In the practice of the amateur photographer, the so-called. memory exposure tables for daylight and incandescent light. Each of them consists of two parts: first (I) — providing exposure in strictly defined conditions, and on the other (II) — discussing deviations from these conditions.
Here is a memory table of exposures for daylighting:
Part I
1. Panchromatic emulsion with a sensitivity of 20-21 DIN;
2. Sunny day, sky without clouds;
3. Item photographed in 50% illuminated by the direct rays of the sun, w 50% shady. (Np. side lit streets, when one side of them is in the shade);
4. For landscape, snowless landscape;
5. No higher than 1000 m above sea level;
6. Not earlier than on 2 hours after sunrise and no later than 2 hours before sunset;
7. Iris 1 : 16;
8. Snapshot 1/100 sek.
Attention!
The table is for films developed in an active developer. (Np. Fotopan Super film developed in a universal developer, diluted like paper, in temperature 18 °C, call time 220 sek. For D76 developers, we expose o 1 pitch more, for Atomal F - o 2 graduations more).
Part II
In this section, we will not specify the exposure times, only the number of divisions, which we need to move on the shutter scale, aperture, or both together. So instead of increasing the exposure fourfold, we recommend increasing the camera setting by 2 divisions - two on the aperture scale or two on the shutter scale, respectively one on the aperture scale and one on the shutter scale. So the illumination
are identical (within tolerance). Because the conditions given in part I change frequently, must change and the final result - exposure.
1. When changing the film sensitivity, the exposure corrections are as follows:
2. When there are clouds in the sky (cumulusy) reflecting light, but not blocking the direct rays of the sun - one division less.
When the sun is covered with light, transparent clouds, and objects still cast a perceptible shadow - one division more (hazy sun).
On a cloudy day - two divisions more.
On a gloomy day - 3 do 6 more pitches, depending on the darkness of the sky. The term "gloomy day" is very arbitrary. On such a day, the amount of light is difficult to assess "by eye". Therefore, it is better to illuminate more.
3. On a sunny day, an object in the shadow - illuminate o 1 pitch more.
Open spaces, beaches, big squares, by, meadows - o 1 pitch less.
At the seaside (and at sea) — o 2 do 3 less pitches.
Narrow streets, yards, park, rare forest - o 1 do 2 more pitches.
Interiors with large windows, not illuminated by direct rays of the sun - o 3 do 4 more pitches.
Dark interiors, dark forest - o 5 do 7 more pitches.
4. Snowy landscape, especially in the sun- 2 pitches less.
5. Above 1000 m above sea level, especially when the photographed space is exposed - o 1 pitch less.
6. In the period between the first and second hour after sunrise and the second and last hour before sunset - Fr 1 pitch more.
In the period from sunrise to the first hour after sunrise and the last hour before sunset - o 2 do 3 more pitches. About half an hour before sunrise and about half an hour after sunset, only on cloudless days 4 do 7 more pitches.
7. 8. Starting from Bunsen's formula - Roscoe E = it, where E - exposure, i - illuminance in lux, t - exposure time, we come to the conclusion, that the illuminance of the emulsion (aperture) balances the exposure time (snapshot). If, therefore, in the given conditions at the aperture 5,6 we should illuminate 1/250 sek., then the same photochemical effect will be obtained for a new type of snapshot scale:
