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The Optical Magic Lantern Journal and Photographic Enlarger.
the strip is fully printed I substitute another, and when the second is done I know my lantern slide is finished. An image is visible upon it, and can be seen by opening the printing frame at the back, but I prefer to work entirely with this simple form of actinometer.
Nothing remains but to develop the slide by immersing it in cold water, in which it may be left until the image is fully out. If the slide has been a trifle over-printed it is reduced by being left in the water overnight. I prefer, however, not to do this, but to develop it under atap of running water. It speedily takes on a fine blue tone, which although I have heard it said is not permanent, I have not discovered to be wanting in this respect. Some slides I made in 1891 in this way are still as vigorous as the day on which they were produced. I prefer to use a little acetic acid (1 drop per 2 ounces) in the last washing water, as it brightens up the colour considerably.
The Development of Lantern Slides.
By T. PERKINS. VZa | \ HERE is a certain amount of difficulty
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\ for lantern slides whether they are } made by contact or reduction. If one has a dozen slides to make from the same number of negatives great difference in the exposure may be necessary on account of the different densities and colour of the negatives, and it by no means follows, even if one is fortunate enough to hit on the correct exposure for the first, that this will indicate, without the chance of failure, the correct exposure for the second.
I have lately made some hundreds of slides for lecture purposes from negatives taken at wide intervals of time, developed in very different ways, and as I did not wish to have as many failures as successes, I hit on a plan which has reduced the number of failures to a minimum. I may say that all the subjects were architectural, in which a considerable variety of colour in the slides is not only allowable but desirable, and though one aims at a: black colour for a building such as Exeter Cathedral Church, and a red one for such a church as that at Lichfield, with various shades of brown .for most subjects, yet if we get Exeter a little too warm and Lichfield a little too .cold, the slides if otherwise good are
a in determining the correct exposure |! iy 4
not rendered worthless on account of their not being quite of the ideal colour aimed at,
My method of proceeding is to mix up two cups of developer, one the normal developer for cold tones (I have lately been using some most convenient and economical ready-made solutions, prepared by Mr. Baynton, of New Street, Birmingham, from a formula by Mr. Harold Baker), and another which will give warm tones, provided a long enough exposure is given, owing to the addition of a certain amount of a combined solution of bromide of ammonium and carbonate of ammonium—one ounce of each dissolved in twenty ounces of water. The more of this that is added to the normal developer for black tones, if it is somewhat diluted with water, and a longer exposure given, the warmer will the tone become.
My method of using is as follows:—I give.a full exposure, so as to make certain of not losing a slide from under-exposure, and pour on the developer calculated to give warm tones. In this the image appears slowly in any case’; but if from the fact that after several minutes have elapsed without any image at all appearing, I conclude that the exposure has
| for this developer, I pour it off, and apply the
other made for producing black tones. This never fails to start development. If the image comes up too quickly the plate goes back into the re-strained bath, and it may be that it can be finished in it; but it-may be necessary once more to apply the other solution to urge on development once more. By skilfully ‘alternating the two developers an excellent slide may be produced, and its tone will lie between those that would be produced by each of the two developers if used alone.
It may be asked what must be done should it be found that the slide has received too long an exposure even for the re-strained bath in which it is first placed? This is not very likely to occur; but the difficulty may be met, should it occur, by baving ready for use a third developer, containing a still larger proportion of the bromide and carbonate of ammonium.
Tt must not be supposed that a fresh mixing of developer is required for each plate; there are few developers used for slides in which at least half a dozen plates may not be developed in succession. My practice is to prepare two ounces of the re-strained developer and one of the stronger one. Two slides are : generally developed together in the former in a half-plate developing dish, and if necessary they are taken out one at a time to be put into the forcing