The progressive photographer must experiment, but his work is only that of proving up the claims of those who have done the real experimental work. He progresses because he does the minimum of experimenting, but he would get nowhere without at least trying out those things which seem to have advantages that may be of value to him in his work.

The users of Portrait Film are, for the most part, progressive photographers who have been quick to see the real value of the qualities claimed for film but sufficiently conservative to feel their way. That they have stuck to the use of film is conclusive proof that they have found it has brought them a step nearer the attainment of their ideals.

Month by month the sale of Eastman Portrait Film is increasing, in many instances is doubling, and while the increased sales are gratifying they mean much more than advertising, demonstrating and selling. Every blow of the hammer that drives a nail also tests the material of which the nail is made. If it's a poor nail it will crumple up and have to be withdrawn. If it's a good nail every blow of the hammer drives it deeper and imbeds it more firmly.

Portrait Film has proved itself. Four years of faithful performance in the hands of a growing list of progressive photographers has established it as a staple.

No one need say "Let the other fellow do the experimenting." That stage has long since been passed. Film sales are the best proof of performance, and when these sales continue to climb there is a very good reason.

Film performance should be of interest to every user of glass plates, for if better results are possible, the man who wants them should know what part his material plays in the quality of the result he secures.

Halation is the fault which has limited perfect reproduction. Halation is caused largely by reflections from the glass surface, very slightly by refraction within the emulsion itself. For the most part, therefore, it is the fault of the glass support and not of the emulsion. The reflection of light from the glass support can be overcome only in a measure and only at an additional expense in plate manufacturing.

The logical remedy for halation is the use of a support for the emulsion which, as nearly as possible, overcomes the defects of glass. As the extent of halation depends largely upon the thickness of the support, and this must be transparent, film is the logical and practical remedy.

Many photographers deny the existence of halation in their portrait negatives. This is because they have never seen a comparison between film and plate negatives. The film user enthuses over "that indescribable quality" he finds in film. He has been unable to see the halation in plates, but he can see the lack of it in the film result.

Masses of highlights without form are seldom natural and never to be desired, and form can not be produced without shade as well as light. Halation destroys the form of highlights, the texture of flesh, of delicate draperies - in fact, destroys any impression that is made up of a number of fine points of light with intervening shadows. The finer the detail the more surely will it be destroyed, for the spread of every point of light is determined by the thickness of the glass plate, and the finer the points of light the more surely will halation over-lap and destroy the intervening shadows.

True reproduction can not be secured where there is halation, but the more its effects are reduced the nearer will the result come to perfection. Film quality is superior because the most perfect emulsion that can be produced is coated upon a support so thin that it is practically free from halation.

Film negatives have the roundness, the brilliant crispness that one sees on the ground glass but so seldom gets in the finished print. Aside from these qualities Portrait Film has exceptional speed, fineness of grain and wide latitude. Its qualities are ideal for either studio or home portraiture, and the convenience of lightness, compactness, flexibility and ease of manipulation are very soon appreciated by the worker who is progressive and open to conviction.

Photographers who have given Eastman Portrait Film a thorough trial will tell you that the big advantages of film are "better results" - and convenience.