you a bit more room to work with should someone flinch.



    So again, without seeing some pics and having more info, it's hard to give any specific advice here, however, while these are just my own opinions, I hope it gives you something to work with.
     
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  9. ridnovir

    ridnovir TPF Noob!

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    Carefully read the post by Jim above and if still wish for better sharpness wide open I suggest Zeiss Otus lenses
     
  10. KmH

    KmH In memoriam Supporting Member

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    FWIW - F/2.8 is a bigger number, and a bigger lens opening (aperture), than f/4 is, because they are fractions.
    The f is equal to the focal length of the lens you are using, or that the lens is zoomed to if it's a zoom lens.

    Set to f/2 a 100 mm lens has a lens opening that is 50 mm wide - 100mm (f) / 2 = 50 mm
    Set to F/4 the same 100 mm lens has a lens opening that is 25 mm wide - 100 mm (f) /4 = 25 mm.

    How shallow depth-of-field is depends on several factors;
    1. Image sensor size
    2. lens aperture
    3. lens focal length
    4. point of focus distance

    Understanding Depth of Field in Photography

    Many 'fast' prime lenses (say - f/1.4 to f/2.8) need to be 'stopped down' before they start to deliver their sharpest focus.
    Consumer grade fast prime lenses often need to be stopped down at least 2 full stops before they deliver their sharpest focus.
     
  11. jake337

    jake337 Been spending a lot of time on here!

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    What's your sharpness post processing work flow? There is sharpness and then there's apparent sharpness.
     
  12. D-B-J

    D-B-J Been spending a lot of time on here!

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    Post examples. I've shot between f1.4 and f2 all day and had no sharpness issues.


    Sent from my iPhone using Tapatalk
     

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