Extension Tubes vs. Teleconverters, 2009 Digital TV Transition Questions, SmartMedia is dead

Sound Advice
By Don Lindich

Week 40, 2007

I was wondering how you felt about extension tubes. I bought one that does not seem to work. I have a Canon 20D and was using the extension tube with my Canon zoom lens EF 75-300mm. I know you can’t use the autofocus so I did change to manual mode. When I use it nothing far away comes in focus at all. Am I doing something wrong?

-Lisa Polidora, Wildwood Crest, NJ

A: Extension tubes, hollow tubes which fit between the lens and camera body, are used for close-ups so your lens can get closer than they can without them. They don’t help when photographing distant objects, as you have found out!

If you want to bring distant objects closer, the accessory you are looking for is a teleconverter. A teleconverter has lens elements that double the magnification without changing the focusing characteristics of the lens. Because you are inserting extra glass elements in the optical path, some sharpness is lost as well. The amount lost depends on the quality of the teleconverter. They work best with telephoto lenses such as the one you are using now. They don’t work well with wide-angles or wide-angle zooms.

The most common teleconverter, a 2x, would turn your 75-300 lens into a 150-600mm lens. The f-stop changes as well, by a factor of a stop per magnification factor, so a 2x would take your lens from f/4.0-5.6 to f/8.0-11. This is very dark for a starting f-stop and pretty much useless in anything but bright light, or with a tripod. Since you will have a very long focal length if you decide to get a teleconverter, a tripod is best used anyway.

As you can see, teleconverters have a lot of limitations. It is for this reason I rarely recommend them. It is better to buy an inexpensive long telephoto lens than modify an existing one, unless it starts at a bright f-stop such as a constant f/2.8.

Q: I am completely content with my current TV set up, which is 4 TVs with VCR/DVD combo units and Comcast extended basic cable. I record everything I like to watch at my convenience. Will I still be able to do this when the analog – digital switch occurs in 2009 since I do have cable, or will I have to buy 4 new television sets? I don’t really care about receiving the HD quality material I just want to watch what I like taped on demand.

Sarah McDowell, San Jose, CA

A: You will be able to do it, but you may need a converter box from Comcast. It will connect to the VCR/DVD combo units, then to the TV. I would check with your local office to see what extent they are converting their system.

Q: I have a Fuji Finepix 2.0 megapixel digital camera purchased several years ago. The camera uses SmartMedia memory cards. Apparently, these memory cards are no longer made. Is there any substitute that would work with this camera?

-Eliot Rothenberg, Minneapolis, MN

A: There are no substitutes, sorry. If you want to find a Smartmedia card I’d suggest trying eBay, where a 128MB SmartMedia card sells for $50 or so. That’s incredibly expensive for 128MB. and your camera is quite obsolete. I’d recommend upgrading to a new camera. Even an inexpensive currently produced $150 camera is likely to startle with you by how much better they are compared to your 2.0 megapixel model.

Comments are closed.