Difference between 2 Nikon AF Lenses?

Nikon 35-70mm 3.3-4.5 autofocus lens and Nikon 28-100mm 3.5-5.6 autofocus lens.
I'm getting the Nikon D70 with one of the two lenses but I don't know the difference.

Does the 35-75mm compared to the 28-100mm lens give a smaller range of focal points? So in that case the 28-100 would be better?

And what does 3.3-4.5 mean and what's the difference between that and 3.5-5.6? Is it the f-stops, how wide the opening of the lens can go to to get more light into the photos?

Which is the better of the two? I'm a beginner photographer so don't need anything fancy. These lenses are just what come in either package I might be buying the D70 with.

And this may be a obvious question, but can you take photos no background blur with these lenses by maximising or minimising the f-stop?

Yes, the 35-75mm does give a smaller focal range. While the 28-100mm gives a greater focal range, there are other factors in the quality of a lens, such as how fast it is, IOW does it give you a larger aperture.

3.3-4.5 is the aperture at each end of the focal range.f/3.3 at 35mm, f/4.5 at 70mm.

I would get the 28-100mm just because it gives more flexibility. 28mm is great indoors to get a wider view of things. 100mm is better outdoors because it brings those things further away in closer.

To minimize background blur, stop the lens down to its lowest size, IOW f/32 or whatever you can.

Each lens would be considered a "normal" zoom, and are pretty similar. The 28-100mm will give you a bit more range, both on the wide angle and telephoto ends.

For comparison, the normal "kit" lens for this camera was a 18-70mm. It provided a lot nicer range in the wide angle end, which with a cropped camera, would have an advantage.

The numbers 3.3~4.5 and 3.3~5.6 are apertures, and refer to the speed of the lens, and are the range of the maximum aperture. Speed means how much light the lens will pass. The term "fast lens" is usually used to describe the lenses that allow a lot of light in.

Technically speaking, the numbers are a ratio between the (focal) length of the lens, vs. The opening. So a 100mm lens, if it had an aperture of 2:0, would have a 50mm opening (100/2). Similarly, a 100mm lens with an aperture of 4:0 would have a 25mm opening (100/4). Since a 25mm opening is smaller (in this case half as large), it will only let in half as much light.

By the way, the correct way to refer to aperture is to use some form of f/ in front of the number. So f/2.0 would be the correct way to put the number down rather than 2.0. F is often called f-stop.

But it gets more technical.

In consumer-grade zoom lenses, they are known as variable aperture.So, f/3.5~5.6 would mean that the largest opening of the lens at the minimum zoom focal length would be 3.5x, while the largest opening at the maximum zoom focal length would be 5.6x (vs the diameter). While this is probably confusing, suffice to say that as you zoom in, your lens's ability to let in light is reduced.

And to make matters more confusing, the apertures on these lenses are adjustable. So at the shortest focal length, the aperture can be adjusted from f/3.5 to usually f/22. And at the longest focal length, the aperture can be adjusted from f/5.6 to usually f/22. Again, these numbers are a ratio of the focal length of the lens, vs. The opening diameter, so the larger numbers indicate a smaller opening.

So why all the fuss. The aperture is like the iris in your eye, and it opens and closes to help obtain the proper exposure (among several secondary purposes).

Having said all of that, when you compare the two lenses you found, the 28-100mm lens has more zoom range vs the 35-70, but has a penalty in that it can't let as much light in (f/4.5~5.6 vs f/3.3~4.5).So you have a bit of a compromise on your hands.

However, the good news is that the difference between the two lenses in light ability - even though the 35-70mm lens is better, is not significant.

I'm sure this is all confusing, but apertures are a rather advanced topic. Here is a link below to just one of hundreds of webpages that describe this topic:

http://www.althephoto.com/concepts/aperture.php

Edit:

You can minimize the background blur by decreasing the lens focal length, increasing the focus point, or decreasing the aperture (or a combination of the three).