The open cluster IC 4996 in Cygnus and its vicinity are investigated by applying a two-dimensional photometric classification of stars measured in the Vilnius seven-color photometric system .
Cluster members are identified by applying distances based on the Gaia DR2 parallaxes and the point vector diagram of the Gaia DR2 proper motions .
For some B-type stars , spectroscopic MK types are also obtained from the Asiago spectra and collected from the literature .
New parameters of the cluster are derived .
The interstellar extinction A _ { V } covers a wide range of values , from 1.3 to 2.4 mag ; the mean value in the central part of the cluster is 1.8 mag .
The cluster distance is 1915 \pm 110 pc , and its age is within 8–10 Myr .
The cluster exhibits a long sequence from early-B to G stars , where stars cooler than B8 are in the pre-main-sequence stage .
The plot of extinction versus distance shows a steep rise of A _ { V } up to 1.6 mag at 700–800 pc , which is probably related to dust clouds at the edge of the Great Cygnus Rift .
The next increase in extinction by an additional 0.8 mag at d \geq 1.7 kpc is probably related to the associations Cyg OB1 and Cyg OB3 .
The cluster IC 4996 does not belong to the Cyg OB1 association , which is located closer to the Sun , at 1682 \pm 116 pc .
It seems likely that the cluster and the surrounding O-B stars have a common origin with the nearby association Cyg OB3 since Gaia data show that these stellar groups are located at a similar distance .