Lens Confusion

[LiveStrong2009]

I am in the process of picking out my first DSLR. I have decided that the xsi is probably the right camera for me, but as we all know, the kit lens is not very good. Although I would still buy the entire kit, buying another lens has been recommended.

I am looking at the B&H website. Other people on here recommended a 50mm 1.8. I also see on the website a 50 mm 1.4 and a 50mm 2.5.

What exactly do the numbers mean? What is the difference between a 1.4, 1.8, and 2.5?

 

[Johnboy2978]

The difference is in the aperture of the lens. That is, how wide the diaphram is able to open to let in more light. The smaller the number, the larger the opening. You also see the price increase as the number goes down from 2.5 to 1.4, but the build quality also goes up along w/ the price. By having a larger aperture, you are able to shoot at a higher shutter speed, hence, you will hear people refer to a 50mm f/1.4 as a "fast" lens. Lenses such as those w/ apertures between 1.4 and 2.8 are generally considered more of the pro quality lenses and are used for weddings and portraiture, etc. Always buy the best quality you can afford as a nice lens tends to retain it's value if not appreciate in value and you can almost always recoop your money if you decide later to sell it.

 

[reznap]

For the record, many people consider the Canon 50mm 1.8 lens one of the best deals to be had at roughly $100.

Canon also makes a 1.2 50mm... think it sells for like $1,200..? You pay a lot for an f-stop..

 

[pbelarge]

LiveStrong
What type of photography are you interested in shooting?

Such as; portraits, landscape, birding, sports, architecture, etc...
It may help people here to help you decide the type of second lens you may purchase.

 

[Felix 222]

DON'T buy a second lens yet. Spend a few months using the equipment you have. This will allow you to asses what lens you want or need.

The kit lens is decent and you can take amazing photographs with it.

 

[KmH]

....The smaller the number, the larger the opening.....

Well, sort of anyway and there are some pretty decent kit lenses these days.

The number is actually a ratio which most people just call a fraction.

On the lens it looks like 1:1.4, or 1:1.8, or 1:2.8. Or it may be a range like 1:3.5-5.6, meaning the lens has a variable maximum aperture.

1:1.4 means the diameter of the largest aperture opening in the lens is equal to 1/1.4 the focal length of the lens.

Lets do the math ( I love doing math): We will consider a lens having a 100 mm focal length to keep it simple. 1/1.4 in decimal is 1 divided by 1.4 = .714

So 100 mm x .714 = 71.4 mm The lens opening is 71.4 mm wide. At f/2 (1/2) the lens aperture is 50mm wide (100 mm x .5 = 50 mm) and at f/4 (1/4) the aperture is 25 mm wide.

If you consider a 50 mm lens each of those red numbers would be 1/2 those values because the focal length was reduced by 1/2.

So, the truth is 1:1.4, being a fraction, is actually a bigger number than 1:2.8 is.

 

[white]

I am in the process of picking out my first DSLR. I have decided that the xsi is probably the right camera for me, but as we all know, the kit lens is not very good. Although I would still buy the entire kit, buying another lens has been recommended.

I am looking at the B&H website. Other people on here recommended a 50mm 1.8. I also see on the website a 50 mm 1.4 and a 50mm 2.5.

What exactly do the numbers mean? What is the difference between a 1.4, 1.8, and 2.5?

The numbers refer to f stops. Maybe you should spend more time learning about the basics of photography before you go out and buy glass that may not suit your needs.

 

[LiveStrong2009]

Thank you everybody for the replies! Lots of this photography vocabulary is a bit confusing to me. I am slowly getting the hang of it and understanding it more and more. Can any of you recommend a good book to help me understand how some of this works?

At this point, I have been using a Nikon P&S. Despite the fact that it is an excellent P&S for the price I paid, I believe I have reached its' limits. Unfortunately it did not have many user options while shooting, beyond exposure and ISO.

I am intending on using the camera/lens primarily for landscapes, architecture, and macro is also interesting to me.

 

[Johnboy2978]

Understanding exposure - Bryan Peterson

 

[cpolaris502]

I second the notion on using the kit lens for a while and getting the feel for it to help you decide what type of second lens you will want to get. That way you wont end up buying a lens that you may not use all of the time because you didn't know what it would be like.

 

[mwcfarms]

The kits lens is a perfectly good lens to learn on. We all have to walk before we can run and I second the book Understanding Exposure. Its well wrote and very informative. Good luck and cant wait to see some shots.

 

[djacobox372]

DON'T buy a second lens yet. Spend a few months using the equipment you have. This will allow you to asses what lens you want or need.

The kit lens is decent and you can take amazing photographs with it.

I agree, but I would say, don't buy a kit lens yet. Buy the 50mm f1.8 as your first lens, and then assess what else you need.

When you buy a kit lens, you typically end up replacing it with something better in the future--you will never need to "replace" your 50mm f1.8.