Do I have to sacrifice sharpness for large aperture?

Discussion in 'Photography Beginners' Forum' started by Langdon_Alger, Aug 10, 2010.

  1. Langdon_Alger

    Langdon_Alger TPF Noob!

    Joined:
    Aug 6, 2010
    Messages:
    2
    Likes Received:
    0
    Can others edit my Photos:
    Photos OK to edit
    I bought a Canon EF 50mm f1.4 USM for my Canon T1i to take indoor pictures without a flash. The problem is, I can’t seem to get good results wide open at 1.4.

    I understand that large aperture means very narrow DOF, but even using a tripod and remote shutter release there is not a single part of the picture that is sharp when I zoom in during PP. I’ve tried manual and auto focus, mirror lockup, with and without UV filter. The same lens at roughly f2 or higher is vastly sharper.

    Is this just a known tradeoff for large aperture lenses? For this specific lens? Was this particular lens from a bad batch? Should I do anything different (different filters, or keep the subject further away?).

    Thank you kindly for any help…
     
  2. shaunly

    shaunly TPF Noob!

    Joined:
    Mar 20, 2009
    Messages:
    575
    Likes Received:
    6
    Location:
    Orange County, CA
    Can others edit my Photos:
    Photos NOT OK to edit
    Where is your ISO at? High iso will decrease sharpness.
     
  3. clanthar

    clanthar TPF Noob!

    Joined:
    Aug 2, 2010
    Messages:
    767
    Likes Received:
    86
    Location:
    Saint Louis MO
    Can others edit my Photos:
    Photos OK to edit
    Hi,

    A lens's performance is variable over it's aperture range. The difference can be as much as a 30% loss at either end. A lens generally performs at it's best two or three stops down from wide open.

    This is a long standing dilemma -- you bought the fast lens to get that extra f/stop or two but.... It's always a compromise.

    Joe
     
  4. tirediron

    tirediron Watch the Birdy! Staff Member Supporting Member

    Joined:
    Jul 8, 2005
    Messages:
    37,416
    Likes Received:
    10,678
    Location:
    Victoria, BC
    Can others edit my Photos:
    Photos OK to edit
    Lenses in general are never at their best wide open. One stop down will normally make a significant difference, but the 50mm 1.4 is rumoured to be a pretty decent lens. As mentioned ISO, and exposure can have a significan impact on how sharp an image is; examples would help.

    In the meantime, I suggest a home-made lens resolution test: Use a LASER printer (NOT inkjet) to completely cover a sheet of paper with 12pt upper-case 'X's. Using a tripod, level and square, position your camera such that it is within the minimum focusing distance (eg, if your lens will focus as close as 12" then use, say, 14") and ensure that the sheet of paper is exactly square to the lens axis. Use your lowest native ISO, and supplementary lighting if necessary to ensure a correct exposure.

    Focus on the centre on the of sheet of paper and make an exposure wide open, followed by a series stopping down by a couple of stops each time. Then, examine the centre, and edges at 100% and compare sharpness. Even wide open, at the edges, the characters should be legible. This will give you a good idea of whether or not there is a problem with the lens (It's unlikely, but it can happen) and just how it performs at different apertures.
     
  5. Einstein

    Einstein TPF Noob!

    Joined:
    Jan 3, 2010
    Messages:
    228
    Likes Received:
    2
    Location:
    Bermuda
    Can others edit my Photos:
    Photos OK to edit
    I have the same lens and find it takes increadible photos. However at f 1.4 the DOF is SO narrow it is hard to get anything larger than a few millimiters of the subject in proper focus. I find shooting above F2 helps.

    Also if your shooting portraits indoors its best to go with a flash and use a narrower apperture so you can get more of your subject in focus.
     
  6. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

    Joined:
    Dec 16, 2003
    Messages:
    33,822
    Likes Received:
    1,811
    Location:
    Edmonton
    Can others edit my Photos:
    Photos NOT OK to edit
    Yes, I think the first thing to investigate is whether or not you are actually getting accurate focus. At F1.4, especially at close distances, the DOF can be very, very thin.

    Along with Tirediron's sharpness test, you might also try shooting a test sheet at 45 degrees to camera, so that the focus will come and go withing the frame. Find the sharpest part of the image and that should give you an idea of what sharpness the lens is capable of. This test can also help to tell you if your lens & camera are focusing accurately. It's entirely possible that either your lens or camera is not calibrated 100% accurately and thus doesn't focus exactly where you think it will.
     
  7. Christie Photo

    Christie Photo No longer a newbie, moving up!

    Joined:
    Jan 7, 2005
    Messages:
    7,006
    Likes Received:
    67
    Location:
    Kankakee, IL
    I often times hear DOF referred to as "narrow."

    A better way to think about this is either "shallow" or "deep." This may help in your understanding of what's going on.

    -Pete
     
  8. Langdon_Alger

    Langdon_Alger TPF Noob!

    Joined:
    Aug 6, 2010
    Messages:
    2
    Likes Received:
    0
    Can others edit my Photos:
    Photos OK to edit
    thanks for all the replies.... I did some more test shots, and I guess I would really have to call it more of a "haze" than a lack of sharpness...

    I tested it using ISO 100, of a grassy slope in the sunlight (so if it was a DOF issue, there should always be at least one point along the slope thats in focus).

    I went and read some reviews of this lens, and its rated very good overall, but the ones that rated it low usually complained of the "softness" at large aperture. Now I regret paying extra specifically to get a low f number that I can't use! Luckily this lens seems to have a good resale value, it will be going on ebay soon...:x
     
  9. Petraio Prime

    Petraio Prime TPF Noob!

    Joined:
    May 28, 2010
    Messages:
    1,217
    Likes Received:
    0
    Location:
    Ohio
    Can others edit my Photos:
    Photos NOT OK to edit
    Generally speaking, with some exceptions (such as some Leica APO lenses) wide-open performance on lenses is worse than stopped down a couple stops. This is true more with high-speed lenses than with ones of moderate aperture. So, your 400mm f/5.6 lens may not be any worse at f/5.6 than it is at f/11, but your 50mm f/1.4 will often be noticeably better at f/4 or f/5.6.

    There are, of course, exceptions. They are very expensive ones, needless to say.

    Leica 50mm F0.95 Noctilux-M ASPH Lens 11602
     
  10. KmH

    KmH Helping photographers learn to fish Supporting Member

    Joined:
    Apr 9, 2009
    Messages:
    38,255
    Likes Received:
    5,010
    Location:
    Iowa
    Can others edit my Photos:
    Photos OK to edit
    So what do you replace it with? A less expensive, lower quality lens that gives less sharpness overall, not just wide open?

    You didn't mention what file format you are using, nor did you mention what sharpening techniques you are using.

    Do you do any capture sharpening? What about local sharpening? How are the photo's used? Online only? Print?

    What are the photo's of?

    How a photo will be used, and the content of the photo, has a lot to do with how it should be sharpened.
     
  11. Hardrock

    Hardrock TPF Noob!

    Joined:
    Apr 8, 2009
    Messages:
    1,173
    Likes Received:
    36
    Location:
    Dallas
    Can others edit my Photos:
    Photos NOT OK to edit
    http://www.thephotoforum.com/forum/people-photography/200059-my-favorite-model.html
    I believe #1(the shot with her sitting in the blue bonnets) is shot wide open or very close to it and I think it came out pretty well. Im at work and cant see the exif or the images. The 50mm F1.4 should work pretty well even at F1.4 and it gives a dreamy look. I think the lens works the best at F2.2 and above. Its a great lens once you figure it out. I made a post when I first got the lens and thought something was wrong with the lens but it was me. At a shallow DOF you really cant focus and recompose. Good luck!
     
  12. Einstein

    Einstein TPF Noob!

    Joined:
    Jan 3, 2010
    Messages:
    228
    Likes Received:
    2
    Location:
    Bermuda
    Can others edit my Photos:
    Photos OK to edit
    [​IMG]

    Example shot straight out of camera, i think this was under f2 but i cant remember. Awesome lens IMO, maybe you got a lemon?
     

Share This Page

Search tags for this page
50mm f0.7 sold at christie
,
examples of large aperture
,
focusing problems with large aperture
,
how to get sharp image at large aperture
,
large aperture image not sharp
,

large aperture sharpness

,
sharpest wide aperture lenses
,
why is wide aperture not sharp
,
why large aperture not sharp
,

wide aperture sharpness