Wednesday, October 8, 2008

Acquiring New Lens

The photography gear that I own is based on the Canon EOS system, specifically the EOS-5D. I also own a Canon PowerShot A650 IS point-and-shoot camera for taking on my business trips. I'm planning to acquire the Canon EF 70-200mm f/2.8L IS USM lens in the coming days. It will nearly round out the lenses that I feel that I need. One lens that will still be missing is the EF 14mm f/2.8L II USM. That lens will replace the Sigma 14mm lens that I had previously. There are other lenses that I would like to have, but my sights are on all "L" series lenses and they are expensive. I've considered such lenses as the EF 300mm f/2.8L IS USM, the EF 180mm f/3.5L USM Macro, the EF 24mm f/1.4L II USM, and a wide-angle tilt-shift lens. I suppose if I had to prioritize those lenses, I would get the tilt-shift lens as it would allow me to experiment with something new.

I think that this coming weekend, I am going to get my 85mm f/1.8 prime lens out and take some pictures with it. I've had that lens for six months or so and have not used it much. I'm also going to take the opportunity to use my Expodisc. For those not familiar with the Expodisc, it is a diffusing disk that clicks onto the end of the lens. It doesn't stay there, but it serves two purposes while it is there. It transmits 18% of the light falling upon it, and it is neutral in tone. The 18% number is significant because that is medium gray. You snap the Expodisc onto the lens, then set the camera to Manual mode, then you choose your aperture or shutter speed and dial it in. Then you adjust the other parameter (shutter speed or aperture) until the camera's exposure meter says that you have a proper exposure. You need to make sure that the camera is bathed in the same light that the subject will be, which works perfectly on a sunny day. Once you are in the proper light, you snap a picture. Then you configure the camera for a custom white balance. Most cameras will ask you to choose a picture to base the custom white balance off of. That picture will be the one you took previously of the Expodisc. Now you remove the Expodisc and put it away. You leave the camera in Manual mode. Assuming the lighting stays the same, the exposure settings will stay the same. You can always change the aperture or shutter speed, but you have to change the other value accordingly. For example, if you had initially chosen f/4 at 1/500-sec, and you wanted to go to f/8. That's two stops. You need to lengthen the shutter speed by two stops. For shutter speeds a stop is either a doubling or halving. In this case, a one stop change is 1/125-sec, and two stops is 1/60-sec. 1/60-sec is the new shutter speed. Using a tool such as the Expodisc or an external incident light meter is especially beneficial when the lighting is tricky. The Expodisc is a fairly new product, but I've been using an incident light meter for years (until recently a Minolta Flash Meter IV). I believe my first use of the light meter was to determine the proper exposure for a snowy scene. I've read several books and websites that simply say if you have a sunlit snowy scene, then overexpose by such-and-such stops, but no matter what number they mention, I cannot remember. For me, it is easier to use the light meter.

Assuming that I take some pictures this weekend, I'll try to post them to my Picasa site.