simple lens Q ?

minister · Jul 21, 2010

Hi,

as I am noob I have right to ask silly question

hear I goes - I have 18-55 kit lens
as far as i understand I can shoot 18mm wide shot and 55mm narrow shot

my confusion is if I wanted to shoot a wide angel , why to buy those small focal length when I already have 18mm wide available ,

and why those small number wide angel lens say 24mm so expensive because the aperture they provide, my best guess !!!

my simple question is what would i achieve with those small focal length lens what i can't get with my 18-55 mm :meh:

oldmacman · Jul 21, 2010

If you are using an 18-55, I'm going to assume you have a crop sensor, APS-C, sized sensor. This means to determine your actual focal length, you multiply the number by its crop factor (1.6) for APS-C. So your 18mm end is really a 29mm, more or less.

The same would go for the 24mm.

Yes, the aperture is part of the reason the lens will be more expensive, but there are other factors like:
- improved optics
- build quality
- flare control
- sharpness

Until you get really good at photography,or you need to make larger prints, your kit lens should serve you well.

Dao · Jul 21, 2010

Because they are different. Different in build quality, optical quality as well as other performance factors.

A lens usually cost more when ...

- It is well build and solid. Some of them even have weather seal.
- It has great optics so that the final image is sharp and less optical issue such as distortion or CA.
- It has build in image stabilizer.
- It has fast quiet autofocus motor.
- It has a large max. aperture.

So in your case, I believe the 24mm lens most likely is a faster lens (larger max. aperture), better build and optically better than your stock kit lens. And therefore cost more.

rusty9 · Jul 21, 2010

well, it provides a larger aperture (which is more expensive) so it performs better in low light. the lenses you mentioned have better build quality, too. and those lenses have less zoom range. the more zoom it has the less quality. so that is why primes are better than zooms.

rusty9 · Jul 21, 2010

dang it. you two beat me to it.

TiCoyote · Jul 21, 2010

All of those factors are correct (build quality, optics, aperture, etc.). Also, wide-angle lens is a bit of a different animal. The lens is round, so it wants to produce a round image. However, the sensor is rectangular, so the image needs to be focused in a way that's rectangular. Refocusing a round image in a rectangular format is tricky, and therefore expensive. If you just let the image focus so that it was round, you would have a distorted image. A fisheye lens allows it to focus a round image. Essentially, a fisheye is a wide angle lens that does not produce a rectangular image. You will notice there are quite a few inexpensive fisheye lenses for this reason (amongst others).

Robin Usagani · Jul 21, 2010

Minister, if you really want the "wide angle" feel on your camera, you have to by 10mm or 12mm because your sensor is cropped. The expensive fast wide angle lens are really meant for a full sensor. If you buy that expensive lens and use it on your camera, it will be a like a fast zoom lens.

Dao · Jul 21, 2010

Schwettylens said:
The expensive fast wide angle lens are really meant for a full sensor. If you buy that expensive lens and use it on your camera, it will be a like a fast zoom lens.

:scratch:

minister · Jul 21, 2010

TiCoyote said:
All of those factors are correct (build quality, optics, aperture, etc.). Also, wide-angle lens is a bit of a different animal. The lens is round, so it wants to produce a round image. However, the sensor is rectangular, so the image needs to be focused in a way that's rectangular. Refocusing a round image in a rectangular format is tricky, and therefore expensive. If you just let the image focus so that it was round, you would have a distorted image. A fisheye lens allows it to focus a round image. Essentially, a fisheye is a wide angle lens that does not produce a rectangular image. You will notice there are quite a few inexpensive fisheye lenses for this reason (amongst others).

I had this Q also in my mind you just cleared

minister · Jul 21, 2010

I am very thankful you all are so help full to clear my doubts

Robin Usagani · Jul 21, 2010

Dao said:
Schwettylens said:

The expensive fast wide angle lens are really meant for a full sensor. If you buy that expensive lens and use it on your camera, it will be a like a fast zoom lens.

Click to expand...

:scratch:

what? PUt a 24mm on a crop sensor, what will that do?

Dao · Jul 21, 2010

But it will not change into a zoom lens though.

Robin Usagani · Jul 21, 2010

it zooms in and out does it? It is not prime.

Dao · Jul 21, 2010

hum .. ok .. I thought when OP said "those small number wide angel lens say 24mm so expensive because the aperture they provide", he meant 24mm prime lens because it has only one fix focal length.

Rosshole · Jul 21, 2010

minister said:
Hi,

as I am noob I have right to ask silly question

hear I goes - I have 18-55 kit lens
as far as i understand I can shoot 18mm wide shot and 55mm narrow shot

This is a DX lens. This is designed for the Nikon DX Sensor (1.5 crop APS-c). Because of this 1.5 crop, it has a effective focal length of 24mm on the wide end.

minister said:
my confusion is if I wanted to shoot a wide angel , why to buy those small focal length when I already have 18mm wide available ,

and why those small number wide angel lens say 24mm so expensive because the aperture they provide, my best guess !!!

Optically it is a better lens, it has a higher constant aperture, and is optically designed to cover a Nikon FX sensor at 24mm (same effective focal length as your 18mm. I am assuming that you are referring to the 24-70 2.8 Nikkor...