Lens sharpness, how do you tell?

Discussion in 'This or That?' started by yakky, Mar 2, 2014.

  1. yakky

    yakky Mu-43 Top Veteran

    Jul 1, 2013
    I'd like to honestly be able to say one lens is sharper than another, between different systems, but I think this is pretty difficult, even when using raw. It seems pretty easy on a single body, I can switch between a kit lens and something a bit better like a moderately priced prime, say the Sigma 30. The difference is pretty apparent.

    However going between two systems, how do you guys do it? Say comparing a M43 lens to something on a DSLR. How do you factor out sharpening introduced by the camera and/or AA filter differences? Then compound the problem by sharpening in PP, I can make the cheaper lenses look nearly as good, true I have to use more sharpening for the same effect.
  2. Luckypenguin

    Luckypenguin .

    Oct 9, 2010
    Brisbane, Australia
    Real Name:
    The only fair way that I can compare camera and lens combinations from within systems or between systems is based on their post-processed output. How it gets there is less important to me than where it gets to.
    • Like Like x 1
  3. Dogman

    Dogman Mu-43 Regular

    Dec 23, 2012
  4. pellicle

    pellicle Mu-43 All-Pro

    Feb 10, 2010
    Southport, OzTrailEYa
    Real Name:
    I photograph something I know and compare it to the other photographs. If I think they have as much detail as I need then they're sharp enough.

    Naturally when making such comparisons on needs to remove personal errors (focus mistakes, camera shake, subject movement) from the equation. So I tend to used tripod and probably flash too.

    I also tend to photograph both low contrast subjects (white wall paper with a white texture) and high contrast subjects to see both the low frequency MTF and the higher frequency MTF bits.
    If you can't tell the difference then they're within ball park :)

    Some (possible) food for thought in this comparison of two different lenses on the same body ... but equally you can compare images made with different bodies and the same lens if you chose to (just keep field of view equal).

  5. bikerhiker

    bikerhiker Mu-43 All-Pro

    Dec 24, 2013
    Real Name:
    It depends on the output device, be it a monitor screen or a print and your vision which is considered a lens optics system with its own MTF rating to discern final sharpness. Some professional lens review services provides both an SQF (Subjective Quality Factor) rating based on final printing viewed at a certain distance and an MTF reading based on lines. Say, there is a minimum standard of how many lines it can faithful reproduce from a chart to be called sharp. That's base line sharp. So for instance, take a kit lens 14-42 Mark I @ 14mm with an MTF reading of 2300 lines and the base line is 2100 (taking consideration of human vision minimum limits), then the lens is considered sharp at that focal length. Bring a prime or a pro zoom @ the same focal length and it resolves 2500 lines, then it's considered sharper than the kit lens. Today's monitors can display high PPI, so you can see a difference in between. But most people don't have high end monitors, like the Retina display on macs or equivalent, so if you had taken a photo with a prime and a kit lens, a person who has a low end monitor may not see a distinct difference until you pixel peep. Or for a print of a certain size even.
  6. mcasan

    mcasan Mu-43 All-Pro

    Feb 26, 2014
  7. nickthetasmaniac

    nickthetasmaniac Mu-43 All-Pro

    Jan 11, 2011
    I don't factor in or out anything. I judge the image as I see it and go from there. Given that how I see it is all that really matters in the end, I don't much care how technically accurate my judgement is :smile: