Originally posted by alamo5000 I have seen some lenses that have apertures from 1.4....some with 1.7...some with 2.4 and so on and so forth...assuming focal length is standard really what would be the 'big difference' between a 1.4 and 1.7 and 2.4 or so on and so forth?
Well, one thing is for sure... with faster lenses it is easier to start an argument over the definition of bokeh...
Originally posted by Anvh Does it sound more interesting that way?
Luckily, I'm still new enough that I can still impress my friends with words and phrases like "aperture" and "depth of field".
As for the original post... my 2 cents:
A larger aperture gives you the ability to let in more light, faster than a smaller one. This is useful for the subject isolation and out-of-focus background reasons mentioned. It is also useful when shooting fast moving things in low light. Fast moving requires fast shutter speed which reduces the amount of time light can hit the sensor. Your options are to make the sensor more sensitive to light by upping the ISO which creates noise in the image or use a larger aperture so that more light gets in faster.
As others have mentioned, in general, lenses will be sharper when stopped down a little from their widest setting. However, whether a particular f/1.4 lens will be sharper at f/2 than some other f/1.8 lens at f/2 is really up to the lens. For this reason, I highly recommend consulting the lens reviews on this forum often. It will be those reviews and viewing sample images shot with the lenses in question that will help you decide which lenses are right for you. Even when it comes to (and I hate to say it) bokeh. Hopefully most will agree that it is subjective and what I prefer, you may not. Or like Rio Rico, you'll learn the characteristics of several lenses and select the one that can create the image you're going for.
The other alternative is LBA. Just buy a dozen lenses, shoot with them all and then sell off the ones you're not using. If you're careful about buying, they really don't depreciate much (if at all). However, the drawback is that selling them is easier said than done. I can personally attest that this method is highly educational though. However, as I am also on a budget, I mostly avoid eBay and instead frequent garage sales, estate sales, goodwill and pawn shops. I have found that pawn shops (at least by me) price their lenses based on mass. That is to say that big heavy lenses are $100 or more and small lenses are $20 or less. This works great when shopping for fast 50mm and/or close focusing 28mm lenses!
Ok, so that was maybe 4 cents worth. But from one newbie to another, there ya go.