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SHARPNESS vs. F/STOP

Remember how similar the lenses looked to each other on my sharpness pages at each f/stop? That's because most lenses perform almost identically to other similar lenses at any given f/stop.

On the other hand, lens sharpness varies wildly with aperture. I chose the 50mm f/1.4 AI for this example. Any of the other f/1.4 lenses would do the same thing. I chose the 55 Micro for f/32 because the f/1.4 lenses don't go to f/32.

Guide Image.

1.4 AI at f/1.4	1.4 AI at f/2	1.4 AI at f/5.6	1.4 AI at f/16	55 AI-s at f/32

SUMMARY

Your choice of aperture is far more important than your choice of lens!

Lens performance varies wildly from one f/stop to the next.

It's easy to make mistakes when comparing lenses. If you compare at different f/stops you're not comparing lenses. Many laypeople make the mistake of comparing two lenses at different times of day, or different f/stops. Any time you change anything in your test, you're no longer comparing two lenses.

Most lenses are their sharpest from two stops below maximum to about f/8. Avoid apertures smaller than f/8 because diffraction softens them.

f/1.4 lenses are very sharp from f/2.8 onwards, while slower zooms may have a much smaller range of optimum apertures. Luckily good zooms are quite sharp wide open, unlike most f/1.4 lenses.

PLUG

I spent almost two months shooting and writing this comparison of 50mm lenses. No one pays me for this. If you find this as helpful as a book you might have had to buy or a workshop you may have had to take, feel free to help me write more with a donation.

Thanks for reading!

Ken

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