I’ve Been Wondering About All Of The Third Party Lenses We Have Been Seeing Over The Past Few Years…

Azalea during Spring bloom. (click to enlarge)
Nikon Z7; Nikkor 24-70mm f/4 S lens @ 70mm; 1/125th sec. @ f/5.6; ISO 400

Do you really know what you are getting in the way of resolving power when you buy an inexpensive third party lens?  I’m not sure I do.

I think I know what the major camera manufacturers are creating when it comes to new lenses for their digital camera lineup.  We can justifiably assume (and I know assumptions can be dangerous) that when Sony, Canon, Nikon or Fuji takes years to design, engineer and produce a new, high megapixel camera, that the lenses they produce from a certain date forward (before or at the time they decide to produce a camera with a certain number of pixels), are designed to fully take advantage of all of the available detail the new sensor in that future camera can resolve.  In other words, long before a new, high megapixel camera is introduced, those major manufacturers are taking into account all of the additional pixels their lenses will have to resolve and start to design or redesign their lens lineup to be able to resolve all of the extra detail.  But what about all of those third party lenses?  I find it is hard to believe that a $399 US lens can resolve 45, 50 or 61mp.

When Nikon first introduced the 36mp D800 and D800E, Nikon commented on their existing lenses abilities to resolve all those pixels.  I don't remember exactly what was said but I remember the discussion on the Internet about it.  When Fujifilm recently introduced their new 40.2mp APS-C sensor in 2022, there was a lot of buzz about their older lenses not being able to take full advantage of the new sensor’s resolution.  However, the lenses they had introduced over the past couple of years (knowing the new sensor was coming) could.  They even put out a list of which lenses could realize "maximum benefit" from the new sensor.  (Andreas Georghaides, Fujifilm UK Marketing Manager stated on a Fujicast Podcast about 18 months  ago that the earlier Fujfilm lenses were designed to resolve "up to 32mp." So all of Fujifilm's older lenses can resolve up to 32mp, which is an improvement over the 26mp sensors in Fujifilm’s existing cameras).  But if you want to realize all 40.2mp, you need to buy one of the lenses on their list.  At least we know.  That is a good thing.  But what about all of those third party lenses out there?

At what resolution do Sigma’s, Tamron’s, Tokina’s and all of the Chinese and Korean independent lens maker’s lenses perform?  How many pixels can they actually resolve?  Are you essentially throwing away those additional pixels you so dearly paid for because these inexpensive lenses can’t resolve all of those megapixels in the new cameras?  No one seems to be asking those questions that I’ve seen.  We don't know or at least I don’t know.  I don't remember seeing anything stating at what level any of these lenses can resolve detail.  If I've missed it, please comment and let us all know.  

According to Roger Cicala (as stated in a podcast), founder of LensRentals.com, many of these “new” lenses from these small independent manufacturers are actually from lens formulas that are very old, in fact, developed for film cameras decades ago.  So old the patents have long ago expired.  That is how they can produce and sell them so inexpensively.  Being that the lens formulas were developed without computer assistance with less sophisticated glass, how much can they resolve?  Now they can be sharp, but still not resolve what your camera's sensor is capable of recording.

I don't believe the three major independent lens makers—Sigma, Tamron and Tokina—use those old formulas, but how many of their new lenses are just reworked mounts for different cameras but using the same basic formulas from before high megapixel cameras existed?  I think this would mostly refer to some of their older zoom lenses as their new primes seem to be excellent optics by all accounts.  But why aren't they telling us how many pixels these lenses are capable of resolving?  Again, if I've missed a specific number of pixels touted, let me know.

When I see tests for these low cost independent lenses conducted on YouTube or the Internet, generally they are tested for being sharp in the center, edges and corners.  Also they may be tested for AF speed, consistency and accuracy.  Some go as far as to also test for aberrations, vignetting and distortion.  However I don't see any in-depth resolution testing.  Yes, we sometimes see some charts with line-pairs, but no real measurement or mention of actual resolving power.  If we are lucky we might see some ‘theoretical’ MTF charts.  But those are theoretical values, not necessarily real world values.

So my questions remain, “How many pixels can these inexpensive lenses resolve and do they perform to the level of resolving all of the detail in your new high megapixel camera or are you short-changing yourself by buying one of them?  Are you unknowingly losing resolution for the sake of buying an inexpensive, independently manufactured lens?  I just don't know.

Over the decades, I've bought, used and have been pleased with a number of independent manufactured lenses.  However, once I bought my Nikon D800E, I almost always stayed strictly to the camera manufacturer's lenses as I wanted to ensure I could see all of the detail that my camera's sensor could render.  That said, I'm not saying not to buy these lenses.  Most of them are very sharp and focus quickly.  Certainly, I wouldn’t hesitate to buy a new Sigma or Tamron lens.  

Some photographers feel that a lens’ ‘charateristics’ are the most important factor when purchasing a lens.  By characteristics I mean how a lens renders an image in ways other than just sharpness or resolution.  I have no issues with that whatsoever.  That said, these inexpensive lenses most likely will suit the needs of most of those photographers.

There are a number of parameters that affect image quality—ability to sharply render an image close-up, mid-range and at infinity, overall sharpness, resolution, contrast, color rendition, vignetting, distortion and correction of aberrations.  (any more?)  Without going down the technical rabbit hole too far, a lens can be sharply focused and not have the ability to resolve more than, for example, 20mp of detail.  Also, a lens can record 45mp of resolution, be sharp when focused in the center but soft on the edges due to field curvature but make you think it is of low resolution.  

Sharpness and resolution, although closely intertwined, are separate factors in lens performance.  Sharpness tends to measure how well a lens focuses edges.  For example, on test charts ‘line pairs' are used to test focus and resolution.  Line pairs are increasingly smaller and smaller pairs of short black lines separated by a tiny bit of white space.  Sharpness will measure how distinct the edges of the black lines are shown while resolution will determine how small of a white space can be clearly rendered and still be distinct between the black lines.  Contrast also plays a role but, as I said, I don’t want to get too technical.

To wrap this up, my point in this post is back to the question “do you really know how much resolution you are getting when you buy one of those inexpensive third party lenses?”  If not, are you potentially short changing yourself and degrading the ability of your very costly camera with its 45mp, 50mp or 61mp sensor?  If resolving all of the pixels in your new camera is not a major concern to you, then you have nothing to worry about.  Excellent!

For whatever reason these are the kinds of things that pop into my 'strange' mind.  I just wanted to give your something else think about.

Join me over at my website, https://www.dennismook.com.  

Thanks for looking. Enjoy!  

Dennis A. Mook  

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