He moved to Dresden and on New Year's Eve of 1875 married Marie Therese (née Grafe) with whom he turned his mother-in-law's haberdashery store into a thriving business.

Living frugally, by 1888 they had saved 7,500 marks with which Ernemann purchased a share in carpenter Wilhelm Franz Matthias's camera shop on Pirnaer Strasse in Eschdorf, establishing himself in the still-nascent photo industry.

Recognising and developing the market for such goods, he gave their small backyard workshop the brand 'Dresden photographic apparatus factory,' producing bespoke portable and studio cameras.

Moving into larger premises in 1892 Ernemann then introduced steam power, contriving an operating structure necessary for industrial mass production and machinists to reduce dependence on suppliers for small metal parts.

Entrepreneur and inventor Fridolin Kretzschmar had in 1902, prior to Ernemann, devised and sold his 17.5mm Kinematograph camera intended for the low end of the professional market.

His son Alexander, who in America had become expert in industrial efficiency, joined the company as technical manager in 1904 and restructured it, introducing quality control and a system of apprenticeships.

Their Imperator, a durable 35mm movie projector made from steel, an engineering advance on flimsy and unreliable existing models, was launched at the first International Photographic Exhibition, 'a collective representation of Photography in all its branches and in all civilised countries,' held in Dresden (on the board which, Ernemann served with Hugo Erfurth, C. P. Goerz, Dr. Adolf Miethe, Dr. Richard Neuhauss, and others)[12] and was quickly taken up by almost all cinemas in Paris.

Increasing expenditure on its 400 employees, plant and advertising caused financial strain but a mooted merger with ICA was avoided and after the company recovered quickly in 1910, Ernemann was knighted in the Order of Albrecht (First Class).

The 1922/23 period of hyperinflation, during which the company produced for the government the 50 million Deutschmarks voucher, was followed by recovery and expansion of the Schandauer buildings to accommodate the then 3,500 workers, then a recession that halved that number.

Max Bruenner, writing on the Dresden industry in the American photo magazine Photo-Era in 1923 remarked:What reader has not heard of the firm of Ernemann, which sends its products to all parts of the world?

[2] Ernemann's wife Marie Therese had passed away on 22 August 1917, and eleven years later, he died aged 78 on 16 May 1928 in his summer villa Heinrichs Eck at 21 Am Hartheberg in the spa town of Hartha, built in 1900 and since restored.

[24][25][26] He was survived by his children Frieda Henriette Marie Therese (1876–1954), Alexander Karl Heinrich (1878–1956), Anna Katharina Gertrud (1880–1940), Dora Bertha Johanna (1883–1942) and Fritz Henry Otto (1886–1941).