Lens information help

I want to buy a good lens, but I have no idea what these information means or represent, " 70-200 mm f4, or 55-200 f1.4 ,etc." for example?.
Could some one help explain what the first # and second # means. Does f2 is better than f4 etc.?

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Permalink Reply by jadeast on May 12, 2008 at 8:37am: it all depends on what you are expecting of your lens. Both examples of mm that you cite are zoom lenses. If you assume that 55 mm represents how your eye would view somthing then 200 mm would give you approximately 4x magnification. with many digital cameras these numbers may be different. The F number represents the amount of light that is transmitted through the lens in relation to the amount of light that exists, with f1.0 representing the all the light being tranmitted. In general the lower the f number the more expensive the lens may be. If you are going to be shooting in low light situations, by all means invest in a lens with a lower f number, if not f4 may work for you, but I might suggest that this number is marginal. I hope this helps.; ▶ Reply to This

Permalink Reply by Ragai Karas on May 12, 2008 at 10:42am: Thank You for your reply. I'm yousing a digital camera, Nikon D40 X and I like to shoot Bird in a very detailed. there are so many lenses available but as I said , which is better to buy.; ▶ Reply to This

Permalink Reply by jadeast on May 12, 2008 at 11:49am: I can't say which is best, what is best for me is not best for you, I just purchased a camera with 650 mm @f2.7 because I am going to be doing some long distance photography but I would like to have more power but I can't justify the expense. Getting back to your original question f2 is definitely better than f4 and if I had to make a choice between a 55-200 mm f1.4 and a 70-200mm f4 I would choose the 55-200mm f1.4 every day of the week. for photographing birds in at a distance in great detail I would go for more than 200mm.; ▶ Reply to This

Permalink Reply by Ragai Karas on May 12, 2008 at 12:49pm: Great Thanx; ▶ Reply to This

Permalink Reply by Howard Harrington on May 20, 2008 at 3:22pm: I use the 55-200 mm, for most of my zooms, the one for the d40, and d40x should be vr (vibration reduction) so a tripod is not always needed, I have not noticed any distortion in the lens, us a clear digital lens to protect it, or any decent filter, have fun, and shoot !!!; ▶ Reply to This

Permalink Reply by Ragai Karas on May 20, 2008 at 3:58pm: Thank you for your reply. I have no problem with my 55-200 mm zoom lens. It is just, I could not get the same crispy,details of the distant birds like the ones I see some time from other photographers. That is all,and I keep wondering about that.; ▶ Reply to This

Permalink Reply by Dimitris on May 19, 2008 at 4:17am: I tottaly agree with jadeast.
I will add that if you are going to use large zoom lenses, then you must have in mind that your fotos may easily become out of focus, so a tripod or something similar (even a "bean bag") would become very handy.
Also, keep in mind that the greater the joom, the lower the sharpness of the lense, especially if the lens is a common one.; ▶ Reply to This

Permalink Reply by Ragai Karas on May 20, 2008 at 4:03pm: How could be that "the greater the zoom ,the lower the sharpness of the lens". If that is true, then how come we see photos of birds shot from distance are so clear and very sharp !. This is what I'm looking for in a lens.; ▶ Reply to This

Permalink Reply by Christopher Rye on May 20, 2008 at 5:31pm: I think what Dimitris means is that if you get a lens with a large variation in focal length (#mm) such as a 70mm-300mm lens, than you lose some clarity and sharpness. If sharpness is a factor in your decision than I would suggest getting a fixed tele-photo lens, not a tele-photo zoom.
Example: if the focal length is "200mm" its a fixed lens, whereas "70mm-200mm" would be a tele-photo zoom so it would have a variable focal length. Hope that was helpful!; ▶ Reply to This