Friday, November 30, 2007

December 2007 HelpLine

December 2007 HelplineStep Up To A Larger Filter

Q) I'm about to purchase a 28-75mm lens for use with my digital SLR. It has a 67mm diameter lens; however, I have a 77mm circular polarizer that I would like to use with the new lens. I also plan to purchase a 67-77mm step-up adapter so that I can use these larger filters on the smaller lens. My question is, how will the quality of the image be affected by not using the exact size filter required, i.e., a 67mm polarizer on a 67mm lens?

Lindsay Miller Published in HelpLine
December 2007 HelpLine



Switching To A D-SLR

December 2007 HelplineQ) This question takes a recent question by Ed G., "A More Stable Lens," a little further. I primarily use my digital camera for vacation photos to be put in slideshows. It's nearly perfect, except since it's not an SLR, I can't see well what I'm shooting, especially in bright sunlight. In considering switching to a digital SLR, one of the things I don't want to give up is the ability to take fairly decent photos in low light. I was able to take photos in the redwoods while it was raining slightly, something I couldn't do with my film SLR.

What is it primarily that enables the camera to do this? Is it the image stabilization? Is it the fast ƒ/2.8-3.5 lens? Is it something inherent with digital SLRs, or is it a combination of all the above? In other words, how do I assure that a D-SLR I purchase will be able to take photos in low light?

A single 18-200mm digital lens is what I'm thinking about. I really don't want to go back to changing lenses again. I especially don't miss my big 400mm lens. Due to time constraints, I rarely use a tripod anymore, so image stabilization is a must.

L. Malott
Via the Internet

A) You're referring to the October HelpLine where Ed G. was looking for a lens recommendation or, more specifically, advice as to whether it made sense to spend the extra money for a lens with stabilization. In my answer, I discussed ISO speed, use of tripods vs. handheld and bank accounts.

Now that was Ed, but you're concerned about the performance of a digital SLR in low light. You mention you weren't able to take photos in the redwoods with your film SLR. You probably could have, had you been using high-speed film.

One of the amazing features of digital cameras is the ability to change the apparent sensitivity of the camera's sensor with just the press of a button—okay, so it might be a few buttons on some cameras! (I say "apparent sensitivity" because you're really amplifying the signal coming from the image sensor—the sensor has only one native sensitivity.) This is something you could never do without changing rolls in a film camera. With high-speed film or a high-ISO speed setting on your digital SLR, your camera can work in lower light levels. With higher ISO speeds, you can also raise your shutter speed so you can handhold more shots with less blur.

Just like increased film grain with higher-speed films, there's a trade-off with raising the ISO speed: noise. As you increase the amplification from the image sensor, you amplify noise in your image. But the low-noise characteristics of the latest digital SLRs are pretty amazing.

You also ask which part of the equipment equation allows you to take photos in low light: the fast lens, image stabilization or something inherent in the technology. Certainly, the faster the lens, the more light reaches the sensor, allowing you to photograph in lower light. Stabilization allows you to lower your handheld shutter speed, which also allows you to photograph in lower light. By coupling a fast lens, image stabilization and the ability to quickly change ISO speed, I think you'll find that today's digital SLRs will perform well in low-light situations and most likely will perform better than the compact digital camera you're currently using.

One last word about time constraints not allowing you to use a tripod. If you have been following my columns, you know I'm a strong proponent of using tripods. But I realize that it can't always happen. If time is an issue, consider using a monopod. They can be quick to set up and easy to carry. While they don't give you the complete stability of a tripod, they can help quite a bit.

 

 


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