Digital Camera Photography Frame and Focus

The relationship between two sides of the image never coincides with that of the two sides of the paper. In the darkroom we analyze the frame more carefully. If the frame we made with the camera seems better, we can enlarge all the negative in a sheet of paper; if not, we can use the sheet to reframe the image, eliminating details we aren't interested in. The correct focus of the negative on a sheet of paper is vital to obtain images of a better technical quality. It is a matter of fixing it in every print we make. In many cases it is difficult to focus at plain sight on the base of the enlarger: in low definition images or ones with too much density. A negative is focused in strict sense, when we can see the emulsions grain on the base of the enlarger. Our eye doesn't have the resolution power to see it in a dark room but it does on a print. Therefore, in the darkroom, the use of a enlarger magnifying glass is almost indispensable, which lets us see if the emulsion is effectively focused. Focus is made at maximum diaphragm aperture and without a red filter. For exposure, an intermediate aperture on the scale is recommended, which provides maximum sharpness and a good focus depth, we can use the numbering of the film as reference and expose the print with a small aperture. Each image can have very variable characteristics. Observing the enlarged negative on the base, we can examine it's characteristics, as we have seen in 11.7, to decide the contrast of the paper we are going to use.

Choosing the Papers Characteristic Contrast

We saw that the contrast of a print depends on the enlarging, meaning: the characteristic contrast of the paper chosen and the exposure level. Throughout 4.3 we have represented the operation of the emulsion as a ladder of growing densities according to the exposure level. With an original brightness interval and an exposure value, the interval of exposure levels is placed somewhere along the horizontal axis; this gives way to, after developing, the formation of a determined negative density interval . Now, with the developed negative in the negative holder, we have a second photograph, where the "original" brightness are the ones transmitted with the different densities of the image, and where the considered emulsions that of the photographic paper. Depending on the exposure level, the density interval of the negative is going to be placed in some position along the horizontal axis. This is the same reasoning we make with the camera, only now we can choose the shape of the ladder .

Lets imagine for an instant that there is only normal contrast paper, were the density interval of the negative is reproduced with a similar contrast in the print, further down (towards white) or up (towards black) according to the exposure level. If the image in the negative holder reproduces the original scene as a different density scale and of normal contrast, then the technical quality of the negative is reproduced with no difficulty. If the contrast of the negative is excessively high or low, the normal paper reproduces this characteristic.

In a very contrasted negative, the density interval may exceed what can be registered in detain in the print. The exposure level necessary to register lights with detail is incompatible with the detail in the shadows and vice versa. If the contrast of the original scene has increased a lot in the negative, a printing on normal paper will give us excessive contrast, different from the original scene . Some zones with detail in the negative appear indistinctly white or black in the print.

In a low contrast negative, the density interval of the negative can be very reduced: whatever we do with the exposure level, the original brightness levels of the scene are going to appear as very similar densities on a print with normal contrast paper. If the contrast of the original scene has been too reduced in the negative, on the print the aspect will be flat, and the different zones appear in a medium density, with no blacks or whites.

The choice of a characteristic contrast in the paper is different than normal and allows us to compensate the excess or the defect in the contrast of a developed negative. In all the degrees of contrast, the ends of the tonal range are the same: black and white:. If we made a test giving different exposures to strips of paper of different characteristic contrast, we would see that in these tests we pass from white to black in an exposure level interval that is narrower the greater the contrast (4.3.2). Therefore, it is necessary to have in account the exposure latitude of the paper, which varies with the characteristic contrast. If the latitude expresses the brightness interval of the original that "fits" in the registration capacity of our film, now the negative is an interval of densities that may or may not fit with detail in a print.

We can express the exposure latitude of the paper as the maximum relation of density between the lights and shadows of the negative were it is possible to have detail in the print:

If we use this table in practice, we can be sure that is a determined exposure level (=1) causes a barely detectable effect on the paper's emulsion ( white , underexposure limit), the black is reached for a level 32 times greater than in the case of a contrast number 0 paper and for a level only five times greater than in a contrast paper number 5.

Now we can clearly see that a very contrasted negative doesn't "fit" in the latitude of normal paper, but can be perfectly registered on a softer paper, of greater latitude. Analogously, the densities of a low contrast negative are usually low resolution. A very contrasted paper accentuates the slight density differences and reproduces them as greater differences; starting from a reduced density interval in the negative produces a greater tonal separation. The contrast degree is the shape of the gray ladder we are using. It is a new variable which lets us have great control in the image's characteristics, and also correct mistakes or excesses in contrast of an image. When considering the exposure level, it is necessary to not only take in account the density of the main zone, but also the ones corresponding to the lights and shadows for this type of paper .