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| Advanced Questions by Chuck McKern
Send us your questions for either the Beginner or Advanced columns by clicking HERE. Please include as much detail about the technique, camera, lens, or film as you can so Chuck can answer your questions. I have never quite understood the technical aspects of pushing film. How is it that a film designed for a particular ISO rating can be "pushed" to deal with different lighting situations? For example, what exactly is happening when I push Provia 400 to 800? I understand that a film's ISO rating corresponds to its light sensitivity. So, how is it that a film can be "modified" to work in low-light situations? Why does the grain increase when pushing, if the film is designed to be a fine grain film? I hope I am making sense. I understand the cause and effect, but I am curious to know why. Thanks for your help. Pushing film is a technique to let you rate a film at a higher ISO than the manufacturer rated it for. This can allow you to squeeze out some extra film speed in low light conditions. This doesn't mean you just set the ISO higher and all is good. By setting a film speed higher, you are making the camera think that it has a faster film than it really does. This will cause the film to be underexposed by the same amount. For example, if you are using 400 ISO film and you rate it at 800 (one stop faster), you will underexpose the film by one stop. For the image to look properly exposed, you have to take steps to correct for this. With slides the film will have to over developed to compensate. It is the combination of the two that we call pushing. Because of the altered development process, it is important that you push the whole roll and not just one or two frames. You can't switch part way and get everything to develop properly. The process of overdeveloping causes the edges of the silver in the film to become more defined and rougher than intended. In the final image this appears as more pronounced grain. Pushing can also be creatively to intentionally increase grain for added effect in a photograph. To see some examples of extreme push processing check out our review of Fuji Provia 400F where we pushed this ISO 400 film to ISO 3200 ! There is another related technique called pulling. This is the exact opposite of pushing. You rate a film at an ISO lower than its recommended rating causing the film to be overexposed. The film is then underdeveloped to compensate which tends to have tightening effect on the film grain. This discussion applies only to slide film. One of the advantages of negative film is its increased exposure latitude. That means you can over or underexpose a negative by a stop or more and still get a quality print. How much latitude you have to over or under expose any film will vary. Each film manufacturer publishes technical bulletins (usually available on their Web sites) with specific information on how many stops over/under exposure are possible before there's noticeable image degradation. I am getting back in to wedding & wildlife photography after many years. What would be some real good quality printers for at least 11x17 prints? Are lasers that much better than inkjets? Also, some good software for enhancing photos? Rogan Stroud Inkjet printers are your only real alternative for printing 11x17 images at home. The good news is you can achieve phenomenal results - if you're willing to take the time to learn and understand the printing process. Gary Stanley's column this month is a good start on learning and understanding the process. As for software I'd recommend one of the following programs: Photoshop CS, Photoshop Elements, or Paint Shop Pro 8.0. It will be quite a while before you're able to push the limits of any of these three. As for what brand of printer is best I'd recommend looking at Epson, Canon and now HP. Up until a few months ago HP wouldn't have made that list, but their new Designjet 130 really impressed us at PMA. When choosing a printer compare features and decide what is most important for your needs. Whichever printer you choose, start out using that companies inks and papers. Don't start experimenting with other papers until you're really comfortable with the process. While shooting today I noticed particles, which could not be removed from the focus prism plate- All dust was removed from the focus mirror and the external lens. The particles have accumulated inside the camera compartment (between the view finder and focus plates.) As you can tell I am not a professional, but have only had my camera since Dec. 2003. Any recommendations as to how to remove these unwanted particles? Canon Rebel Ti- EOS / SLR Thanks - P Win The dust that you are talking about is on the prism. You will not be able to get this out yourself. Dust in this area will not affect your images. The only optics that will have an affect on your images are the front and rear elements of your lens. The prism only reflects the image from the lens to the viewfinder so you can see what you will be photographing. If you want it cleaned out, the camera would have to go in to a service center to be disassembled and cleaned. Most repair centers that I've talked to over the years consider this a cosmetic job and don't recommend it unless it is interfering with the actual operation of the camera. Taking the camera a part and reassembling it is an expensive job and may not be worth the money unless there is an operational problem. Since the camera is so new you may want to contact Canon. If the dust is excessive they may consider cleaning it out under warranty. But don't be too surprised if they won't. Can I set my Nikon SB-80DX flash to fire remotely without wires using a D100? Thanks, The short answer is yes, but you'll need a second flash unit to trigger your SB-80DX. As a trigger flash you can use either the SB-30 or SB-50DX. For an explanation of how this is done check out The Nikon Infrared TTL Flash System from issue #22. |
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With
over 15 years of retail and professional experience Chuck thought he'd
heard it all - until he took this job.