Tag Archives: Film speed

Q & A: How to clean shutter?

Yes, I know the rule is never to lubricate shutter blades, and I haven’t. I acquired an old Zeiss Ikonta which had that common ailment, sticky slow shutter speeds on a Prontor-SV shutter. So I tipped in a small amount of lighter fuel, which normally does the trick, exercising the shutter a few dozen times, and it seemed to free up, with 1s sounding like 1 second, and so on. It seemed perfect. But after an hour or so, the shutter just stuck completely, and a few more drops of lighter fuel freed it up. Then the cycle repeats. I’m wondering if the lighter fuel is reaching the blades and acting as a lubricant, and when it dries out, the blades are causing the shutter to stick, rather than any gunge in the shutter assembly itself. I’m not sure.

I know there’s a tip elsewhere on this forum that if it’s absolutely necessary, shutter blades can be gently lubricated by a finger smeared lightly in fine graphite pencil, but I’m hesitant about this in case I’m on the wrong lines entirely.

I’d be grateful for any pointers. This little Ikonta 521 is otherwise a perfect little peach and I’m getting restless now about putting a roll of film through it.




What you’re experiencing is very common. Most of us have come across it an one time or another. What has happened is that the original sticky slow speeds were caused by dirt/dried oil in the slow speed escapement train. When you used the lighter fuel you freed this, but the old oil on it has washed down and distributed itself on the shutter blades. When you add more lighter fuel you dilute this oil enough to break down its surface tension but it reforms as soon as the lighter fuel dries out. It’s got to be washed out completely – adding graphite or anything else will only form a sticky paste.

You don’t say how far you disassembled the shutter, but it’s best if you take it off the camera (usually a screwed ring round the shutter housing inside the camera), remove both the front and rear lens elements and take off the speed control plate so that you can see all the mechanism.

Then there are two ways of getting it clean, the long way, which purists will tell you is the ‘proper’ way, and the short way which, for me, works about 90% of the time. Try the short way first.

Lay the shutter in a shallow plastic tray, something like a ‘chinese take-away’ box, keep flooding it with lighter fuel and working it while it’s wet to try to wash all the old oil out. Keep doing this until the shutter works when it’s dried out.

Lighter fuel in small cans is quite expensive but it’s only refined naptha. If you can buy ‘commercial grade’ naptha it’s cheap enough to cover the shutter with it and swirl thigs around. On really sticky shutters, as an alternative to naptha or lighter fuel, I have used an aerosol of carburettor/injector cleaner from my local auto store. It’s a very powerful degreaser, two floodings are usually enough to get the shutter really clean, but be careful how you use it. ALWAYS use it in the open or in a ventilated outhouse because the fumes are nasty things to breathe. Second, don’t use it if there are any plastic bits attached to the shutter because some of these injector cleaners will dissolve many plastics.

With regard to operating the shutter while it’s still wet with cleaner, the shutter should work in ‘B’ mode with the speed plate off, or you can put the plate back on and just hold it in position while you work the other speeds. A tip for replacing the speed plate – put it on in approximately the correct position then give it a gentle turn anticlockwise till you hear a click as the pins drop into their respective slots.

If this is the first time you’ve been inside a leaf shutter have a look at Daniel Mitchel’s site
and scroll down the index on the left till you come to ‘shutters’ and have a look at ‘Prontor SVS’, which is an updated version of your Prontor SV.

Daniel gives a detailed, illustrated, blow-by-blow account of stripping a Prontor completely to pieces for cleaning (the ‘long way’).


Beginner’s guide to photographic films

The vast majority of photographer’s nowadays use digital cameras due to the ease of use, instant preview gratification, straight forward storage, the ease of making many copies and sharing, and many other reasons. But even so, many remain faithful to film and swear by it mainly because of its high quality and dynamic range, nostalgic and true feeling, as well as lower equipment cost.

With film, it all comes down to an emulsion with silver components that act as a coat on which images are recorded, and it has made significant improvements in quality and characteristics since the early days when it was used.

Emulsion is a light-sensitive coating on photographic paper or film that consists of fine grains of silver halide salts (suspended in gelatin) with variable crystal sizes that determine the sensitivity, contrast and resolution of the film. When film emulsion is exposed to light it forms an invisible image, from which a visible one can later be extracted through a series of chemical processes during development.

The size, shape and closeness in position these silver halide salts have directly affects the size of grain and film sensitivity to light, from fine grain (less sensitive to light) to coarse grain (more sensitive to light).

Film mainly falls into one of two categories: color film and black and white film. With color film, the image is more like what the eye sees and relates to in reality, but one must be careful of major color cast and hue variations. With black and white film, the image is more of an interpretation of reality. It requires more thought when it comes to light and image components (such as forms, shapes, texture … etc), but is more forgiving in terms of exposure.

Once a film is processed, the image can be printed on chemically coated paper, as well as scanned for further digital manipulation and sharing online, then digitally stored.

Film Size

The most popular color as well as black and white film size is the 35mm film, which is considered full frame. Cameras usually create 24 x 36mm frames on a long roll of film, with enough length for 12, 24 or 36 frames.

It is also known as 135 film which is a term Kodak introduced, and comes as rolls packed in light-tight metal cassettes which allows for loading in day light. 35mm film can be processed in all labs everywhere, and 35mm cameras, lenses and equipment are the most available of all film camera types.

A larger film size is the 120 medium format film and comes backed in opaque paper and tightly rolled on a plastic spool. 220 film is the same size as 120, but lacks the paper backing allowing more film to fit on the spool. The lack of protection means that most medium format cameras are not equipped to handle 220..

Medium format film is shot in many aspect ratios depending on the camera or frame insert used, with the most popular being 6×4.5cm, 6x6cm, and 6x7cm formats.

6×4.5cm is a rectangular format. The actual image size of this format is about 56 x 42 mm, with 16 exposures per 120 roll.

The slightly larger 6x6cm format is a square format. The final image can later be cropped to a more preferred format (with a vertical or horizontal orientation). Actual image size of this format is 56 x 56 mm, with 12 exposures per 120 film roll.

Larger format cameras exist, including 6x7cm, 6x9cm, 6x12cm and even 6x17cm. These cameras are less common, but can produce stunning images.

Sheet film is typically large film format that comes in separate sheets instead of rolls. These sheets are packed in boxes as 10, 25, or 50 sheets per box. Most common sheet film sizes are 4×5 inches and 8×10 inches, though other sizes can also be found.

Sheet films are fitted into holders and inserted into the camera so that exposures can be made. Each sheet has an edge-notching on one side which helps the photographer determine which direction the film should be at when inserting and changing in the dark.

When the exposure is made, the holder along with the film are removed from the camera, and another new sheet is inserted for the next shot.

Film Sensitivity to Colors

A film’s sensitivity to colors is set during the manufacturing process, and it differs between color film and black and white (monochromatic) film.

In black and white film, the emulsion is usually sensitized to all colors of the visible spectrum and even to shorter ultra-violet (UV) wavelengths as well. This, of course, is different from what the human eye is naturally accustomed to and sees.

In color film, emulsion is made in multiple layers stacked up one on top of the other so that part is sensitive to blue only, part is sensitive to blue and green, and part is primarily sensitive to red color. Most manufactured color films are set to give an accurate color balance under day light shooting.

Film Speed

Film speed is usually expressed in the US-based ASA rating or the European-based DIN rating. For all intents and purposes, ASA is identical to ISO rating. Film speed serves the exact same purpose that the ISO does in digital photography.

The higher the film speed (commonly known as fast film), the more sensitive to light it is and the coarser image grain will be. The lower the film speed is (commonly known as slow film), the less sensitive to light it is and the finer image grain will be.

Grain in film photography is the equivalent to noise in digital photography, though grain is sometimes considered to have an aesthetic appeal and sometimes even sought for its interesting visual effect.

In general, film grain affects the sharpness and fine details of the image with higher grain sometimes breaking continuous tonal gradation and edge contrast.

The main challenge for film manufacturers is increasing film speed thus making it more sensitive to light, without increasing the graininess and decreasing the sharpness of the image, so as to preserve minute image details and local contrast.

Professional and Non-Professional Film

The main difference between professional and non-professional film is that professional film is designed to give its optimum performance upon leaving the factory and should be refrigerated immediately until used. It should also be processed as soon as being exposed.

Non-professional, or amateur, film on the other hand is designed in such a way to allow for extra storage time while being kept at camera shops and at home or the studio until exposed. It can be stored at room temperature, and doesn’t have to be processed as soon as being exposed.

Professional film is slightly more expensive than non-professional film for the same film speed and size. Non-professional film is by no means inferior to professional film. Each type has its own uses, purposes, and audience with non-professional film being used by professionals all the time.

In each case, some of the most common causes of damage to film are humidity, storage in bright light or exposure to chemical fumes. Color film and fast film are particularly more prone to damage than black and white film and slow film. In general, if you keep the film sealed in the fridge, it should be fine even past its expiration date sometimes.

Keep in mind that film once taken out of the fridge should warm up to room temperature. Un-packaging the film and shooting too soon might cause condensation to form and ruin the film. Also when shooting outdoors in cold weather, make sure you keep the film warm in your pocket until it is time to load and shoot.

If film is not processed straight after exposure make sure you keep it in a dry, cool, dark place away from humidity and bright light, such as in a closet. If you want to put it back in the fridge, make sure you seal it in an air-tight box or a zip foil bag with a packet of silica gel.


Digital photography has taken the world by storm lately, and more and more photographers have been switching to the new trend, some of whom may never look back.

To others however, film remains the real deal. Every medium has its own strengths and weaknesses. In the end, it is always up to the individual and their taste to decide which way to go. It doesn’t really have to be one way or the other, though. Whether you like film or you like digital, you can still experiment and play with both.


Source: http://photo.tutsplus.com/articles/hardware/a-complete-beginners-guide-to-photographic-film/

Exposure Index

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Exposure IndexThis is a featured page

Exposure index (EI) is the measure of the amount of exposure received by the image receptor (IR). It is dependent on mAs, total detector area irradiated, and beam attenuation. The exposure index is indicative of the image quality. Equipment manufacturers provide a recommended EI range for optimal image quality (Bontrager & Lampignano, 2005, p. 52).EI in digital radiography can be compared to film speed and blackening in film-screen. When film was used, the accuracy of the exposure was obvious based on the appearance of the image. Digital systems post-process images and display adequate contrast and brightness at a much wider range. Therefore, adequate exposure can only be assessed through image noise or burn-out. Secondary workstations such as those used by technologists for image review, are often of lower resolution and brightness than those used for diagnosis. Because of this, it is often difficult to assess whether an image is noisy or not. The exposure index is meant to be an indication of whether the noise levels are acceptable (AAPM, 2009).

Errors in the calculation can occur resulting in an inaccurate EI. This can arise when the software fails in determining which part of the image is the patient anatomy, for example, in the presence of gonadal shielding or prosthesis. EI cannot be solely relied on, therefore the technologist must remain critical of the appearance of the image and the accuracy of the EI (AAPM, 2009).

EI is derived from the mean detector entrance exposure which is derived from the mean pixel value of the image. Most systems use a histogram analysis in order to calculate the mean pixel value (Neitzel, 2004, p. S231).


This is a histogram created from an AP pelvis radiograph. The x-axis represents the pixel value while the y-axis represents the number of pixels with that value. The mean pixel value here is 104.381.

Although EI is always derived from the IR exposure, equipment manufacturers calculate the numeric value differently, resulting in different ranges and definitions (Carlton & Adler, 2006, p. 367; Neitzel, 2004, p. S231). Also, there is variation between units purchased from the same manufacturer based on different IRs and software (Carlton & Adler, 2006, p. 367). Different IRs have different detective quantum efficiency (DQE). A high DQE results in lower noise levels (AAPM, 2009, p. 3). Therefore, all systems have a different index and are difficult to compare across systems.

Fuji CR

Fuji uses a sensitivity number (S) that is related to the amount of amplification required by the photomultiplier tube to adjust the digital image. S is inversely proportional to exposure. Properly exposed images should have an S between 150-250 (Carlton & Adler, 2006, p. 367).

Kodak CR

Kodak uses the term Exposure Index, which is directly proportional to exposure. Properly exposed images should have an EI between 1,800-2,200 (Carlton & Adler, 2006, p. 367). A change of 300 in the EI indicates a change of a factor of 2 in the exposure to the IR.

Agfa CR

Agfa uses log median exposure (LgM). This system compares the exposure level of the image to a baseline established for the department. Since it is based on a log system, an increase of 0.3 means the dose was doubled (Carlton & Adler, 2006, p. 367). An optimal exposure lies between 1.9 and 2.5.

Philips DR

Philips uses an EI that is inversely proportional to exposure. This index is represented in bigger discrete steps (eg., 100, 125, 160, 200, 250, 320, 400, 500, etc). Each step requires a 25% change in exposure to occur (AAPM, 2009). An optimal exposure lies between 200 and 800.

Imaging Dynamics DR

Imaging Dynamics uses f#. The f# compares the exposure to an established target exposure. Negative values represent underexposure, while positive values indicate overexposure (AAPM, 2009).

Canon DR

Canon uses a reached exposure value (REX). REX is a function of the brightness and contrast as selected by the operator (AAPM, 2009).


GE uses the detector exposure index (DEI) which compares the detector exposure to the expected exposure value (AAPM, 2009).


Siemens uses an Exposure Index (EXI). EXI is calculated by dividing the field into a 3×3 matrix and assessing only the central segment, and is based on the selected organ program. EXI is directly proportional to dose. Doubling dose doubles the EXI. EXI depends on organ program, whether manual exposure or AEC was used, and the measuring field (AAPM, 2009).

Future Developments

In 2008, the International Electrotechnical Commission (IEC) developed and published the International Standard IEC 62494-1 on the definition and scaling of the exposure index for digital radiography. According to the standard the EI shall be proportional to the exposure (air kerma) and shall be scaled as EI = 100 * X, where X is the air kerma at the detector, at the calibration beam quality. It is expected that this standard definition will be implemented in future digital radiography systems.

The American Association of Physicists in Medicine (2009), published a document in July, 2009 with the purpose of identifying a standard index which reflects the adequacy of the exposure received by the IR.


American Association of Physicists in Medicine. (2009). An Exposure Indicator for Digital Radiography. Retrieved from http://www.aapm.org/pubs/reports/rpt_116.pdf

Bontrager, K. L., & Lampignano, J. P. (2005). Textbook of radiographic positioning and related anatomy (6th ed.). Elsevier Science.

Carlton, R. R. & Adler, A. M. (2005). Principles of radiographic imaging: An art and a science. Delmar Learning.

International Electrotechnical Commission (2008). IEC 62494-1 ed. 1 Medical electrical equipment – Exposure index of digital x-ray imaging systems – Part 1: Definitions and requirements for general radiography

Neitzel, U. (2004). Management of pediatric radiation dose using Philips digital radiography. Pediatric Radiology, 34(Suppl 3), S227-S233.