To be specific we tested Elinchrom D-Lite RX 4 studio light (Amazon) and Yongnuo YN560 speedlite (Amazon). I wanted to know how speedlite compares to studio ligth. Speedlite was taped on top of the studio light to get similar conditions for both lights. With grey card in the picture ACR gives 5450K for the Elinchrome and 5950K for the Yongnuo. I used camera histogram to get similar exposures on both and it seemed that when Yongnuo was at full power (zoom 24mm) I had to put 4.2 (2.0 – 6.0) to the Elinchrome to get similar histogram. After that Elinchrom was put to the full power and light was moved farther. Yongnuo still in full power was matched with increasing ISO to 400. I have to say that cheapo speedlite is pretty capable light.