"stopped down a bit the lens sharpens right up"

Almost no lens is at it's best wide open, right? From what you read in general I suppose most require a full stop down. So that means you pretty much never get to use your pricey L lenses wide open.

On average does a f/1.2 or f/1.4 need to be closed to f/2, does a f/2.8 need to be closed to f/4, does a f/4 need to be closed to f/5,6?


C.

"Need to", no, not in the sense that you'll get unusable pictures when you shoot wide open. However I don't know of any lens, prime or zoom, from any manufacturer, that won't gain a little in resolution by being stopped down 1-2 stops below its' fastest aperture.

Just because a lens gets sharper when it is stopped down does not mean that it isn't sharp enough when it is wide open. I'm comfortable with all of my lenses wide open, and I typically stop down for reasons of DOF, not sharpness.

Also, you need to keep in mind that some lenses are lousy wide open, and still lousy stopped down (but less lousy) while some lenses simply go from great wide open to incredible stopped down. I'm happy with my 50L wide open, even though it does indeed get better stopped down. I used to have a 50/1.4 that was good stopped down but unusable really much below about f/2. It just got all dreamy at f/1.4.

Quick example I can think of, compare the Canon 24-70 II wide open with the Canon 28/1.8 stopped down 1 and 1/3 stops to f/2.8. The zoom is better. That one addresses two bits of common wisdom in one step.....primes are not always sharper than zooms, and a stopped down lens is not always better than a different lens wide open.

If you go outside of Canon, some Leica lenses are even better examples of where a 'slow' lens can be so good wide open that it is better than some faster options stopped down.

My 300mm 2.8L II doesnt need to be stopped down to get extremely sharp picture. I dont see any different at all in sharpness between 2.8 and 4.

Another lens is my 100-400mm II. Maybe I'm just lucky to get super sharp copy. I always use it exclusively wide open, never stop down because I dont gain anything in sharpness.

chuckmiller wrote in post #17824751
Almost no lens is at it's best wide open, right? From what you read in general I suppose most require a full stop down. So that means you pretty much never get to use your pricey L lenses wide open.

On average does a f/1.2 or f/1.4 need to be closed to f/2, does a f/2.8 need to be closed to f/4, does a f/4 need to be closed to f/5,6?


C.

True. Almost no lens is at its best wide open.
False. Most lenses are at their best at around two stops from wide open.

The rest of your logic is flawed. Your car is most efficient at around 45 mile per hour. Do you only drive it at that speed? Your furnace is most efficient when it is cold enough outside to make it stay on all the time, say about -20F. I'm guessing you don't wait for -20F temps to turn it on. Your gait is most efficient at a fast sprint. Walking is less sweaty. Best performance and usable performance are not the same thing.

There is a good article on this at https://www.learn.usa.​canon.com …ensaperture_art​icle.htmlp. The important thing is there is no hard and fast rules. Each lens may have its "sweet spot" thjat defy the rules. But if the optimum image quality for you is both needed and desired, then you should probably set up some tests. They aren't hard to do. I would suggest a newspaper page as the subject and you need a tripod and a remote way of releasing the shutter (or use the timer). I'd use manual focus and magnified live view. You might also find some differences based on subject distance.

Stopping down a lens sharpens it up. But how sharp do you need? What does your camera require? My 17-40 is plenty sharp at f/5.6 on the 5d, but I wont use it below f/8 on the 60d.

We can lust all day at the sharpest lenses just as we can lust after the fastest supercars. But usually, we're not going above highway speeds. Or: usually we won't blow up a picture to monstrous dimension and expect it to be crazy sharp.

Bit of the old "you get what you pay for"

A cheap lens "generally" will have a more noticeable effect from stopping down than the higher dollar lens, which is why their are "L" lenses.

Aus.Morgo wrote in post #17825120
Bit of the old "you get what you pay for"

A cheap lens "generally" will have a more noticeable effect from stopping down than the higher dollar lens, which is why their are "L" lenses.

Yep. The 24L II's big game is in its ability to do f/1.4. It is generally considered to be crap at the edges wide open. It is the sharpest lens Canon makes at f/4 & f/5.6. My 18-55 STM can do sharp at 24mm and f/5.6. It can't do squat at f/1.4. If I had the money, I'd have a 24L II. Don't really give a hoot about the perimeter at f/1.4.

Yes, generally most lens provide their highest resolution about one or two f/stops from their maximums. I think that digitai super high ISOs have mislead today's photographer about the REAL purpose of very large apertures...to GET THE SHOT!

In the days of ISO 400 film, in certain light you simply could NOT get the shot handheld and without flash, so being able to open a lens to f/1.2 or f/1.4 allowed a shot to be successfully taken, while a shot at f/2.8 might not be possible without excessive camera shake or subject motion. So 'inferior' resolution was accepted as a necessary but inevitable result.

Three of my Prime lenses I shoot the majority of the time wide open. (200f/2, 85f/1.2 v2 and 135f/2) The images they produce are tack sharp wide open. I only stop down when DOF needs to be considered. However, my 24-70 f/2.8 v2 and 70-200 f/2.8 v2 are marginally better when stopped down. With regards to sharpness I consider my prime lenses better than my zooms.

I think that you miss the point when it comes to the L's. They give you the brightest image in the viewfinder, the color rendition and contrast are beautiful and you won't have to upgrade as often when your new body out resolutions your prosumer lens. I rarely shoot wide open but do come close but the DOF is so shallow and my clients need to promote their products.

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chuckmiller wrote in post #17824751
Almost no lens is at it's best wide open, right? From what you read in general I suppose most require a full stop down. So that means you pretty much never get to use your pricey L lenses wide open.

It seems like you are thinking that if a lens is at its very, very "test chart best" stopped down one full stop, that that is then the only way that discriminating photographers are going to use the lens. . That thinking is just not true.

The "pricey L lenses" that you mention happen to be the ones that are extremely sharp wide open at their widest aperture. .This is most notable in the new L series offerings; those that have been updated within the past 8 years or so. .I often shoot alongside some of the world's most picky, discriminating wildlife photographers, and they shoot their "pricey L lenses" wide open on a continual, constant basis.

The new 600mm f4 is absolutely tack - no, razor sharp - wide open at f4.

Ditto for the new 500mm f4.

Even the lowly new 100-400mm zoom is absolutely razor sharp wide open at f5.6!

So actually, it is the very "pricey L lenses" that you call into question that are an exception to the "rule". . The cheaper, "not so pricey" lenses are the ones that typically have to be stopped down in order to obtain professional level sharpness. These would typically be Canon's older L series lenses*, Canon's non-L series lenses, and third party lenses.

*There are, of course, exceptions.
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All Canon L lenses are pricey. Some are STUPID pricey.

chuckmiller wrote in post #17825997
All Canon L lenses are pricey. Some are STUPID pricey.

Does this mean you are not a Leica shooter?