Understanding Lens Speak

[Kirislin]

I feel dumb fessing up but my manual doesn't explain this and I still dont really understand all the specifics of lenses. I'm getting a handle on f/stops but what exactly does the 18-55 and 75-300 mean on my two kit lenses? Yes I understand one is a zoom, that, putting it simply, brings far away things close, but I dont really understand the figures, other than knowing they're measurments.

the lens a few of you speak highly of and I think I want, 50m 1.8, is it so different from the 50 1.4 which is hundreds of $$ more? Why the huge difference. And I see alot of lenses that dont seem to vary alot and yet there seems to be a specific purpose for all of them.

I want to be able to understand what I am reading when I trawl the for sales but with all the numbers and letters I am just bewildered and feeling very much out of my depth :cool:

[persephone]

Can't help you... numbers :cool:

have a read HERE

There are some explanations...

[Kirislin]

Thankyou Persephone, I shall wade through it. I think we should start another forum here: ask Persephone :cool: cause you just about always can point me in the right direction.

[Ashanali]

the price difference between the 1.2, 1.4 and 1.8 is due to many factors (if you are talking about Canon).

The 1.2 is an L series lens. These are top of the line, with high quality glass

1.4 is also high quality but a step down from the 1.2 and doesn't have that lovely 'L' tag attached. (whilst I would love a 1.2 the actual difference in output is negligible between the two. I bought the 1.4 )

the 1.8 is very lightweight and cheaply made. Lots of plastic. A great lens for those shooting on a budget.

[Aubrey]

I feel dumb fessing up but my manual doesn't explain this and I still dont really understand all the specifics of lenses. I'm getting a handle on f/stops but what exactly does the 18-55 and 75-300 mean on my two kit lenses? Yes I understand one is a zoom, that, putting it simply, brings far away things close, but I dont really understand the figures, other than knowing they're measurments.

the lens a few of you speak highly of and I think I want, 50m 1.8, is it so different from the 50 1.4 which is hundreds of $$ more? Why the huge difference. And I see alot of lenses that dont seem to vary alot and yet there seems to be a specific purpose for all of them.

I want to be able to understand what I am reading when I trawl the for sales but with all the numbers and letters I am just bewildered and feeling very much out of my depth :cool:

Don't worry, you are not the first, and won't be the last to be baffled by all this talk.

I've just finished a photography course and have a much better understanding of it all now, so will explain a little and you can PM me if you have more specifics.

The 18-55 and 55-200 is the zoom lens. Generally it is done using old speak photography where the 35mm was the norm for photographs. However, with the zoom lenses rather than saying 2x, 3x etc, you can zoom to specific intervals.

This also depends on your camera. Most are a 1.5x which means at 18mm you are actually at 27mm and at 200mm you are at 300mm zoom. Either way, the larger the number, the closer you get to the subject you are photographing, but then the less of the surrounds you get.

On top of this you need to think about your f/stop which is basically the amount of light that is getting into you camera and to the sensor at the back. The sensor is a computerized version of film, which transfers the data into a digital image.

The more light, the brighter the picture... too much light = overexposed.... too little = under exposed. During normal conditions (good light) you can use the metering in the camera to get the best out of it. The more zoom you get, on the standard lenses, the higher the f/stop, so the less light that gets in, which means you either need really sunny days, or to open up the sensor more, which means slower shutter speeds in order to capture that perfect shot with the right light settings.

Which brings us nicely on to the 50mm lenses... of which I am trying to convince the OH to get me one for XMAS (If she reads this post!).

The 1.2 lets more light in than the 1.4 which lets more light in than the 1.8 and so on down the scale. These values can go up to 32 and beyond, depending on the zoom and the lens, and of course the camera.

The better the f/stop the better you can get the shutter speed, and therefore the crisper the image. For example in an average cloudy day, if you were trying to photograph your dog going on its zoomies you might get a blur if the meter has your shutter speed at 1/4 second because your kit lens is on an f/stop of 4. However, with the 50mm lens offering you a 1.8, you effectively gain 2 f/stops (4 to 2.8 to 1.8) which can also improve your shutter speed by 2... which may mean getting that shot at 1/20th or 1/15th of a second... much quicker and sharper. If you had the 1.4 then you could get away with the next shutter speed down, which is around 1/25th or 1/50th second, depending on your camera.

Most people rate these lenses at the lower light levels during the day, you get what you pay for with the well built lenses and the lower f/stop. A 50mm 1.8 is currently around $200 (damn US $) and the 1.4 is around $400.

The lens also plays an important part in the best shutter speed to use, and IS / VR gives you 2 shutter speeds to assist. Rule of thumb I've been taught is that the slowest shutter speed is 1/ the longest zoom of the lens (so 1/50th and 1/200th second for your two lenses). Any slower than that and you'll get blur caused by camera shake (average user without the shakes due to a hangover here!). So you have done what I did which was get 2 lenses to cover the range that 1 lens can do, and that will probably give you better photos at the closer ranges.

Hope this helps, the more I try and explain it to others the better it seems to get in my head!

Andrew

[chezzyr]

Kirislin: the 50mm/1.8 (Canon) is little and light and some would think it looks/feels more

like a toy than a real lens. Don't let the exterior fool you - it can take great images!

I will let the others take the floor with techno speak but am happy to email you some

samples (though you may have seen them already, I think I have posted some

elsewhere) :cool:

[persephone]

Ok...

now I'm embarrassed :cool:

but these are links to a friend's photos... with different lenses... they may be of help?

10-20 mm 1:4 5:6

50 mm 1:1.8

50 mm 1:1.4

and

75-300 mm 1:4 - 5.6

I get horribly confused with tech-speak and numbers, and have to use examples like this to drive the point home

*leaves thread....*

[Ashanali]

Most people rate these lenses at the lower light levels during the day, you get what you pay for with the well built lenses and the lower f/stop. A 50mm 1.8 is currently around $200 (damn US $)

Nope.

http://www.shopbot.com.au/p-32489.html

the 50mm 1.8 is $124 at camerasdirect (and I highly recommend them).

[Aubrey]

Most people rate these lenses at the lower light levels during the day, you get what you pay for with the well built lenses and the lower f/stop. A 50mm 1.8 is currently around $200 (damn US $)

Nope.

http://www.shopbot.com.au/p-32489.html

the 50mm 1.8 is $124 at camerasdirect (and I highly recommend them).

I'm on the Nikon so a 50mm 1.8 is $150 at best, or $174 from local shop

http://www.shopbot.com.au/p-31595.html

[Gayle.]

The numbers on the lenses are the distance the lens sits from the film plane (or the sensor on a digital camera). The closer it sits, the wider the view you've got through the lens.

Here is a really simple experiment to help you understand it. Take the cardboard tube from inside a toilet roll. Hold it up to your eye and look through it, take note of how much you can see.....ie, the field of view.

Take a pair of scissors and cut a slice off the end.....about 2cms wide. Now you have a very short tube, look through it and see how you have a much wider field of view than with the much longer roll.

That's a very simplified explanation, but should give you an idea of the basic structure behind a lens and what the numbers mean. Your eye is the "film plane", the end of the tube is the lens.

Of course, it's much more complicated than that, lenses have a series of magnifiers and mirrors to enhance the view, and the glass on the end of the lens is not where the measurement is taken from, but hopefully this will help you understand it.

With a zoom lens, the actual lens mechanism moves forwards and backwards as you rotate the tube, moving it further or closer to the film plane (or sensor) as you zoom in or out....therefore changing the field of view you can see. You can experiment with two cardboard tubes, one inside the other, and move one in and out.......viola, a simple zoom lens.

So, the higher the number, the further the lens sits from the sensor, the narrower the field of view. The lower the number, the wider the view you have because the lens is sitting much closer to the sensor.

Hope this helps you understand it!