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09-07-2007, 09:56 PM   #1
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Join Date: Sep 2007
Location: Colorado
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Just thinking out loud here.

First of all I have a Pentax *ist dl that I bought in May of this year and I think it is the best thing since sliced bread. Now since my money has been kinda tight with this I bought a lense that isn't all that fast. I like photographing wild-life (from a distance), flowers, moon and so forth and so on.

What I have is a:
Promaster 28-80mm f/3.5-5.6 (came bundled with the camera when I bought it)
Tamaron AF 70-300mm f/4-5.6 (I bought about a month later brand new)

If I go and purchase the same lenses in a faster f stop I would probably end up selling these lenses I think. Because the original lenses I have would be slower and why would I want to shoot with a slower lense when I have faster lenses. I also use a 1.4 teleconverter with my lenses to get even closer to the subject.

Does this make sense? What I'm trying to do is come up with a plan of getting faster lenses and get rid of my slower lenses.


09-08-2007, 05:05 AM   #2
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Join Date: Jul 2007
Location: Sault Ste Marie, Ont, Canada.
Posts: 563
Faster lenses only do a few things for you. They will allow you to shoot in lower light with a faster shutter speed simply because they allow more light in. The second thing they will do for you is to decrease your depth of field with a larger aperture.

The trade off is of course price and weight. It is amazing at how much more glass is required to make a faster lens.

A lot of people do not need really fast lenses unless your planning on doing natural light hand held photography in low light conditions, or your trying to blur the background on your main subject.

One could almost argue that if you’re going to put it on a tripod, and or use a flash, you could get away with a slower lens...depending upon your subject matter. If it moves, a slower shutter speed will not be your friend.

If you take the same lens, one is an f2.8, and the other an f4, and only use the sweet spot (on many lenses this is f8), you could argue that having the faster lens is a waste as they are both being used the same. Mind you, it is possible that the f2.8 variant might have better glass translating into a better photograph (or it could even be worst then the slower lens). But my point is that, all things being equal, having a faster lens isn't always the best solution. Often, depending upon what you’re doing with your gear, it can be a complete and utter waste.

Yes, I know some people will say that the lenses are an investment, and they are right, and good glass never goes to waste, and that is true enough.

My most used lens is a Sigma 50-500mm as I enjoy shooting wildlife a lot. It is a terribly slow lens that goes right up to f6.3 at the long end. However, since my shooting is usually during the day, I find that I can get 1/500+ shutter speeds at ISO100 quite easily. At 500mm the depth of field is so narrow anyways, that a faster lens wouldn't really do me any good.

As for poor lighting conditions, I most often use a flash with a diffuser on it. Either that or the camera goes on a tripod. I really do not notice the lack of a really fast lens

I guess my point is that faster lenses aren't always better lenses. You may find that you rarely used them to their full potential. Evaluate your needs, and if you find that a faster lens is what you need, then your plan makes perfectly good sense.

EDIT: I also would like to add that a faster lens will allow you to autofocus in lower light then a slower lens. This could be a big plus to consider.

Last edited by Chako; 09-08-2007 at 05:36 AM.

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