We present HST /ACS imaging of twenty-three very low surface brightness ( \mu _ { e,V } \sim 25 - 27.5 ) galaxies detected in the fields of four nearby galaxy groups .
These objects were selected from deep optical imaging obtained with the Dragonfly Telephoto Array .
Seven are new discoveries , while most of the others had been identified previously in visual surveys of deep photographic plates and more recent surveys .
Few have previously been studied in detail .
From the ACS images , we measure distances to the galaxies using both the tip of the red giant branch method and the surface brightness fluctuations method .
We demonstrate that the two methods are consistent with each other in the regime where both can be applied .
The distances to 15 out of 20 galaxies with stable measurements are consistent with that of the targeted group within errors .
This suggests that assuming group membership based solely on projected proximity is \sim 75 % successful in this regime .
The galaxies are nearly round , with a median axis ratio of 0.85 , and visually resemble dwarf spheroidal galaxies .
The objects have a range of sizes , from R _ { e } = 0.4 kpc to R _ { e } = 1.8 kpc , with a median \langle R _ { e } \rangle = 1.0 kpc .
They range in luminosity from M _ { V } = -11.4 to M _ { V } = -15.6 , with a median \langle M _ { V } \rangle = -12.4 .
Galaxies with R _ { e } \sim 1 kpc and M _ { V } \sim - 12 are fairly rare in the Local Group but we find many of them in this relatively small sample .
Four of the objects fall in the class of ultra diffuse galaxies ( UDGs ) , with R _ { e } > 1.5 kpc and \mu _ { 0 ,V } > 24 \mathrm { mag arcsec ^ { -2 } } , including the recently identified dark matter deficient galaxy NGC 1052-DF2 .