The Dictionary Of Photography

A True Historic Record Of The Art & Practice Of Photography 100 Years Ago.

Home | About | Photography | Contact

may be useful, as very fine results may be obtained from taking a portrait ot anybody engaged at work, or seated by the fire, or reading, writing, etc., and in such cases the picture would be in-complete without the actual and necessary furniture in the room, and in this case, too, we may admit the otherwise inadmissible wall paper. Without going to any outlay, a capital background, especially for children, is the screen to be found in so many houses, and the same may also serve for the support of a ready-made background which may be found in every house - namely, a blanket; or the screen may be used to support the reflector. We may use either a portrait lens or, as these when of good quality are costly, we may get what is perhaps the next best lens for portraiture, and that is the single lens of fairly long focus, working at rather a larger aperture than usual - viz., There is sufficient spherical aberration present with such an aperture, as a rule, as to have no baneful influence and yet give us roundness and softness. Personally, we have rigged up a compromise, and that is as follows. We managed to get hold of some unmounted single or meniscus landscape lenses, and we use these in a mount specially made for us, and we are thus able by a little calculation to obtain any focal length and any ratio aperture we want. The lenses are of 22, 18, 16, 13, 10, and 8 in. focus respectively. We had a tube of brass made with a cell to fit in each end ; into these cells we can slip any one of the above lenses, and a ring of brass keeps the lens in its place. The tube isins. long, and the cells screw in till there is only two inches between the inner surfaces of the lenses. The diaphragm slot is just midway. Now, according to the well-known rule, multiply the foci of the two combinations together, and divide by the sum obtained by adding them together and subtracting the distance of separation, it is quite possible to reckon out any focus we like. Let us take, for instance, the 22 and 18-in. lenses -
focal length. Now, the full aper-ture of our lens is if ; t efore we get a focal length of io£ ins. and a ratio aperture ofat which there is sufficient outstand-
ing spherical aberration to give us softness. Or we may use the