<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2022-03-16</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001046995</issuerCik>
        <issuerName>EMAGIN CORP</issuerName>
        <issuerTradingSymbol>EMAN</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001230770</rptOwnerCik>
            <rptOwnerName>GINOLA LTD</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O INPENDRA LIMITED, 2ND FLOOR</rptOwnerStreet1>
            <rptOwnerStreet2>EATON HOUSE, 9 SEATON PLACE</rptOwnerStreet2>
            <rptOwnerCity>ST. HELIER</rptOwnerCity>
            <rptOwnerState>Y9</rptOwnerState>
            <rptOwnerZipCode>JE4 9WG</rptOwnerZipCode>
            <rptOwnerStateDescription>JERSEY</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2022-03-16</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>6900</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>1.1082</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>63101</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2022-03-17</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>5800</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>1.1610</value>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>57301</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2022-03-16</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>36700</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>1.1159</value>
                    <footnoteId id="F3"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>373231</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Flat Creek Fiduciary Management LLC, as Trustee</value>
                    <footnoteId id="F5"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2022-03-17</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>19700</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>1.1628</value>
                    <footnoteId id="F4"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>353531</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Flat Creek Fiduciary Management LLC, as Trustee</value>
                    <footnoteId id="F5"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>78478</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Mount Union Corp.</value>
                    <footnoteId id="F6"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>57372</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Chelsea Trust Company, as Trustee</value>
                    <footnoteId id="F7"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">The price reported in Column 4 is a weighted average price. These shares of Common Stock, par value $0.001 per share (&quot;Common Stock&quot;), of eMagin Corporation (the &quot;Issuer&quot;) were sold in multiple transactions at prices ranging from $1.08 to $1.14 per share of Common Stock, inclusive. Ginola Limited (&quot;Ginola&quot; or the &quot;Reporting Person&quot;) undertakes to provide, upon request, to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission full information regarding the number of shares of Common Stock sold at each separate price within the ranges set forth herein.</footnote>
        <footnote id="F2">The price reported in Column 4 is a weighted average price. These shares of Common Stock were sold in multiple transactions at prices ranging from $1.14 to $1.18 per share of Common Stock of the Issuer, inclusive. The Reporting Person undertakes to provide, upon request, to the Issuer, any security holder of the Issuer, or the staff of the SEC full information regarding the number of shares of Common Stock sold at each separate price within the ranges set forth herein.</footnote>
        <footnote id="F3">The price reported in Column 4 is a weighted average price. These shares of Common Stock were sold in multiple transactions at prices ranging from $1.085 to $1.145 per share of Common Stock of the Issuer, inclusive. Flat Creek Fiduciary Management LLC, as Trustee, undertakes to provide, upon request, to the Issuer, any security holder of the Issuer, or the staff of the SEC full information regarding the number of shares of Common Stock sold at each separate price within the ranges set forth herein.</footnote>
        <footnote id="F4">The price reported in Column 4 is a weighted average price. These shares of Common Stock were sold in multiple transactions at prices ranging from $1.13 to $1.185 per share of Common Stock of the Issuer, inclusive. Flat Creek Fiduciary Management LLC, as Trustee, undertakes to provide, upon request, to the Issuer, any security holder of the Issuer, or the staff of the SEC full information regarding the number of shares of Common Stock sold at each separate price within the ranges set forth herein.</footnote>
        <footnote id="F5">These securities are solely owned by Flat Creek Fiduciary Management LLC, as Trustee. The Reporting Person disclaims beneficial ownership of these securities, and this Form 4 shall not be deemed an admission that the Reporting Person is the beneficial owner of these securities.</footnote>
        <footnote id="F6">These securities are solely owned by Mount Union Corp. The Reporting Person disclaims beneficial ownership of these securities, and this Form 4 shall not be deemed an admission that the Reporting Person is the beneficial owner of these securities.</footnote>
        <footnote id="F7">These securities are solely owned by Chelsea Trust Company Limited, as Trustee. The Reporting Person disclaims beneficial ownership of these securities, and this Form 4 shall not be deemed an admission that the Reporting Person is the beneficial owner of these securities.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Sumantha R. Sedor, Attorney-in-Fact</signatureName>
        <signatureDate>2022-03-18</signatureDate>
    </ownerSignature>
</ownershipDocument>
