LXK0930 Loc: Souh Jersey

I have read that the "Sweet Spot" for prime (fixed) lenses is generally about 2 stops down from the lens's maximum aperture.
What about for zoom lenses, where the maximum aperture decreases as you zoom?

photosbytw Loc: Blue Ridge Mountains

Be your own judge. Use a tripod or a solid surface. Set your camera to AV and start at the maximum, or narrowest end, of the lens's aperture and work your way (up or down) if you have the capability to compare the images, side by side. This way, you know where "your" lens sweet spot is. When testing a zoom repeat the above-mentioned test at different focal lengths.

This will eliminate the "generally" portion equation.

camerapapi Loc: Miami, Fl.

I would follow the advise of photosbytw if indeed you want to know the "sweet spot" of your lens. When using a zoom what I do is testing the lens mainly at the longest and shorter zoom ranges. Let's say I am using a zoom like the Nikon 18-200 f3.5-5.6 VR. I test the lens at 18mm closing that couple of stops from f3.5, around f8 I would say and then I do the same with the 200mm focal length, I close a couple of openings from f5.6 to around f11. Those should be the "sweet spots" of the lens.

Testing is always necessary to really familiarize with the performance of the lens.

CHG_CANON Loc: the Windy City

If you paid $2000 for a mirrorless version of a 50mm f/1.2 lens, would you believe an internet urban legend about that lens being sharper around f/2.8? Or, would you look at focus charts for that specific lens and various user reviews and example results? Testing information showing the lens is as sharp wide-open at f/1.2 as any smaller aperture?

If you paid $1700 for an older DSLR style 24-70mm f/2.8 lens, would you believe an internet urban legend about that lens being sharper around f/5.6? Or, would you look at focus charts for that specific lens and various user reviews and example results? Testing information showing the lens is as sharp wide-open at f/2.8 as any smaller aperture?

You might scoff bringing pro-grade equipment into a discussion of internet rumors, but look at a chart from a $300 typical consumer-grade DX kit lens, the Nikon AF-S DX NIKKOR 55-200mm f/4-5.6G ED VR II. That green color shows the lens is a good wide open through 1-stop down as the aperture gets smaller and the focal length longer. Your internet rumor for f/11 at 200mm doesn't match the DXOMark testing results.



Some internet urban legends are next to impossible to undo. Does any of this reply seem more logical in Feb 2023 than an age-old internet rule-of-thumb about sweet spots and 1- or 2-stops down?

awesome14 Loc: UK

If you have a photo printer, you can print test targets. Or you can purchase test targets, but they're in the hundreds of dollars range. I printed my own, and they work very well. I set up in the basement. Aim the lens, turn off all ligjts, lock up the mirror and open the shutter, and then use flash for the correct duration.

I use asa 100, test all the stops up to 16, test 3-4 focal lengths on a zoon, 2 of which are the extremes. The best zoom I ever tested was a Nikon 200-400 AF ED VR G. What a superb piece of glass. Nothing will resolve the whole target, but that lens was all sweet spot up to f/11.

I'm not a big fan of zooms. You lose a lot more shots with them. And it isn't that much footwork to do your own zooming. Wide zoom ranges all suck! Hate to say it, but you just can't put that much into a lens and still get good performance.

One of my goto for indoor candids is a zoom, though, a 24-120 f/4 that looks great at f/4 on 24 and 120. It's kind of a heavy clunk for what it is, but it outperforms almost everything in it's class. I shoot in vivid color mode if I'm doing jpgs, and that works perfect on that setting. It adds life to dead objects.

I also use it a lot for eBay.com photos. The better the photos of a nice looking item, the more you'll get for it. I frequently get more on a sale than I originally paid for an item. I've sold about $50,000 worth of stuff on ebay since I joined. You can make money on stuff you don't want. The last time I had a problem was at least 20 years ago.

I can pretty much look at a zooms range and tell you if it's any good.

Manglesphoto Loc: 70 miles south of St.Louis

Just shoot the photos!! Most people will never know if you hit "The sweet Spot" including you!

Bill_de Loc: US

We used to tape a newspaper the wall as a target and do just what you suggest. Now, all we have to do is go on the internet and ask others how well our lenses work. It is a good thing since newspapers are getting scarce.

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agillot

Usually around f8 ???

LXK0930 Loc: Souh Jersey

My question was more of an academic inquiry than looking for a practical solution.
I am a (very) senior, and have more important things to do with my remaining time..... like figuring out it I am tying or untying my shoes.

CHG_CANON Loc: the Windy City

Do academic questions begin with accepting the 'common knowledge' of internet urban legends as established facts?

Architect1776 Loc: In my mind

Depends on the lens.
The Canon R135mm f1.8 L was just reviewed and was flawlessly sharp etc. at f1.8 as stopped down to diffraction limit.
Other lenses do better if pixel peeping at a smaller aperture than wide open.
For me this is totally a non issue as aperture is used to obtain DOF either shallow or deeper.

robert43 Loc: Auburn, CA

TriX Loc: Raleigh, NC

Testing is the only way to answer this question. That old adage of “Two stops down from wide open” is often inaccurate. If you don’t want to take the time to check your lenses (which doesn’t take long), you can look up tests for many lenses online.

Bridges Loc: Memphis, Charleston SC, now Nazareth PA

Testing as you prescribe is the way to go. It would be hard to label a lens sharp at any f-stop without individual testing. Lenses are made within a certain tolerance at the factory and one lens might be at the lower end of acceptable while another might be at the upper end. I once read about one pro that each time he wanted a new lens would order three of the same lens, test each one, and keep the one he felt was the sharpest, returning the other two.

Canisdirus

Depends on the lens...as always.

The goal is...to find the lens you need...that has no real sweet spot...great out of the gate...only falling to diffraction at f/16 or something.

That's the holy grail....and they 'usually' cost a pretty penny.

Quality almost always involves increased cost.