Lens Sharpness

B

blahblah

Member
In reading all of these photographic reviews of lenses, it's clear that sharpness is everything. That makes sense when you're talking about resolving 21.1 million pixels (5Dmii). With respect to video, I've read that the resolution is only 2 million pixels. Am I correct then in reading these reviews with a grain of salt? I mean if a lens is soft at F1.4 on a 21.1 MP still, is it really going to be an issue at 2MP?

I see this as working to the advantage of the VDSLR filmmaker.
 
indeed res is not relevant

chrom aberation and barrel distortion are still visible and harder to correct however

S
 
I'd argue that sharpness is one of the most critical characteristics of a lens, but it isn't "everything." (Your assertion of sharpness of lens being separate from the resolution of the sensor, and/or how much/little of that sensor is used to render HD video, is correct.)

Watching a movie like "The Diving Bell and the Butterfly," reading posts here about anamorphic lens adapters and non-obvious lens choices, or visiting lomography.com shows that there are many more characteristics that need to be evaluated when buying a lens.

- Sharpness
- Chromatic Aberration (exhibited most often as purple fringing around high-contrast edges)
- Barrel Distortion (classic issue on wide angle lenses, expensive to correct)
- How the lens deals with flare
- Bokeh (shape of out-of-focus highlights, based on # of blades in the iris and their curvature)
- Focus ring behavior (continuous, as in Canon lenses, vs. hard stop, as in Zeiss lenses)
- Smoothness of focus and zoom ring rotation/action
- Weight
- Number of lens elements

This isn't a complete list, but it's what I base my own lens buying decisions on. It's led me to buy $1600 lenses and $50 lenses, and helped me to love each end of the spectrum for their respective strengths, even if it's hard to describe the "feel" of a given lens in technical terms.
 
Sharpness is often not that important for most lenses. Most lenses are "sharper than a digital camera's ability to resolve fine detail" (to quote Ken Rockwell) at 12-25 MP, let alone at 2 MP for video as the poster mentioned.

Unless your lens is broken or defective, it should be plenty sharp if it's reasonably new.

Poorer quality lenses tend to be fuzzy in the corners, and only when wide open. If you're going to be shooting a lot wide open, then you may want to check out reviews and see which perform the worst under that circumstance and avoid them.

Virtually any site that reviews camera lenses will have great charts and super-detailed analyses of sharpness.
 
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