Different pieces of literature and many friends that shoot black and white have recommended always using 1/2 film speed, eg: Delta 400 at 200, etc. When asked why, the response is "I'm not sure, but I was told it makes better negs". Their are some people that always leave an orange filter on the camera. I understand the theory of both procedures, however should this be the norm on all photographs?

Thanks, Bob

-- Bob Passage (bgpassage@earthlink.net), September 01, 1999

Answers

Hi Bob

Doing anything without understanding in B&W photography is not wise. Much of the appeal of B&W photography is the ability to visualize the image and control the outcome to a certain extent.

Films have an intrinsic degree of sensitivity to light that is designated by the ASA. Routinely over-exposing a film by 1 stop (i.e. "pulling" or exposing at half speed) can be done if you compensate with your development, but it's not what that particular film was necessarily designed to do. Over-exposing B&W negatives is better than under-exposing them since you don't lose as much detail. However, the "best" exposure is the one that helps you capture the image as you visualized it. A given film will be most responsive to this type of maneuver or Zone system if it is used at or near it's designated ASA. It is within this range of exposures for which the film was intended. Personally, I prefer to set my meter at the films ASA, then apply my own simplified version of the Zone system.

As far as filters, there's a great thread from a few days ago with wonderful explanations from August and several others. Filters are tools only and I doubt you would get any benefit from leaving one type on routinely unless you photograph one specific type of situation exclusively.

Asher

-- Asher (schachter@a1.tch.harvard.edu), September 01, 1999.

Asher is essentially correct. The ISO number for your film is a starting point. The effective exposure index EI must be determined by you, based on your camera, developer, processing procedures, enlarger, and what you want in a negative to get the print you want. No, cutting the ISO in half isn't a good general idea. Start with the ISO number, develop it as recommended by the maker in a couple of different developers, and make prints. Then, if results aren't what you want, change ONE thing at a time - EI, developing time, etc. If you understand the theory behind the changes, you won't have to make too many tests until you get the negative and print you want. But that can only happen after you calibrate your system yourself.

-- Richard Newman (rnewman@snip.net), September 01, 1999.

bob, here's a wonderful article on finding out your personal EI .

www.wenet.net/~halfhill/speed1.html

have fun.

-- hoko hoko (photoq@hotmail.com), September 02, 1999.

Bob there's nothing I can add to the above answers about film speed but I can garauntee that the vast majority of the best photographs of all time were taken without an orange filter.

-- Andy Laycock (agl@intergate.bc.ca), September 03, 1999.

Finding the proper film speed for your equipment(lens/shutter/meter) are what help determine how the shadows will be represented on the film. Some photographers use the film at the manufacturers recommended film speed because they 1) don't know any better or 2) have determined through testing that it is the correct film speed for their equipment and style. But most photographers eventually find that they must calibrate a film speed that will render their shadows correctly on the film they use. I shoot Tri-X sheet film, rated by the manufacturer at ISO 320, down at ISO 160 because that is where my shadows have the correct zone 3 placement. That is the film speed which gives me a deep shadow which is the last black with good detail in the print. Any faster and the shadows are to deep rendering only blacks with no detail. That is why you see photographers shoot their film at less than the manufacturers ISO's. Then you must determine which development time you are going to use for rendering your highlights correctly. But that is a different thread. E-me and we'll discuss it. As for an orange filter, all that does is shorten film speed by decreasing the amount of light reaching the film thereby underexposing it unless they are compensating for the underexposure by increasing their exposure times. Run a simple film speed test and find out what it should be. That's the path to good prints or chromes. James

-- james (james_mickelson@hotmail.com), September 03, 1999.

Bob, these are great answers, but I would add that it is important to understand that your equipment is all part of the equation. Your meter may read high or low, your shutter may be slow at one or more speeds, your metering technique may be incorrect, your processing and printing techniques may be faulty - all these and more can cause you to think that you have to shoot at some fraction of the film's rated speed. It's a very useful exercise to periodically test your own equipment and adjust ASA for the above conditions. But recognize what is happening - it isn't that the film is mislabeled or the manufacturer doesn't know what it's doing. It's your equipment that you must adjust for, your own technique.

-- August Depner (apdepner@uswest.net), September 04, 1999.