Sherlock Holmes In Pencil

I did a pencil sketch of Robert Downey Jr. as Sherlock Holmes as part of my Law and Order brief from photo reference, I wanted to study his features accurately to get a good likeness in this drawing. It took a considerable amount of time to get it to the point i was happy with. I would like to re-create this image again if i had the time and re-work it to make it perfect, i used hair-spray to preserve it step by step so that it wouldn't transfer onto the other pages in my sketch book but this meant I couldn't erase and re-work certain areas i wasn't happy with when i decided i wanted to have another go at them, next time I would try to get everything to a point I could work more detail into and that i'm pleased with before spraying it. I have created other portraits like this one, and they take me a very long time to create, i would like to look into some loose pencil sketches next and not focus so heavily on detail.