Why are there less optical abnormalities with a prime lens?

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Cameron T said:
Here's my opinion, we've long hit the point where 'sharpness' (especially for web use) is more than good enough with even lower zooms for most of the frame. What mainly you get with primes is smoother bokeh, thinner dof, more light gathering ability, and even more sharpness, but often at 3x+ the cost once you cover the focal range of the zoom (or nearly).
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And better distortion / aberration performance.
 
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I'm not even so sure that's really true. I mean, okay, to a point, but when lenses like the 180-600 already have very low distortion/aberration, it feels nitpicky to talk about.
 
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Sure the best prime at a given focal length may beat the best zoome at a given focal length in image quality. I feel this misses two key points though. First mirrorless zooms are often as good as primes from the DSLR days, so the noticeable image quality gap has gotten smaller and smaller. Second, you miss all the shots you can't get due to having the wrong focal length prime on.

Personally, I like high IQ lenses and flexible zooms. I am a big fan of the CV APO lenses for when I can go slow and take my time. Their IQ is some of the best available. But I have also been enjoying the Nikon 28-400mm for when I know I will be missing photos if I have to change lenses. The Nikon 24-400mm is about as sharp at f8 as my Nikon 24-120mm f4 is at f4 but this is a big difference in 120mm vs 400mm.

We have more quality lens choices as photographers than ever. I say use the gear helps you get the images you want to capture and that you enjoy using. Lens testing is useful for evaluating new gear and learning about your gear's strengths and weaknesses. At the end of the day though photography is all about capturing a moment and sometimes the best tool can even be the phone in your pocket.
 
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DigitalWorldOfPaul said:
Sure the best prime at a given focal length may beat the best zoome at a given focal length in image quality. I feel this misses two key points though. First mirrorless zooms are often as good as primes from the DSLR days, so the noticeable image quality gap has gotten smaller and smaller. Second, you miss all the shots you can't get due to having the wrong focal length prime on.
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True, if you're into faster shooting genres. I'm mostly a landscape shooter who typically gets there early, so I'm not often in that kind of hurry.

Though I still see people carrying 2 bodies with different focal lengths, myself included. When I go to a faster-moving event, I can usually pick a couple that will cover most things; so I'm not missing much, if anything.

DigitalWorldOfPaul said:
Personally, I like high IQ lenses and flexible zooms. I am a big fan of the CV APO lenses for when I can go slow and take my time. Their IQ is some of the best available. But I have also been enjoying the Nikon 28-400mm for when I know I will be missing photos if I have to change lenses. The Nikon 24-400mm is about as sharp at f8 as my Nikon 24-120mm f4 is at f4 but this is a big difference in 120mm vs 400mm.

We have more quality lens choices as photographers than ever. I say use the gear helps you get the images you want to capture and that you enjoy using. Lens testing is useful for evaluating new gear and learning about your gear's strengths and weaknesses. At the end of the day though photography is all about capturing a moment and sometimes the best tool can even be the phone in your pocket.
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Absolutely. All of my posts in this thread relate to the OPs opening question—there's a still difference, and it's up to the individual to decide if the small IQ gain is worth the loss of flexibility.

Chris
 
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DigitalWorldOfPaul said:
I am far from an optics expert, but my understanding is when making a prime lens the lens designers are able to optimize for a specific focal length, when making a zoom lens the lens designers need to make tradeoffs throughout the zoom range to produce a balanced result. For example, a 24-70 zoom may trade off some sharpness at 70mm to produce acceptable sharpness at 50mm. Next faster lenses are usually sharper when stepped down. For example, an f1.8 prime might be sharper at f2.8 than a prime lens that is wide open at f2.8. Lastly, pricer optics usually have the best glass, lens coatings, and quality assurance. For example, the Nikon 14-24 f2.8 S has the Nikon Arneo coat, which the Nikon 14-30mm f4 does not.

Some extremely high IQ lenses, like the Voigtlander APO lenses also trade AF for MF to help optimize IQ in a small package.

Rember through that lens, like a lot of electronics, have a point of diminishing returns. I think it's safe to to say the Nikon 50mm f1.2 S is better than the Nikon 50mm f1.8 S but, unless f1.2 is critical for your use it's hard to say the f1.2 lens is 3.5x (the price difference) better than the f1.8 lens. Also, the f1.2 lens is larger and heavier, so it may not be as practical for your needs.
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The Z 50 1.2 S may have better rendering and Bokeh, but it is not necessarily sharper than the Z 50 1.8 S. The MTFs shows the 50 1.8S is actually slightly sharper centrally. That's not putting down the 50 1.2, it just shows how good a 50 1.8 can be on Z mount.
 
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maxxus46 said:
The Z 50 1.2 S may have better rendering and Bokeh, but it is not necessarily sharper than the Z 50 1.8 S. The MTFs shows the 50 1.8S is actually slightly sharper centrally. That's not putting down the 50 1.2, it just shows how good a 50 1.8 can be on Z mount.
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The funny thing is that by comparison, the older F-mount versions of the 50mm f/1.4 and 50mm f/1.8 were very average in terms of sharpness. They were still popular because they were very small lenses and reasonably priced, but sharpness - especially across the frame - was not a strength compared to other primes. If you wanted 50mm, none of the F-mount 24-70 lenses were the best choice either. They were generally very sharp at the center of the frame, but not to midframe and corners.

The Z lenses changed all this. The Z 24-70 f/4 is very good compared to anything for F-mount, and the f/2.8 version is another step up. Still - the zooms don't compare to the primes as clearly evidenced in MTF charts. The 50mm primes have moved from average to outstanding - both the Z f/1.8 and f/1.2 primes. Clearly there is a change in design priorities placing more emphasis on sharpness. The other change is the backgrounds are not always as good as some of the older lenses. There are some specific Z prime lenses designed for smooth backgrounds, but those designs don't necessarily seek to improve sharpness further. That's a very good approach for portraits where ultimate sharpness is not desired and bokeh is much more important.

For wildlife, the game changes. Sharpness and the ability to render detail is critical. As you would expect, the $10,000+ telephoto prime lens is sharper and faster than the prosumer zooms designed for pricing at $2500 and less. In every case the more expensive primes are sharper and faster. But at the prosumer end, quality has continued to improve as well and differences are harder to see. I think most people will find the exotic primes to be sharper, but it requires high magnification to see the difference. The big difference is toward the corners at faster apertures. The difference in backgrounds and the bokeh is much more obvious as you can readily see a difference between the 600 f/4 backgrounds and the 180-600 f/6.3 backgrounds. These differences are even more apparent with cropping or when you add teleconverters.

I think at this time the difference is sharpness is relatively unimportant, but the wide open aperture, midframe to corner sharpness, and the bokeh differences stand out across prime comparisons as well as zoom comparisons.
 
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EricBowles said:
The funny thing is that by comparison, the older F-mount versions of the 50mm f/1.4 and 50mm f/1.8 were very average in terms of sharpness. They were still popular because they were very small lenses and reasonably priced, but sharpness - especially across the frame - was not a strength compared to other primes. If you wanted 50mm, none of the F-mount 24-70 lenses were the best choice either. They were generally very sharp at the center of the frame, but not to midframe and corners.
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The Nikon 50mm f1.4 G was my first f1.4 lens and I used it on my D7000. Price was the main factor at the time. Eventually, I went FF and got the Sigma 50mm F1.4 art after it came out. The Sigma was about 2.5x the size, weight, and cost, but optically it was much better.

I also have the 24-70 f2.8 G. At the time it was the best mid range zoom you could get. But I no longer use it for photos requiring edge to edge sharpness. My Nikon Z 24-120mm f4 is sharper across the frame at f4 then my 24-70 f2.8 G is at f4. Zooms have definitely come a long way. The Nikon 14-24mm f2.8 G was one of my favorite lenses, but there is no denying the Nikon 14-24 f2.8 Z is better in every way.

As a side note, it does seem like some lenses have traded center frame sharpness for edge to edge sharpness. Personally, I like this approach, since you don't have to place your subject in the sharpest zone and it helps your corners not look as soft as the center, which was amplified when the center was supper sharp and the corners were fairly soft.
 
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