How to develop black and white or color photos at home?

1 plastic or metal developing tank

More than 2 reels of suitable size

3 Lid opener (used to open 35mm film cassette)

4 pairs of canned scissors

5 developers

6 Stop shadow liquid (optional)

7 fixed solution

Two or three containers are used to hold developer, fixer (if used) and fixer, and are usually used to measure the volume of solution.

Two sealable liquid storage tanks for storing developer and fixing agent.

10 A stirring rod or stirrer used to prepare a solution.

1 1 darkroom thermometer

12 plastic bucket

13 wetting agent

14 haibo cleaning agent or water washing accelerator

15 heavy and light movie clips

16 darkroom timer

17 medium-sized plastic funnel

18 envelopes or film bags for film archiving

19 darkroom (if there is no ready-made darkroom)

Developing tanks made of stainless steel or synthetic materials have various sizes. Steel tank is easy to conduct heat, while synthetic tank can better insulate heat and resist the temperature change of solution caused by external temperature change. Several film axes should be suitable for all general film addition sizes. In order to clean multiple rolls at the same time, several film shafts can be driven simultaneously in a larger developing tank.

An effective darkroom timer should be accurate and easy to read quickly. Both analog and digital timers can be used. Select the time display mode you like.

Make obvious marks on the container to prevent the wrong order of use.

In order to obtain the best quality, the developer recommended by the film manufacturer should be selected. Manufacturers often recommend several developers at the same time, so it is advisable to choose a developer whose packaging capacity is just enough to meet the needs, so as to avoid wasting and trying to develop the developer with a time shorter than 4 minutes, because it is inconvenient to pour the developer into the developing tank in such a short time and the development uniformity is not good.

Some developers call it a one-time trial, which will be discarded after one use. Other developers can be used for a period of time, and their chemical components can be supplemented according to the formula and reused. If a small amount of film is developed occasionally, disposable developer can avoid storage and loss problems; At the same time, it can produce high-quality and high-density negatives. Replenishable developer is most suitable for developing a large number of films frequently, which is very economical. Some developers can be used twice or once after dilution. Or directly use the stock solution, while constantly adding supplementary solution.

Commonly used Kodak developers include Kodak HC- 1 10 developer, Kodak D-76 developer and Kodak MICRODOL-X developer. HC- 1 10 and D-76 developers can give full play to the sensitivity and dark details of the negative film, with normal contrast and fine particles. The negative film produced by MICRODOL-X developer is very fine, but it has little effect on the sensitivity of most films. The effect of Kodak HOBBY-PAC black-and-white film development kit is similar to that of HC- 1 10 developer, and the kit is very convenient to use.

◆ Safety first.

Care must be taken when using all chemicals, including photographic chemicals. Wearing protective gloves can prevent direct contact between skin and photographic chemicals. Specific knowledge of chemical safety operation can usually be obtained from product labels or product labels or raw material safety instructions.

It must be carried out in strict accordance with the requirements of liquid preparation, and the powdered developer should be stirred gently in the liquid. If bubbles are mixed in the solution, it will lead to premature oxidation of the developer and weaken its developing function. Fixing solution and fixing solution can be prepared at present. When adding powdered fixing agent to warm water, slowly add powder while stirring. If it is added too quickly, it will form a hard lump, which will not dissolve easily for a while.

Bottles for storing chemical liquids should be dedicated for a long time and labeled accordingly. If necessary, after thorough cleaning, the original bottle can be modified with stop-shadow solution or fixing solution, but the developer can not be stored in the original bottle, because the developer will contact with the trace stop-shadow solution or fixing solution left in the bottle for a long time, which will reduce its function.

Store the unused or partially used liquid medicine, fill the container and seal it at room temperature. This is especially important for developers. When the developer comes into contact with air, the developer will quickly age due to the oxidation of air. Squeezable plastic bottle is the most ideal container for storing developer, which can be folded to discharge air above the liquid level of the solution. Other liquid drugs can be preserved with ordinary bottles.

The name of the chemical liquid in the liquid storage bottle should be marked and the preparation date should be named. The recommended storage time is usually several weeks or months, and expired drugs should be discarded, because drugs have largely lost their original functions. Some chemicals, especially fixative and fixative, can be recycled and tried again and again. It is necessary to refer to the maximum working capacity data of drugs provided by manufacturers, and do not let drugs "extend their service".

It is best to store photographic chemicals in a cool place. If the climate is cold, don't store the medicine in a place with low temperature. Too low temperature will cause some chemical components to precipitate or short circuit in the solution, and these precipitates or crystals cannot be reduced to the solution.

The time and temperature of film development should be strictly controlled, so that the development effect can be repeated, accurate timing is easy to achieve, and accurate temperature control is often difficult.

If the developer temperature is too high, the film will be overdeveloped, and if the developer temperature is too low, the film will be underdeveloped. Most black and white developers use development temperatures of 20 degrees Celsius and 24 degrees Celsius, depending on the specific film. The development time listed in Kodak black-and-white film materials often refers to the data at 18 degrees Celsius, 2 1 degrees Celsius and 22 degrees Celsius. If the development temperature you choose is close to the ambient temperature of the darkroom, it is easier to adjust the temperature. Ideally, all the washing liquid, washing water and developer have the same temperature. In fact, the temperature of other liquid drugs is 3 degrees Celsius higher or lower than that of the developer.

In order to make the liquid medicine reach a suitable temperature, a deep dish or barrel can be used as a water bath. According to the need of heating or cooling the liquid medicine, the bath temperature of the water pool can be adjusted to a few degrees higher or lower than the temperature that the liquid medicine should reach, and then the liquid medicine or the measuring cup with the pre-measured liquid medicine is put into the water bath until the liquid medicine temperature reaches the required temperature. At this time, if necessary, the temperature of the water bath should be adjusted to the temperature corresponding to the flushing temperature. When the amount of liquid in the water bath is relatively large, the temperature change will be relatively small, which can prevent the temperature of relatively small chemical liquids around from changing sharply.

There are many kinds of darkroom thermometers, and the best one is accurate and can respond quickly to small temperature changes. In addition, the scale of the thermometer should be easy to see.

The temperature of the flowing water used to clean the film can be adjusted by thermostatic valve. If there is no such device in the darkroom, it is necessary to manually adjust the amount of cold and hot water, measure the water temperature with a sensitive darkroom thermometer, and prepare a bucket of water with the right temperature for use when the temperature of the water flowing from the faucet is out of control.

Most developing tanks only need a room or other completely dark environment when loading films. In order to check whether the temporary darkroom is dark enough, you can put a piece of white paper on the workbench where the film is taken, just like when you really want to load the film. Then close the door. Block the light leakage. Wait in the dark for at least 5 minutes. If you can't see the blank paper after 5 minutes, it means that the place is dark enough, or you can put the film in a dark bag, so there is no need for a dark room.

In a darkroom, or when using a dark bag, put the developing tank, lid, reel, cassette, cassette or lid opener (if necessary) and scissors (if necessary) in order, so that you can know where to put these things. The biggest object of a tank is a good sign. At this time, you can close the door or cover the dark bag.

Open the 35mm film cassette and take out the film:

Use a cap opener to pry open the cap on the protruding end of the spindle. Take out the film core from the film box and cut the film title from the film with scissors.

Turn the exposed end of the film cartridge in the direction of marking, and separate the cartridge to take out the end of the cartridge. You can take out the roll film and backing paper of 135 by separating the cassette. In order to take out 135 film, you should slowly unload the film and backing paper from the cassette, and make sure that the backing paper is stuck on the edge of the cassette, not the film, and then separate the film from the backing paper and load it.

According to the requirements of the manufacturer, the film should be wound into a reel in a dark room or a special dark bag. When you touch the end of the film, cut off the film attached to the reel with scissors. If it is a film fixed with adhesive tape, it is easy to tear it off, but it must be torn slowly to avoid tearing the film or generating electrostatic sparks. Then, put the film in the slot, cover it, and then you can turn on the light or take out the developing slot from the dark bag.

Before turning off the lights every time, arrange the developing tank, cover, reel, scissors, film, cassette and cover opener in the same order, so as to find the required items in the darkroom or dark bag.

Wrap the metal sheet with a metal shaft

When winding the film, only touch the edge of the film to avoid leaving fingerprints on the screen.

Remember that the whole operation process must be carried out in complete darkness. If you are not familiar with the operation of putting and loading films, you should first practice in a dark room with used waste films.

Stainless steel spiral reels are usually wound from the inside out. And the new reel is generally rolled from the outside to the inside. The loading instructions must be strictly observed to ensure that the film can be successfully loaded on the specified film track. When there is abnormal resistance or fluctuation, rewind the film a few inches and try again. Time is here, so that the film can smoothly enter the film track. Make sure that the hands and spindles are completely dry.

For 135 film, use scissors to disconnect the end reel, and for film with one end fixed on the reel with tape, carefully tear the tape from the film.

◆ Use plastic shaft winding parts.

Some plastic sheets must be inserted into the spiral film path from the outside to the inside. Make sure that the reel is completely dry before loading. Because wet spots on the film path will make film insertion difficult, you must follow the manufacturer's film loading instructions carefully.

The developing tank is stirred at specified time intervals to ensure the uniformity of development. The specific mixing time sequence varies with the combination of film and developer. A typical stirring procedure is to beat the bottom of the tank after the development starts, so that the tank can move directly up and down in reverse, and the bubbles adsorbed on the film emulsion are discharged. Then stir 15 seconds, stir for 5 seconds after 30 seconds of initial appearance, and then stir for 5 seconds every 30 seconds. The developing tank with good sealing performance can be turned up and down and stirred along the tank axis, and repeated twice every 5 seconds.

It is best to move smoothly. In fact, consistency in operation is more important than operation itself. However, excessive agitation should be avoided, otherwise it will lead to excessive development. Insufficient stirring will cause uneven development and insufficient development.

If the darkroom temperature is slightly higher or lower than the developer temperature, the developer tank should be put into the water bath during the intermission of stirring to maintain the appropriate washing temperature.

If possible, start developing in a darkroom, put one or more reels into a container filled with developer, and keep the proper temperature. Generally, this method can obtain the best uniform development. Start the timer, cover the developing tank and turn on the light.

If this method is not suitable for you, you can cover it first, then develop it in a bright room, and pour the developer into the tank through the light-shielding baffle on the cover of the developing tank. As long as the tank body is slightly inclined, most developing tanks can easily pour out the liquid medicine. Start timing when the liquid medicine is full, and then cover it with a small cover to block the liquid injection port.

When you use a developing tank that can hold multiple rolls, be sure to put enough empty rolls on the roll with film, so as to prevent the roll with film from shifting during development, measure the developer volume that is enough to fill the developing tank, and pour it into the tank, so that the film to be developed can be completely filled and the developer should also be filled into the developing tank.

If the developing tank can be turned upside down without spilling liquid, it can be turned upside down while rotating around the tank axis. Be sure to grasp the small cover above the tank to prevent it from opening suddenly.

The developing tank without a small cover cannot be inverted. Sliding back and forth about 10 inch (25 cm) twice per second can partially swing, and the developing tank can rotate half a turn in all directions. The development time recommended by the manufacturer is suitable for most people in most cases. However, if you find that the film is always thicker (deeper) or thinner (shallower) than required, you should first check your exposure meter and camera to make sure the exposure is correct. If the exposure is really normal, then the negative is always too thick or too thin, which is caused by the developing equipment or method. You can shorten or extend the development time of the negative according to your own wishes, so that the photos can get satisfactory results. When you do experiments to determine the deployment time, change the deployment time within the range of 10%, and don't deviate too far.

Furthermore, if the development time is too long, the printed photos will easily cause coarse particles and excessive contrast, so the development time should be reduced until the normal contrast is obtained.

For negatives with too dull picture and too little contrast, it is necessary to increase the development time to make the picture more glorious.

It is subjective to identify the quality of negative film with naked eyes, even by experts. Therefore, we should not only visually inspect the negative film, but also jump to conclusions and change the development conditions. The first thing to consider is the quality of photos made from negatives. To some extent, it is more important to observe photos with eyes than to look at negatives. If you can easily take high-quality photos with negative film, it means there is no need to change the development conditions of negative film.

At the end of the development time, open the liquid injection port on the tank (do not remove the cover) and start pouring out the developer. Start pouring developer in advance. So that when the timer indicates the end of development, the developing tank is just emptied, and the reflow time is about 5-20 seconds, which varies according to the developing tank used by everyone. Remember how long it takes to fill the developing tank you use each time.

◆ Stop displaying or clean with water.

According to the manufacturer's instructions, inject the diluted solution into the developing tank and shake it vigorously for 30 seconds or a special time. Its function is to stop developing, wash off the residual developer on the film and the developing tank, and pour out the developer for recycling. Because the developer is acidic, it can neutralize the developer faster than washing, and it also helps to prevent the developer from being brought into the fixing solution. If you plan to develop a large number of films and reuse the fixing solution, it is worth considering to use the stopping solution. The capacity of most fixing solutions depends on the use of stopping solution.

◆ Fixed

Pour the fixing solution, adjust the timer to the required time, and fully stir until the fixing time is over, then pour out the fixing solution. If necessary, recycle it. Fixing solution should be at the same temperature as developer.

◆ Cleaning of film

In order to prevent the degradation of film image quality in the future, before drying, a small amount of fixing solution must be washed with clear water to wash off the residual fixing solution on the film. It is necessary to continuously let water flow down from the center of the film axis in the open developing tank, and then flow out from the spiral film tank to wash away the fixing solution. Normally, 20 minutes of fixing solution washing is enough. It is best to check the washing time recommended by the film manufacturer.

Hang the film in a clean, dust-free and ventilated place to facilitate the drying of the film. Put a heavy clip on the bottom of the film and straighten it. After hanging the film, directly wet the fingers of one hand with diluted wetting solution, then gently wipe the film between the two fingers with two fingers, and gently squeeze the film from both sides. This is a method that can remove moisture from the surface of the film, and the risk of scratching the film is minimal. In order to dry faster, you can also carefully wipe the film with a soft sponge or sheepskin. Sponge and sheepskin should be soaked in diluted wetting solution first, and then squeezed out.

This is a bathroom with bathtub and shower, which can be used as a dust-free and secluded place to take pictures. Pay attention to put a clip at the bottom of the film to prevent the film from curling during drying.

The drying time varies greatly with the relative temperature. If quick drying is needed, a drying oven with thermal cycle and air filter can be used. This kind of drying box has different specifications. If you have the right tools at hand, you can also make one yourself. If quick drying is only needed occasionally, you can use a portable hair dryer.

◆ Cleaning of equipment

While waiting for the film to dry, all the processing equipment and workbench should be cleaned. It is much easier to clean and electrostatic treat the residual chemicals before they harden and agglomerate. While waiting for the film to be developed or dried, the equipment can be fully scrubbed. In particular, the residual wetting agent should be carefully removed from the developing tank and the spool. Because the chemical components contained in the wetting agent will weaken the development effect of the developer, and bubbles will be generated when stirring. Metal utensils should be dried quickly to prevent rust and pollution.

If the film cannot be developed with running water, a series of static water can be used instead: clean water with the same development temperature is injected into the developing tank, which is repeated for 6 times and soaked for 5 minutes each time.

◆ Chemical additives for cleaning.

Using cleaning agents (such as Kodak Haibo cleaning agent) can quickly wash the fixing solution off the film, which will shorten the washing time and save water. When Kodak Haibo cleaning agent is needed, it should be washed with clear water for 30 seconds after fixing, then the film should be put into the cleaning agent and stirred for 2 minutes, and finally washed with clear water for 5 minutes. If the image stability is very high or this cleaning agent should be used on photographic paper.

Removing excess diluted wetting solution from the film can speed up the drying process. After pushing the film, wet your fingers with diluted wetting solution, and then gently squeeze the film between the two hand grooves, preferably gently.

◆ Wetting agent

Immerse the washed film in a properly diluted wetting agent solution, such as KODAK PHOTOFLO solution, and gently stir for 30 seconds. Wetting agent can make the film dry easily and quickly, leaving no water stains.

Gently move your fingertips along both sides of the film to check whether the film is dry. If the film feels smooth and does not feel sticky, it is dry and can be cut. For 35 mm film, gently wipe it from the perforation by hand. It is easy to leave small water droplets here, and the film cannot be uncovered until the small water droplets on the perforation are completely dry.

Take both sides of the dry film and cut it into several small strips. In order to print samples, the length of the negative should be suitable for the length or width of the photographic paper used to print samples. For example, 36 35mm negatives should be cut into 6 sections with 6 negatives in each section. They can be printed on 8x 10 inch photographic paper, which is 20.3x25.4. Of course, this will definitely fill up the photographic paper.

Every film should be put in a special film bag or envelope, because some paper and chemical synthetic materials can't be used to preserve films, because they may contain chemicals that accelerate image degradation.

Film should be stored in a cool and dry place. High temperature and humidity will damage the effective life of black-and-white photos that have been strictly developed.

In order to facilitate operation and filing, cut the washed dry film into small strips, and then put the small strips into special film bags or envelopes.

If you are keen on photography, you will eventually accumulate enough negatives, and it is beneficial to establish a simple file for these negatives. You can easily find the negative you are looking for from the archives. A practical filing system is to give each film a number consisting of three groups of numbers. The first set of two digits indicates the year; A second set of one or more numbers represents the month; The third group of one or more digits indicates the shooting sequence in the same month, so the fourth volume shot in March of 198 1 should be marked as 8 1-3-4. For each specific negative and its printed photos, the film edge number should be added after the film number to show the difference. In the above example, the photo printed on the sixth film of this roll can be marked as 8 1-3-4-6.

The film number should be properly marked on the film bag or envelope, and not only the film roll number but also the film edge number should be marked on the back of the data sample. In this way, you can easily find the negative. If you need to archive the negatives according to the theme or shooting location, you can use the card index or binder to establish a simple coding system. Of course, data samples should also be filed or bound together in this order.

In order to make the service life of the film as long as possible, we should strictly follow the recommended cleaning process, store the film at normal room temperature (such as 60-80F or 16-27C), and store the film in a dry place with relative humidity below 60 to avoid the growth of mold and fungi. Because the silver image may be corroded by some sulfides, it is necessary to prevent the negative from contacting with hydrogen sulfide gas and coal gas.

After being properly filed, the negatives should be stored in a clean place without harmful substances. The use of binders is also one of the preservation methods of negatives and data samples.

Removing air bubbles: Air bubbles attached to film emulsion block the contact between developer and emulsion. When developing, tap the developing tank several times quickly to drive away bubbles.

Dark crescent mark: the mark is caused by reckless operation before development, which makes the film obviously fold.

Slice scratch: Dirt or coarse sand gets stuck in the film outlet of the camera's 35mm cassette, or fingers or sponges get stuck with dirt or coarse sand when removing excess wetting liquid, resulting in scratch.

◆ Deposition of stains and chemicals: This is usually caused by insufficient water washing or high concentration of wetting solution. Washing and drying again will improve this situation.

◆ Unformed stripes and spots: This is the water spots caused by accidentally wetting the small area emulsion with water again after drying, or it may be caused by water drops left on the film during drying. This usually happens in the absence of wetting agent.

◆ Small particles are embedded in the emulsion: this is caused by dirt or dust on the wet emulsion when it is dry. Washing with water again and hanging the membrane in a clean place to dry will improve this situation.

Completely transparent film: This is because fixer is mistaken for developer. First of all, it is poured into the developer tank, so the container should be clearly labeled to avoid confusion between developer and fixer.

Transparent film with only edge marks: although the film has been developed, it has not been exposed in the camera. You should check the camera loader and the camera shutter operation.

◆ Static electricity: Static electricity will cause a large area of marks on the film. When operating the film that has not been developed, it is necessary to avoid the film moving rapidly, such as fast film turning, because fast film turning will produce friction and static electricity. When unloading the film from the end of the film, you should also operate slowly, especially in a dry environment.

Irregular stains: On the film axis, the film bends away from the film path, making two adjacent films stick together, resulting in uneven washing and stains.

◆ The whole film is gray: the film is covered with a layer of gray fog, which may be caused by light leakage in the darkroom when loading the film.

Film that looks too dense:

This is either because the developer is not diluted enough, or the development time is too long, or the development temperature is too high, or the stirring is too large, or these factors are combined to lead to excessive development. It may also be caused by overexposure.

Low contrast: insufficient exposure; The contrast is too small: underdevelopment.

A film that looks small by comparison:

This is either because the developer is out of date, outdated or too thin, or the development time is too short, or the temperature is too low during washing, or the mixing is not enough, or these factors are combined to lead to insufficient development.

It may also be caused by underexposure.

Longitudinal stripes:

Because the liquid level of the solution in the developing tank is too low, the film reel can't be immersed in the chemical solution, and some films can't be fully developed or fixed.

Particle expiration:

It may be caused by severe overexposure or overexploitation. The sudden change of temperature in the washing process will also make the emulsion form a network similar to coarse particles.

Well-made data samples are good for photography. Using data samples, you can watch multiple pictures at the same time, which greatly facilitates the selection and archiving of photos. In addition, it can help you choose the best negative to enlarge and provide you with clues on how to enlarge each photo. Although it takes some time to make data samples, it can save you several times as much time as enlarging photos.

Data sample, also known as contact printing production, is a photo of a positive picture printed with a whole roll or part of negative film with normal tone. Each picture on the contact printed sample is the same size as the original negative. Remember, the density of each negative is not necessarily the same. Therefore, some pictures in the sample will be darker than others.

Put the frame used for contact printing on the bottom plate of the magnifying glass, turn on the switch of the bulb of the magnifying glass, turn off the indoor lighting, lift the head of the magnifying glass until it projects enough light to cover the whole frame, and adjust the focal length until the edge of the empty negative clip casts a clear shadow on the bottom plate and outlines the light receiving area.

It is necessary to adjust the height of the magnifying glass repeatedly and focus it many times to get a clear edge that is several inches beyond the frame. Pay attention to the distance between the head of the magnifying glass and the bottom plate and measure this distance. If there is a scale on the amplifier, it can also be read from it.

Whenever you make a data sample, you should adjust the magnifying glass in the same way. Every time the distance between the enlarger lens and the master is adjusted, the distance should be consistent, so that the photographic paper will automatically get the same illumination when exposed, and it is easier to determine the exposure conditions.

Mark the outline of the illumination area with the shadow of the bottom plate of the magnifying glass to form a contrast mask strip. When the light source of the power amplifier is turned off, these shielding strips can indicate the position where the contact printed frame should be placed, then turn off the light source of the power amplifier and turn on the indoor lighting.

Press the negative strip on the enlarged paper with the contact printing frame, so that the printing of the sample can be exposed.

◆ Preparation for contact printing

Contact print rack (hereinafter referred to as film rack) is a device for pressing negative strips on enlarged paper. Film photo frames sold in stores usually use hinges to connect giant glass or transparent plastic to a hard base and combine the two. Some types of film racks have a row of grooves or clips so that the film strips can be positioned accurately, while others do not. Both of these frames are used for 8* 10 inch (i.e. 20.3*25.4 cm) photographic paper.

Look at the film under the light, and gently blow off the dust or cloth attached to the film if necessary. When operating, hold the edge of the note to avoid leaving fingerprints on the screen. Check the transparent plate of the negative frame, and wipe off dust and fingerprints with a soft, clean and lint-free cloth. If the frame design is to put the negative film first and then the photographic paper, it should be arranged in the order required by the frame specification, and the emulsion of the negative film must face the photographic paper, otherwise the image on the proof will be upside down.

If the film strip is put in a transparent polyethylene film bag for photography, it is not necessary to take it out when making data samples. This kind of film bag can be used as long as the film frame can adapt to various film sizes. Making samples through film bags will make the film cleaner because you don't have to touch the film often.

When preparing to put the photo paper into the photo frame, turn off the indoor lighting, turn on the darkroom safety light, and take out a photo paper with normal contrast from the photo paper bag or carton. When operating, just touch the edge of the paper, carefully seal the container containing the photographic paper completely, and write the number of negative rolls on the back of the photographic paper with a ballpoint pen. Put the photographic paper in the photo frame so that its emulsion faces the emulsion of the negative film. The emulsion of photographic paper * looks brighter than the back of the paper under the safety light and is reflective. Lock the photo frame so that the negative and photo paper are pressed together.

If the use requirement of the film holder is to put the photographic paper first, and then put the negative film, then it must be installed under the illumination of safety lights from the beginning.

◆ Temporary film frame

If it is used by accident, you can temporarily prepare a picture frame, put a piece of photographic paper in the range marked by the shading strip of the negative film of the enlarger, with the emulsion facing up, and then cover it with a glass plate slightly larger than the photographic paper, so that the negative film and the photographic paper can be tightly pressed together. The sharp edges of the glass should be ground off with emery (silicon carbide) sandpaper, or the edges should be wrapped with adhesive tape to prevent cutting hands.

Before exposure (under the illumination of safety lights), check again whether the negatives are arranged neatly and the negatives are oriented correctly. If this step is not serious, the pictures on the proofs will be reversed because of the reverse direction of some negatives.

Check whether the focal length of the magnifying lens is suitable for all film sizes. The focal length is often marked on the fixed ring in front of the lens, as shown in the figure. If you don't know what kind of focal length lens to use, please refer to the magnifying glass manual.

The magnification of a lens with a longer focal length than the standard is smaller than that of the calibration lens at any height, and it is impossible to get a complete picture with a lens with a shorter focal length than the standard.

As mentioned above, adjust the height of the magnifying glass so that the head is close to the height required for making 8* 10 inch enlarged photos and similar data samples. Print the sample with enlarged paper and adjust the aperture of the lens to the aperture used for making 8* 10 inch enlarged photos. Adjust the timer so that the exposure time is the same as when enlarging the photo. By following these steps, you will usually make a data sample with an exposure at least close to the required exposure.

If you don't have enough darkroom experience to determine the correct exposure conditions for magnification, you can adjust the lens aperture to f/8 and set the exposure time to 10 second when printing the first sample. Since the experiment must start with certain exposure conditions, let's start here.

Make sure that the photo frame is facing up, put it in the lighting area, and then start exposure. After exposure, take out the photo paper from the photo frame.

◆ Cleaning of data samples

Clean the sample in strict accordance with the way of magnifying paper or printing paper.

After fixing for 30 seconds, you can turn on the light. Before turning on the light, check whether the bag or box containing the photographic paper is completely sealed.

If the whole sample is too dark, it is because of overexposure, so you can make a sample with appropriate exposure time.

The whole sample is too weak because of underexposure. When re-making, the exposure time can be extended and the correct exposure sample can be made.