Alan Marcus

The key to the kingdom is getting the exposure correct and repeatable and transferable. If we can do this, another photographer with a completely different lash-up , can duplicate your exposure results. Further we can write exposure directions that will operate universally. The problem is: The amount of light passes by an optical system is a variable based on focal length and the working diameter of the lens. Consider that there is a hodgepodge of different focal lengths and apertures, how could we tell some a photographer how to set their camera and yield a fateful image? Ratio to rescue: We use what we call a “focal ratio”, that’s an f-number for short. A ratio is dimensionless. This means we can set any lens set to the same f-number as any other lens as this method will deliver the same exposing energy regardless of the size of the lenses involved. Suppose a giant telescopic camera has a focal length of 1000 inches and an aperture diameter of 125 inches. We obtain the f-number by division. Thus 1000 ÷125 = 8. We say the f-number is f/8. Another photographer using a 100mm lens sets his aperture diameter to 12.5mm. The focal ratio of this lash-up is 100 ÷ 12.5 = 8. In other words f/8. This works so well we can ignore the dimensions involved and just say f/8. No need to know the aperture diameter to work the problem. All is figured out for you when you set your camera to f/8. The good news is: The f-number system takes the muddle away. Since the camera lens is a circular opening, the amount of light passed by the lens is created on the geometry of circles. Truism: If you multiply the diameter of any circle by 1.4 you calculate a revised circle that is twice as big in surface area. We use this scheme to calculate a series of circles, each with either twice or half the area. Since we are dealing we lenses we use this scheme to calculating a set of f-numbers that deliver twice or half the amount of light passed to film or digital chip. The series is: 1 – 1.4 – 2 – 2.8 – 4 – 5.6 – 8 -11 – 16 – 22 -32. Note: each number going right is its neighbor on the left multiplied by 1.4. Each number going left is its neighbor on the right divided by 1.4. Such a ratio set allows adjustment of a lens system that will yield a change in exposure based on 2x increments. Further the f-number system is universal, any lens set to the same f-number, passes about the same amount of light. This permits exposure settings that are unvarying between different all cameras.

You might try -- Procure a tiny keychain flashlight that will remain on without the need to hold a button. Place this illuminated flashlight inside the camera and close. Retire to a darkroom. Now begin to examine the camera's exterior. Rotate and look at all the seams. If you see light peaking through, you have discovered the source. You must allow sufficient time for your eyes to dark adapt to be certain that the housing and seams are OK. It takes a good 15 minutes or more for you eyes to adopt. If you are in a hurry, place an opaque eye patch over one eye. This is old trick of sailors, your covered eye will dark adapt. Best of luck!

I was Quality Control at DynaColor Aurora, Illinois photofinishing lab for K11 & K12 (many years ago).<BR><BR> OK to contact me<BR><BR> Alan Marcus

<p>Potable (drinkable) water is OK to use to mix the chemicals of the process. Purest use distilled or demineralized water to avoid disfiguring the film with solids dissolved the water used to mix the needed solution. For the most part, this is over kill. <br /> <br /> If you have any doubts that the developer or fixer (the two chief chemicals of the process) are good, you can easily run a test. Trim two snipping of film and place a small quantity of each in a cup. In a lighted room, immerse one snipping in the developer and the other in the fix. The slice in the developer will darken before your eyes in a matter of minutes. The sliver in fix enters opaque and quickly clears to become transparent. If these actions as described, likely both are OK. By the way, the time in the fix is twice the time it took for the film to become clear.<br /> <br /> Now let’s talk about clear film. Look at the edges of the frame. Do you see edge printing? All films have numbers, letters and symbols imprinted on the edges, outside the image area. These are applied using a “light” printer. This printer, projects the exposing light, exposing the edge of the film to data like the emulsion and batch number plus maker and frame number. If the film is clear but the edge printing is easly read, the film was OK and it likely developed OK. This condition proclaims the film was never exposed, perhaps operator error or camera mechanical failure. <br /> <br /> Total black film translates to “light stuck”. However it is possible, but not likely, that the developer was contaminated. <br /> <br /> Lastly, our good camera work, when spoiled by bad processing is a heartbreaker. If you have any doubts about the chemicals, replace so you are working with fresh stuff.</p>

<p>Photo films are somewhat forgiving should they be over or under exposed. We call this “latitude”. The black & white negative film generally tolerates, without degrading the final image, two stops over-exposure and one stop under exposure. When you deliberately re-rate 3200 ISO to 1600 ISO, you will likely over-expose the film by one f-stop. When you shoot 400 ISO film as if it were 800 ISO, you are deliberately under-exposing one f-stop. In both cases it is unlikely that any degradation will occur; these intentional re-ratings are within the confines of the latitude of negative films. </p> <p>As you know a negative film is not intended to be viewed; nobody looks at a negative and says “look at Aunt Sally, doesn’t she look good?” We print these negatives on paper and examine the prints. It is important to keep this in mind because during the print- making process we are literally taking the picture again. During this second exposure we substitute paper for film and we are taking a picture of the film. This second re-exposing onto paper affords us the opportunity to correct exposure errors made the first time around. This is why negative film has extended latitude. Because we generally view slide film directly, we do not have this opportunity; thus side film has greatly reduced latitude.</p> <p>If you intentionally or accidently under-expose and you wish for the lab to compensate, you ask them to “push process”. Conversely, film that has been over-exposed is adjusted by “pull processing. Tell the lab in plain words to push or pull and tell them the extent of the error in terms of “stops”. One stop is a doubling or halving of the correct exposure (2X error). Two stops is a 4X error, three stops is an 8X error.</p> <p>As to grain: All film images show “grain” or a granularly. Grain may not be noticeable if the prints are small, but enlargements will likely reveal the grain. Fast films, those above 400 ISO, inherently show more grain. The optimum grain structure is achieved when the film is exposed and developed as per the rated ISO. Under-exposure greatly induces a heightened grain. Over-exposed films also show intensified grain structure, however, over-exposure is better tolerated. </p>

<p>The light sensitive goodies that make up the image on film are held in place by a binder (glue) made from gelatin. This coat is called the emulsion. When we develop film, we submerge the film is a developer solution that is mainly water. When the water contacts the emulsion, the gelatin is caused to swell. This swelling allows the fluids of the developing process and the wash water to enter and do their job. After all the developing steps are completed, the film is allowed to dry.<br> <br> During drying, the emulsion shrinks back to normal size. Now water has what is called a surface tension that causes water remaining on the film’s surface to form beads (droplets). Should water beads remain on the film during drying, the area under the bead dries at a slower rate. Thus the area under the bead will have a different shrink rate than its surrounds. This causes a microscopic change in the thickness of the film in locations where these water beads linger. These show up as “water spots”, an irreversible surface blemish that will likely mar the finished image. To prevent this, we use a “wetting agent”. This is a detergent-like chemical that causes residual water to sheet and not bead. </p>

<p>I had the same kit; I used it in a closet darkroom in 1953. It got me started as a darkroom worker. Later in life I was Technical Manager at Eckerd Drugs. At Eckerd’s, headquartered in the Tamps Bay area of Florida, I built 7 giant photofinishing plants. Each was sized to develop and print 20.000 rolls of color film a day. These were in – Clearwater Florida, Miami Florida, Orlando Florida, Atlanta George, Dallas Texas, Houston Texas, and Charlotte North Carolina. The labs processed and printed for the 2,000 drug stores of the chain. The labs were sized to handle holiday volume. </p>

<p>Veneration fans from the hardware store are not generally light-proof. I have built many darkrooms and I always install venation. I use common wall fans from the big warehouse vendors. I use the smaller variety. I cut the entryway for the fan high up on the wall about a foot from the ceiling. Now most construction is drywall on both sides of 2 by 4 framing. When you cut this entry, you will see that the drywall on back side of the wall and that it will block the air flow. With a weight on a string or fixable probe, check the hollow space between the two drywall walls. You are checking to see have far down you can probe before encountering wood. Most walls will have a 2 by 4 at about the mid-point, others will be completely hollow inside. <br> <br> After discovering the location of a wood fire break (horizontal in the wall), on the other size an exit on the other side of the wall. This will be covered by an inexpensive air-condition vent placed lovers down. <br> <br /> After the holes are cut, using flat black spray paint, spry as best you can inside the wall. The idea is, the air can make a U-turn but light can’t. Best if the entry and exit holes are as far apart as possible. It doesn’t take a big fan, you can even use small ones from the computer store. I have used these, normally 12V DC, use a wall plug-in transform, the kind used to charge battery power tools. </p>

<p>In the 1930’s, the black & white films in common use were insensitive to red light. Thus films could be safely handled in darkrooms illuminated by a red filtered light bulb. Film development, in that era, was by “inspection”. The film was immersed in a developer solution under red light. Within seconds a faint image appeared and grew darker by the minute. Development was ended when the darkroom worker deemed the images had reached the desired strength. The developer solution is naturally “straw” colored. <br> <br> Development was ended by immersing the film in a mild acid bath akin to vinegar. The natural color of the stop bath is a pale yellow. Next the film was immersed in a “fix” bath. This fluid chemically rendered the images permanent. This solution is pale yellow.<br> <br> The film’s appearance under red only illumination is, to say the least, quite “ruddy”. Additionally the front side of the film is an opaque gray and the backside is opaque green or maroon. The opacity of the film is gradually removed by the fixer solution. <br> <br> I have never acknowledged that film, as it develops, appears yellow. A thought; many films of that era were only sensitive to blue light. These could be developed via yellow safelight. The darkroom illuminated by a yellow lamp is brighter; thus the darkroom is more comfortable. Additionally, the black & white films are printed using photo paper that is routinely handled under yellow safelight. It is possible that in some shops, blue only sensitive film was handled under the same yellow safelight designated for photo paper. </p>

<p> <br> Suppose you go to the kitchen sink to fetch a glass of water. You hold the empty glass under the faucet and turn on the valve for 1/125 of a second (0.008 seconds). Given your water pipe diameter of 5.6mm and the water pressure now, the glass is flawlessly (not under or over) filled. <br> <br> The factors involved in exposure are:<br> Scene brightness (water pressure now)<br> Shutter speed (period allowed for light or water to act)<br> ISO setting (sensitivity of imaging chip (size of container to be filled)<br> What is exposure compensation? Your camera or hand-held light meter reads out the combination of shutter speed and aperture setting for you to use given the ISO setting you chose. Your experience (sixth sense) whispers these settings will likely yield an under or over exposure. You intervene and input settings that override the instrumentation’s logic. You intentionally “+” or “-“ to modify the exposure.<br> We generally make exposure compensation changes using a unit called a stop. This is photographer’s jargon for a doubling or halving the exposing light energy. <br> We can make a 1 stop adjustment by changing the shutter speed; this allows more or less time for the exposing light to play on the imaging chip. This works because the chip accumulates light energy during the exposure. We multiply or divide the original shutter speed by 2. More time (+) from 1/125 of a second is 1/125 X 2 = 1/125 X 2/1 = 2/125 = 1/60 of a second. Conversely we divide by 2 = 1/250 of a second.<br> <br> We can also make a 1 stop adjustment by changing the lens aperture (f/number). To accomplish this, we increase or decrease the working diameter of the aperture so that the surface area of the lens is doubled or halved. In other words, it’s the surface area of the lens that determines how much light energy the lens will capture during the exposure. To do so, we either multiply or divide the current working diameter by 1.4. In your example this works out to 5.6 X 1.4 = f/8 (we round) or 5.6 ÷ 1.4 = f/4. The “f/” symbol is photo jargon for focal ratio. <br> <br> There are actually 4 ways to do this deed of exposure compensation. A third is to internally change the ISO by dividing or multiplying it by 2. <br> The fourth seems a bit impossible; we artificially alter scene brightness. We can do this if the scene is inside the studio. We bring to bear more or less lamps, be they flash or continuous. <br> Again exposure compensation is the deliberate changing of the one or a combination of the several of the 4 ingredients of the exposure. These are: Shutter Speed --- Aperture --- ISO --- scene brightness. For most vistas, scene brightness is not adjustable, so we talk about the “Exposure Triangle”. This is: 1. Shutter Speed 2. Aperture 3. ISO. It is the exposure triangle you need to study. </p>

<p>About the density unit:<br> In the early 1900’s Messieurs Hurter and Driffield started researching the relationship between exposure and development. They invented precision instruments to expose and measure how exposure caused film to blacken. This was before the calculator or computer, scientist used logarithmic notation as this method substituted addition for multiplication and subtraction for division. The slide rule is based on log manipulation. It was a natural to use log notation as the unit for the blackening of film.<br> The number 2 can be written many way such as two – or 2 or II. We can also use log notation base 10. The number two in this notation is 10^0.30. This reads – 2 =2 10 elevated to the .3 power. <br> I won’t go on with a lesson in logs but here are some key values that pertain to the blackening of film. <br> We omit the base which is 10 and only write the exponent. This is because once the base used is identified; we can omit it as now it is redundant.<br> 2 = 0.30 in log notation. Since an f/stop is represents a doubling or halving of the exposure, that one f/stop equals a 2X change in film blacking. This 2X change is written in logarithmic notation as 0.30.<br> Thus 1 f/stop = 0.30 density unit’s<br> 1/2 f/stop = 0.15 density unit’s<br> 1/3 f/stop = 0.10 density unit’s<br> 1/6 f/stop = 0.05 density unit’s<br> 2 f/stops = 0.60 density unit’s<br> 3 f/stops = 0.90 density unit’s <br> 4 f/stops = 1.20 density unit’s <br> Etc.<br> <br> Now Hurter and Driffeld constructed graphs of the blackening of film. When graphed in log notation, the shape of the graph is deemed elegant plus it was believed that human hearing and vison both plotted followed a logarithmic curve. Thus the decibel and the film density unit is today plotted as a log value. <br> <br> That’s the molasses, now the sulfur. The plot is called an H&D curve. In theory, a film should double in density with every f/stop exposure increase. In other words, the density of film should elevate 0.3 density units per f/stop increase. It can but – if black & white film is allowed to do this, the results are too contrasty. For this reason films are generally made less contrasty.<br> <br> We measure contrast by measuring the upward slope of the film as it blackens with exposure. If this slope angle should equal 45⁰, a 1 f/stop change = 0.3 density units. Another name for this slope is gamma. If the angle is 45⁰, the gamma is 1. This is two contrasty, we typically adjusts this angle to about 36⁰. Now36 ÷ 45 = 0.8, we call this gamma 0.8. This is slope of a typical black and white negative film. Such a film does not elevate 0.3 density units per 1 f/stop change. This less contrasty film elevates 0.3 X .8 = 0.24. In other words a typical black and white film elevates only 0.24 density units per f/stop increase in exposure. <br> <br> Now I know this stuff is difficulty, I can’t tell you a lot in a paragraph or two, so you can email me and ask questions. <br> <br> This stuff is what I call gobbledygook. </p>

<p>The learning curve is too steep! It's too late in the game to learn and keep the business going. Best you hire a knowledgeable person to run the studio and perhaps teach you how to do this stuff. </p>

<p>If a hand-held meter was used, and the filter factor of 2 (1 f-stop), was not applied, then have the lab push 3 f-stopss. If the thru-the-lens meter of the camera is being used, then ask the lab to push 2 f-stops.</p>

<p>Film, be it negative or slide, is viewed by tansmitted light. The light transverses the film once. The typical scale is 256:1 (8 f/stops) or better. Prints on paper are viewed by reflected light. Light from an adjacent lamp plays on the print. This light transverses the emulsion, hits a white reflective under coat and is reflected back towards the observer. This light transits the emulsion a second time. Thus we view film via one transit and prints via two transits. The scale of the print is about 64:1 (6 f/stops) if glossy and 32:1 (5 f/stops) if semi-glossy. Bottom line is, prints are more contrasty then the film.</p>

<p>Most likely, the film was not properly loaded on the film developing reel. Improper loading allows the to touch. This will prevent proper developing at every point of contact. Do procure a roll and practice loading the reel in the light - many times. The with eyes closed. Bet this will make a big difference!</p>

<p>Procure from the web some Farmers Reducer. This is a two part solution, bleach plus fixer. Farmers Reducer is used to lighten negatives that are over-exposed or over-developed. The bleach part is potassium ferricyanide. Sounds dangerous but the cyanide is too tightly bound to iron, and therefore has super low toxicity. It was, for years, the bleach of choice for color films and papers. It’s the best for what I am going to describe, however its replacement now in use in the C-41 color negative film process is EDTA. You could procure some C-41 film bleach for this task (not Blix which is EDTA plus fixer). After the beaching has completed, about 4 or 5 minutes, wash and dry. </p> <p> </p> <p>Make a batch of black & white prints in the darkroom. We are talking silver based gelatin prints. You know, the prints you develop, stop and then fix and wash. Immerse the finished black & white prints in the potassium ferricyanide solution (Farmers reducer part A). This step is performed in normal room light. The image on the paper will disappear. It’s not gone, just chemically changed back to a silver salt that is about the same shade as the print paper. </p> <p> </p> <p>Now for your science project: Demonstrate how black & white prints are developed in the darkroom. Only, you are going to do this in normal room light. Prepare four trays. Tray 1 is your usual paper developer. The other trays are for show, they can be stop, fix and water or all can be water with some yellow food dye added for show. </p> <p> </p> <p>For your demonstration, immerse a previously beached and washed paper print in the developer tray. Swish it about to agitate. You will see the black & white image reappear. As this is happening, tell your audience the science of film and paper developing. Look all this up and prepare a lecture. You can email me for the dialog. <br> <br> Best of luck!<br /></p>

<p>The typical roll of 35mm black & white film contains about 0.008 Troy Ounces of silver. Let’s say that about half that remains on the film and the remainder, 0.004 Troy Ounces is dissolved in the fixer. We process 100 rolls and recover all the fixer contained in the fixer. Our prize will be 0.004 X 100 = 0.4 Troy. We send this off to a refiner and find the yield is about 0.2 Troy Ounce of 99.9% silver. The going rate is $20. We can gain 0.2 X 20 = $4 US dollars minus shipping, minus refining charge. That’s your gain for 100 typical rolls. </p>

<p ><a name="00e6M2"></a>@ Eric Goldstein-- Thanks so much - I was Technical Manager for Eckerd Drugs, a Southeastern chain of drug stores. At its heyday, 2000 stores, now mostly absorbed by CVS. I built 7 giant photofinishing labs, each sized for 20,000 rolls of film developed and printed per day. I was forced to became knowledge in photo effluent and I was forced to pre-treat. We did silver recovery by every means possible and we recovered spent developers and reconstituted etc. Latter I was Technical Information Manager for Noritsu. Fixer and Bleach/fix is in my vanes, 55+ years and more. </p>

<p>Both human waste and photo waste have an oxygen demand. They both take on oxygen as they age. Eventually this results in the waste becoming inert. The waste treatment plant must aerate to cause the plant’s effluent to go to completion. The plant must be sized to handle the load of the community. A big photo lab or food processing plant or industry discharging waste with oxygen demand could challenge the plant’s capacity. This is especially true in summer. Warm water has less ability to hold oxygen. If the plant is overwhelmed, they can’t stockpile the waste, so they must discharge it. If the effluent continues to take on oxygen it enters nearby waterways and competes with the aquatic life for oxygen. A fish kill or algae bloom results. Big photo labs that discharge lots of photo waste may need to pretreat their effluent to reduce oxygen demand. </p>

<p>That’s a good question!<br> There are two fixer chemicals, both do the same job. The original fixer is sodium thiosulfate which is customarily replaced by ammonium thiosulfate. <br> <br> Photo films and papers are coated with unflavored and highly purified gelatin. This is the binder (glue) used to affix the light sensitive material to the film or paper base. Gelatin is chosen because it is transparent, flexible, and preamble. The gelatin coat swells when wet, this allows the chemicals of the process to infuse and reach the light sensitive chemicals. When the material dries, is shrinks back to it original size. <br> <br> The light sensitive goodies are salts of silver. These resemble table salt, however they smaller crystals and slightly off white. When exposed to light, they are rendered developable. The developer is able to distinguish the differences between exposed and none-exposed crystals. The developer reduces (splits) the exposed silver salts into its two component parts. The silver part remains trapped in the gelatin. This is metallic silver and it is opaque. This is the metal that makes up the photographic image. The other component is a halogen. The liberated halogen is dissolved away by the developer which is mainly water. Halogen is Swedish for “salt maker”. We use thee members of the halogen family of elements in photography. These are bromine, chlorine and iodide.<br> <br> After the developer has done its job, an image is seen. This image is comprised of metallic silver. Surrounding the metallic silver image will be silver salt crystals that were not exposed and therefore did not develop. It is necessary that these be removed from the gelatin. If they were to remain, in time, they self-reduce and liberate metallic silver. This is also opaque and it blends in with the desired image. The result is, the entire image will darken. We say it faded. <br> <br> Fixer to the rescue: We immerse the film or paper in a fixer solution. This is a solvent for silver salts but not a solvent for silver. The unexposed and thus un-developed silver salts are washed away and dissolve into the fixer which is mainly water. The image comprised of silver remains. We than wash the film or paper to purge it of residual chemicals.<br> <br> How dangerous is the chemicals of the photo process? The answer is – they are pretty benign. <br> Test after test has shown they can safely go in the sewer system. OK – what are the ramification? The spent fixer contains silver in solution. Some forms of silver are toxic. The authorities are afraid that the fixer will disrupt the biological action of the sewer treatment plant. This likely won’t happen because as the fixer travels in the sewer line, sulfur is comes out of solution. The sulfur and the silver combine to form silver sulfide and inert chemical. Why photo waste is considered toxic? Again some forms of silver are toxic and when a municipally tests photo effluent they use nitric acid to test. This liberates the silver and the outcome of the test is positive. The municipality must dispose of solids generated by the waste treatment plant. If it test positive for silver, its value as a fertilizer is reduced.<br> <br> Now the real harm: Fixer is the same chemical used in tropical fish hobbies. This is the chemical they add to purge city water of choline. The municipal sewer must treat discharged effluent with chlorine to render it safe from bacteria. If lots of fixer is in the sewer, they must use double or triple the amount of chlorine. This is costly. <br> <br> Is photo chemical effluent benign? The authorizes are not worried about this unless the source is a big industrial photo lab. Hobbies and school darkrooms will not impact the municipal sewer system or harm the environment. However, it is always better to be good neighbors and avoid putting anything down the drain that has the potential to harm. <br> <br> I was a registered environmental engineer with a specialty in photographic waste. </p>

<p >Sorry you had this bad experience!</p> <p >There is a problem with your darkroom technique but I know beyond any doubt that the foremost problem is related to your camera.</p> <p >The image of the film you posted shows blank frames however the edge print is bold / readable. Film is imprinted with edge printing applied by the manufacturer by exposing the edges. We are talking frame numbers, barcode, emulsion number, batch number etc. Edge printing develops up along with your images, if any. The fact that we can read the edge printing is positive proof that the developer did its job. This means that the roll was not exposed in the camera or the exposure was too weak to record. Maybe the advance mechanism failed or the shutter failed or your setting yielded a super severe under-exposure. </p> <p > </p> <p >That being said, the posed image reveals film that was overdeveloped and /or fogged. The developed film is too dark, and this indicates improper handling. Maybe the darkroom area was not it total darkness. Also, the film has high density streaks that radiate from the sprocket holes inward. Likely the cause is a combination of gross over agitation and over development. We agitate to insure that all areas of the film receive equal and even developing. As film develops, areas where the exposure is great prompt lots of development action. The absorbed developer in these areas quickly exhaust, so we agitate to flush out spent developer and infuse fresh. You aggressively agitated and this induced turbulence at the sprocket holes. This turbulence caused streaking overdevelopment. Best to agitate continuously for the first 30 seconds, and then 5 seconds of agitation every 30 seconds. </p> <p > </p> <p >You can use a water-bath for the stop bath however, the stop is a dilute solution of acetic acid. This is another name for vinegar. OK to make your own by adding a teaspoon of table vinegar to a liter (quart) of tap water. </p>

<p>The camera settings can be made the old fashion way using a “guide number”. With few exceptions, the flash manufacturer publishes a table of “guide numbers”. If not available you can test and generate your own table. <br /> <br /> The “guide number” is published based on the ISO of the film or digital setting. For the moment let’s work with a “guide number of 110. <br /> <br /> To use: Compose the picture and focus; consult the camera’s distance scale or estimate flash to subject distance. Let’s say it’s 10 feet. We divide the guide number by the distance thus: 110 ÷ 10 = 11. We manually set the camera’s aperture at f/11. Suppose the flash to subject distance for next shot is 15 feet. The math is 110 ÷ 15 = 7.3 -- we set the f/number to the closest value which is f/8. <br /> <br /> The published guide number system will have two sets of numbers, one for folks that measure distance in meters and one for feet. The numbers are different but the method of application is the same. Additionally the guide number table will list different guide numbers for different ISO films or settings. <br /> <br /> If unable to find the published guide numbers: Setup the camera and a test subject in a typical picture taking situation. Place the principle subject at 10 feet distance. Shoot a test sequence at each f/number setting. Inspect the resulting images for best exposure. Say the ISO setting (or film speed) is 100 ISO and the best exposure is f/11. Now multiply distance X f/number -- thus 11 X 10 = 110. This will be the guide number for your flash unit based on this setup.<br /> <br /> As to Shutter speed: The electronic flash outputs a super-fast blitz of light. Your shutter speed setting, so long as it is synchronized with your camera’s shutter, is moot. In other words the shutter speed will not impact exposure. We set the shutter speed based on the camera setting that will allow flash synchronization.</p>

<p>The light fogging is too gross to have happened in the camera. Maybe it occurred during loading or unloading. Most likely this happened at the lab. Best to test your camera with a surficial roll, you can use a high speed black & white. Which that test roll is at the lab, procure a keychain flashlight that will remain on. Place this light, turned on, inside the camera. Now take yourself and the camera into a totally darkened room. Know that if light leaked into the camera, it will also leak out. Sit in this darkened room for 15 to 20 minutes. It takes that long for your eyes to adapt to a dark environment. All the while your eyes gain in ISO. All the while, examine the camera from all angles. If there is a light leak, it will be at the margins of movable joints. Again it takes time to dark adapt, maybe you will see some light leaking out. </p>

<p>As you know, photographic film and paper consists of light sensitive crystals comprised of silver and a halogen. Halogen is Swedish for salt maker. Thee members of the halogen family are used in photography. These are, listed in order of their sensitivity to light, bromine, chlorine, and iodine. <br /> <br /> Let’s take about a medium speed emulsion. We start with a 10% solution of silver nitrate. This is added to a vat of gelatin containing potassium chloride. As these ingredients blend, minute crystals of silver chloride form. This mix is called an emulsion. Actually it is a colloidal suspension and not an emulsion. The term emulsion is wrong but it’s too late to change this term, it’s use has been with us too long. <br /> <br /> The goodies in the vat are not very light sensitive. The stuff must “ripen”. The batch is heated and held at about 90⁰F (32⁰C). Super tiny crystals dissolved and re-deposit on larger crystals. This process spawns larger and more uniform crystals. Gelatin is made from animal bones; it is a complex mix of chemicals. The gelatin contains natural Impurities like sulfur plus other trace amounts of chemical impurities are added. A reaction takes place, the sensitivity to light increases. After the ripening behavior is complete, the mix is cooled and a jelly forms. <br /> <br /> The jelled emulsion is shredded and washed. The emulsion is then heated and remelted. Now it is coated onto film or paper. Chemicals are added to harden the gelation plus dyes are added. These dyes force the silver crystals which are naturally only sensitive to violet and blue, to become sensitive to red and green as well. <br /> <br /> It’s the impurities and the dye and other special additions that make the final product. During the ripening sage, the size of the final crystals is determined. Now a bigger crystal has a better chance of being hit by a photon during exposure. Thus the bigger the crystals, the faster the film. Impurities can change the shape of the crystals. A modern “T” grain film (Tabular) has crystals that are shaped like flat stepping stones. The idea is a bigger crystal with less mass. These are orientated so their flat size faces the lens. They are big but have lower mass so they make fast fine grain film.<br /> <br /> A fine grained developer contains “silver solvents”. The idea is to dissolve away some of the sliver that forms during the development process. So fine grain film contains silver crystals that are smaller or have less mass. Grain is a clumping together of many individual flakes of metallic silver.</p>

<p>Most film developing formulas and methods suggest 20⁰C. I once research this and found that it was chosen because that was/is an average room temperature in Europe. That being said, the most important idea to express is, try to keep all the fluids at or near the same temperature. This is true because film contains multiple coats on the film base. Each coat will likely have a different coefficient of expansion. In other words, the emulsion swells when wet and likely all layers will not expand at the same rate. The swelling is necessary as it allows fluids to better infuse and percolate about. As the film dries, the emulsion shrinks back to almost its original thickness.<br> <br> Now developing time in solution is a variable. Temperature is key as is chemical strength. Most developer formulas come with time/temperature charts. No harm if the fluids are a few degrees above or below 20⁰C. Follow the time /temperature chart and try to keep all fluids nearly the same. <br> <br> I normally, for black & white films and papers, measure the temperature of the running water and work all fluids at that temperature. This is easy if you keep all the bottles and the film developing tank in a pan filled with running tap water. If this is impractical, place ice in the water tray and adjust all fluids to the same temperature. <br> <br> The 20⁰C for the fluids keeps the developing time within reason. The idea to keep all fluids the same temperature avoids reticulation. This is a condition whereby the emulsion appears as if it has shattered like a hit on automobile safety windscreen. Reticulation is caused by rapid changes in temperature as the film moves from solution to solution. Films that exhibit lots of grain can be traced to incipit reticulation, an early, not too noticeable stage of reticulation. </p>