Thirty-four 35mm primes, twenty-five standard zooms. Each row carries weight, size, price new, price used, and two letter grades — corner sharpness and build — drawn from published reviews rather than first-hand measurement. Fifty-nine rows in total.
Correlations run across that set produce three findings that hold up and one common assumption that does not.
The full dataset is browsable as an interactive comparator, where adjusting the priority weightings rearranges the ranking. What follows is one reading of it.
Price to sharpness correlation
The expected result was diminishing returns — a brand tax above some threshold, with cheap options performing close to expensive ones. The primes do not behave that way.
Price against corner-sharpness grade across all 34 primes gives a correlation of 0.75. That is strong. Spending more does buy a sharper 35mm lens, reliably enough that the grade is close to predictable from the price.
Zooms are looser at 0.61. Still a real relationship, but with more slack in it — more room to overpay, and more room to find something underpriced. A zoom has more ways to be good or bad than a prime does, and price tracks only some of them.
| Relationship | Primes | Zooms |
|---|---|---|
| Price → sharpness grade | r = 0.75 (n = 34) | r = 0.61 (n = 24) |
| Aperture → weight | r = −0.70 (n = 34) | r = −0.34 (n = 25) |
Negative aperture correlation means faster glass is heavier, because a smaller f-number is a bigger opening. For primes the tax is steep and consistent. For zooms it barely holds, since a zoom's weight is driven more by how far it zooms than by how fast it opens.
Lowest-cost A-grade lenses
Nine primes in the set carry an A or A− for corner sharpness. The cheapest is the Viltrox AF 35mm f/1.8 II EVO Apo at about $395 used, 355 g. Next is the Sigma 35mm f/2 DG DN Contemporary, $450, 325 g. The most expensive A-grade prime in the whole set is the Sigma 35mm f/1.2 Art at $1,050. More than twice the money for the same letter on the sharpness column, and 765 g of extra weight for the f/1.2 aperture.
Past that point the money is not buying sharpness. It is buying aperture, which is a separate attribute that happens to arrive bundled with the same letter grade.
Zooms tell a similar story with a clearer bargain at the front. Twelve are graded A or A−. The cheapest is the Tamron 28–75mm f/2.8 G2 at $620 used, 540 g. The most expensive is Sony's 28–70mm f/2 GM at $2,450 and 918 g. Four times the price. One grade step, if that.
First-party price premium
Comparing like grade against like grade, first-party against third-party, on used prices:
| Set | Grade | Sony, median | Third-party, median |
|---|---|---|---|
| Primes | A | $1,050 (n = 1) | $875 (n = 6) |
| Primes | B+ | $520 (n = 1) | $300 (n = 5) |
| Zooms | A | $2,100 (n = 2) | $1,075 (n = 2) |
| Zooms | A− | $1,015 (n = 4) | $800 (n = 4) |
| Zooms | B+ | $1,300 (n = 1) | $490 (n = 6) |
The sample sizes matter more than the medians. Several cells contain a single lens, which makes them a data point rather than a median. The pattern across all five rows points the same direction: Sony costs somewhere between slightly more and roughly double for an equivalent sharpness grade. The data does not support a more precise figure than that.
Grades also cannot capture autofocus reliability, firmware support, or resale liquidity — the attributes that most often motivate a first-party purchase. The dataset has nothing to say about them.
Manual versus autofocus pricing
The intuition worth testing is that manual-focus glass functions as a discount: no motor, comparable optics, lower price. The 34 primes split 23 autofocus to 11 manual, and the medians do not support it.
| Focus | Count | Median used | Median sharpness | Median build | Median weight |
|---|---|---|---|---|---|
| Autofocus | 23 | $450 | 4.20 (B+) | 4.20 (B+) | 426 g |
| Manual | 11 | $250 | 2.70 (C+) | 3.30 (B−) | 360 g |
The manual group is cheaper, but gives up a full grade and a half of sharpness to get there. That median is pulled down by cheap manual primes — Pergear, Meike, AstrHori, all under $150 — and pulled up by the Voigtländer APO-Lanthar, an A at $850 and one of the best lenses in the set. The median describes a bimodal population, and so describes neither half of it well.
What survives is narrower: cheap manual focus is cheap because the glass is worse, not because the motor was omitted. Good manual focus costs roughly what good autofocus costs. The expected discount is not present.
Size as a selection criterion
A common compact-kit shortlist pairs the Sony Sonnar 35mm f/2.8 ZA with the Sigma 28–70mm f/2.8 Contemporary, both selected primarily for size. The data supports one of those choices and undercuts the other.
On size the Sonnar wins outright: 120 g, 36.5 mm long, second-shortest and second-lightest of all 34 primes, beaten only by the Samyang 35mm f/2.8 at 85 g. As an object to carry it is close to unbeatable.
Filtering for primes that are sharper than it and still under 300 g returns three:
- Tamron 35mm f/2.8 Di III OSD — B+, 210 g, $210 used
- Samyang AF 35mm f/1.8 — B+, 210 g, $260 used
- Sony FE 35mm f/1.8 — B+, 280 g, $520 used
The Sonnar is a B at $430. The Tamron is a full grade sharper for less than half the money, at a 90 g weight penalty — roughly the weight of a set of keys.
The size argument for the Sonnar therefore holds only in its narrow form. Where a lens must fit in a jacket pocket, 36.5 mm is the shortest length that still performs acceptably, and that length has real value. Where the requirement is only low weight, the premium is being paid for a form factor rather than for optical performance.
The Sigma zoom survives the same scrutiny. At 470 g it is fourth-lightest of the fifteen f/2.8 standard zooms, $620 used, B+ on both grades. Against the Sony 24–70 GM II it is 225 g lighter and $1,130 cheaper, giving up one sharpness grade and the 24 mm end. The three f/2.8 zooms lighter than it either lose the telephoto reach (Tamron 20–40) or cost more (Sony 24–50 G), and the Thypoch 24–50 has not shipped.
Cheap manual focus is cheap because the glass is worse, not because the motor was omitted.
Method and limitations
The sharpness and build columns are not measurements. They are letter grades synthesised from published reviews — Alik Griffin's lens list, phillipreeve.net, DustinAbbott, OpticalLimits, Cameralabs, DPReview, plus manufacturer specifications. Reviewer consensus, converted to letters, then converted to numbers on a scale where A = 5.0 and C− = 1.8 so that correlations could be run at all.
That conversion is the weakest link in everything above. The gaps between letter grades are not equal in reality, and the numeric scale treats them as if they were. Every correlation on this page inherits that assumption. The direction of each finding should survive it; the second decimal place should not be relied on.
Prices are ballpark US street prices as of mid-2026 — new from the usual retailers, used from MPB, KEH and eBay in good condition. Used prices move constantly and in some cases vary by more than the differences these conclusions rest on.
- Character lenses grade badly on purpose. The Voigtländer Nokton Classic gets a C+ for corner sharpness and people buy it precisely for how it renders. Same for the Laowa Argus f/0.95. A clinical sharpness column cannot capture the reason those lenses exist.
- Superzooms get the same unfair treatment. The 24–240 is a C+ and it is also the only lens here that covers 24 to 240.
- Sample size undercuts the Sony-versus-third-party table badly. Three of five rows have a single Sony lens in them.
- APS-C lenses are excluded, as are 16–35 ultra-wides and 70–200 teles. Standard zooms only.
- No copy-to-copy variation is accounted for anywhere. Published reviews test one sample too.
The open question is whether the price-to-sharpness relationship would hold against real MTF data instead of graded consensus. It would most likely weaken: reviewers know what a lens costs when they review it, and that knowledge plausibly leaks into the grade. This dataset cannot test for that, and it is the factor most likely to make the headline correlation overstated.