How to Spot a Faked QC Sheet

By Bon Zhan, Founder, Night Operators
Published: July 30, 2026 | Last updated: July 30, 2026

Why would anyone fake a QC sheet?

Because buyers started asking for them. For years the night vision market ran on model-level spec ranges and floor claims like "FOM 1400+", and the case for demanding a measured per-tube document instead has been made loudly enough, including by us in why per-tube QC sheets matter, that paperwork is now a selling point. Whenever paperwork becomes a selling point, somebody prints paperwork.

The good news is that faking a QC sheet convincingly is harder than it looks. A genuine sheet is the output of a physical measurement process, and measurement leaves fingerprints: consistent internal math, messy decimal values, plausible relationships between fields, and a serial number that ties the paper to one specific tube. A fabricated sheet is the output of someone typing numbers into a template, and typing leaves different fingerprints. This guide is about telling the two apart. Every check below uses a genuine reference: the real sheet from a shipped base-tier PVS-14, tube type 1803WB, which we walked through field by field in inside a real PVS-14 QC sheet.

What is the math check?

FOM is defined as resolution multiplied by SNR, which makes it the one field on the sheet you can audit with a calculator. Multiply the printed resolution by the printed SNR and compare the result to the printed FOM. On our genuine reference sheet: 65 lp/mm times SNR 20.33 gives about 1321, and the printed FOM reads 1301. The two numbers are close, and critically, the printed FOM is slightly lower than the multiplication.

That direction matters. Factories compute FOM from unrounded bench measurements before the resolution value is rounded for printing, so an honest sheet's printed FOM comes out at or slightly under the product of the printed figures. A small conservative gap is the signature of a real measurement chain.

The tell is the overshoot. When the printed FOM is meaningfully higher than printed resolution times printed SNR, the FOM was not produced by those two measurements, it was chosen. Someone picked the headline number the listing needed, then filled in supporting fields without doing the arithmetic. A sheet claiming FOM 2000 over figures that multiply to 1600 is not a measurement error; multiplication does not err by 25 percent. Treat any overshoot beyond rounding distance as disqualifying, and treat the whole document, and the seller who sent it, accordingly.

What are the template tells?

Fabricated sheets are built to look like paperwork rather than to record a measurement, and the shortcuts show.

Round numbers everywhere. Real test benches output values like SNR 20.33, uniformity 2.08, and sensitivity 519. A sheet reading SNR 25, gain 10000, and resolution 70 across the board has the texture of a wish list. One round value is chance; a full column of them is authorship.

Missing fields. SNR is the field most often absent, because SNR is the half of FOM that constrains the fake: print it and the math check becomes possible. A sheet that lists FOM and resolution but omits SNR has removed exactly the number that would let you audit it. Sensitivity and uniformity are the next most common omissions.

"Typical values." Those two words convert the entire document from a measurement of your tube into marketing for the model. A real QC sheet never needs them, because it describes one physical tube on one bench on one date.

No date, no stamp, no inspector. Real quality control is a process with accountability: a test date and a pass stamp or inspector mark. Their absence is not always fatal on its own, but combined with any other tell it usually is.

The same sheet twice. If you are buying two units, or comparing notes with another buyer of the same seller, and the sheets show identical values with different serials, you are looking at a template with a serial field, not two measurements. Real tubes differ; that is the entire reason per-tube sheets exist.

Why is the serial match the anchor check?

Every other check tests whether the sheet is internally honest. The serial check tests whether it belongs to your unit at all, and it is the check that catches the laziest and most common fraud: a genuine-looking sheet, possibly even a real one from a better tube, shipped alongside a unit it does not describe.

The serial printed on the QC sheet must match the serial on the tube itself, or on the housing where the builder records the installed tube's identity. When you receive a unit, find that engraving or label and compare it character by character. A missing serial on the sheet, a serial format that matches nothing on the device, or a seller who cannot tell you where on the unit to find the matching number are all versions of the same answer. This is also the single most important check when buying secondhand, where sheets and units have had years to drift apart; the wider checklist for that market is in buying used night vision.

What does a plausible zone map look like?

The blemish map counts dark spots in three concentric zones of the image circle. Fakers get it wrong in both directions.

Some omit it entirely, or compress it to a single "no defects" line, because a zone map is tedious to fabricate and most templates found online skip it. A missing map on a document claiming to be a full QC record is a strong tell.

Others overcorrect into impossible perfection: every unit the seller has ever listed reading zero spots in every zone, on tubes priced far below what blemish-free selection costs. Clean tubes genuinely exist, our reference 1803WB sheet reads 0 / 0 / 0 across all three zones, but across a whole inventory, spotless zone 3 on every single unit at bottom-tier prices describes a selection process the price could not fund. Plausibility is about the fleet, not the unit: real production shows variation, and honest sellers ship sheets that show it, including the occasional small zone 3 count sold as exactly what it is.

The same plausibility logic applies across fields. A sheet pairing Gen 2+ pricing with sensitivity figures that only Gen 3 photocathodes produce, or claiming top-shelf FOM on a bottom-shelf listing, is describing a tube that would never be sold at that price. When paper and price disagree, believe the price. The generation-level numbers that make these claims checkable are laid out in Gen 2 vs Gen 3: FOM and SNR.

What should you do when a sheet fails a check?

Stop, in the practical sense: do not pay, or if you have paid, start the return clock immediately and put your findings in writing to the seller. Be specific: "the printed FOM of 2000 exceeds the printed resolution times SNR, which multiply to 1600" is a sentence a payment processor and a dispute reviewer can follow. Photograph the sheet, the serial engraving, and the listing claims before anything else happens.

Give the seller one honest out: sheets are occasionally mismatched by clerical error in a real warehouse, and a legitimate seller responds to a serial mismatch by producing the correct sheet quickly and without friction. What a legitimate seller never does is argue that the math check does not apply, explain that the values are "typical", or promise the tube performs better than its own paperwork. The moment the defense of the document requires redefining the document, you have your answer, and a first dark-night verification of the unit itself will usually confirm it.

Frequently asked questions

How do I check if a night vision QC sheet is fake?

Run five checks: multiply printed resolution by printed SNR and confirm the result lands at or slightly above the printed FOM; look for messy bench decimals rather than round numbers; match the sheet's serial to the tube or housing; confirm all core fields are present including SNR and a three-zone blemish map; and sanity-check the claimed performance against the price. A genuine sheet passes all five in minutes.

What is the FOM math check?

FOM equals resolution multiplied by SNR, so the printed figures must agree with each other. On a genuine sheet the printed FOM sits at or slightly below the product of printed resolution and SNR, because factories compute FOM from unrounded measurements. A printed FOM meaningfully higher than the multiplication means the number was chosen rather than measured, and the sheet should be rejected.

Why do real QC sheets have such odd decimal values?

Because they record instrument readings, and instruments do not produce round numbers. A real bench outputs values like SNR 20.33, uniformity 2.08, and sensitivity 519 uA/lm. A sheet where every field lands on a tidy round figure has the texture of a filled-in template rather than a measurement record.

What if the sheet has no serial number?

Treat it as a model-level flyer, not a QC sheet. The entire value of the document is that it describes one specific tube, and the serial number is the link that makes that true. Without a serial, or with a serial that matches nothing on the unit, the sheet proves only that the seller owns a printer.

Which field do faked sheets most often leave out?

SNR, because printing it enables the math check against FOM. Sheets that list an impressive FOM and a resolution figure but quietly omit SNR have removed exactly the number that would expose an overshoot. The blemish zone map is the next most common omission, since it is tedious to fabricate convincingly.

Are all-zero blemish maps fake?

No, genuinely clean tubes exist, and a single sheet reading zero spots in all three zones can be perfectly real. The suspicion belongs at inventory level: a seller whose every unit reads spotless in every zone at low prices is describing a tube selection their pricing could not pay for. Real production shows variation, and honest paperwork shows it too.

Can a real QC sheet be shipped with the wrong unit?

Yes, both by clerical error and by intent, which is why the serial match is the anchor check. Compare the sheet's serial to the engraving on the tube or housing character by character. An honest seller fixes a mismatch by producing the correct sheet quickly; evasion or excuses about the mismatch are their own answer.

What should I do if I already paid and the sheet fails the checks?

Document everything immediately: photograph the sheet, the unit's serial, and the original listing claims, then contact the seller in writing with the specific failure, such as the FOM exceeding resolution times SNR. Start the return process inside your window. Specific, arithmetic-based complaints are the kind that payment disputes and marketplace claims resolve in the buyer's favor.