Newbie Lens Question??

mw0dbb

mw0dbb

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John
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Hi all, I'm pretty new to camera's etc... And I'm having a problem getting my head around all the different lenses out there! What I want to know is what is the difference with fixed "f" number lenses? I mean they seem to be alot more expensive, why is this? Also I am not sure what the difference is with macro lenses? I know they are better for detailed close up pics but can they be used for normal pics etc...?

I am intested in all types of photography especially nature and landscapes! Would also like to do some night time photography. I have a Canon 550d with the standard lenses that come with the camera.

John
 
which were the 'standard lenses'? do you mean the 18-55 IS, and the 55-250 IS ??

(or did you get some others)
 
Fixed f number lenses give the f number across the full range e.g. a 70-200 f2.8 will be 2.8 from 70 to 200 whereas a lesser lens would be maybe 4.5 - 5.6, letting less light in and therefore less useable under lower light conditions than the other. This is more expensive to manufacture, hence more costly to buy.
A macro lens will enable close-up photography but will also allow normal use, so for example, a 200mm macro will still be a 200mm lens but can focus close-up unlike a non-macro lens which will have a limit to how close to the subject you can focus.
 
The lens I have are 18-55 and 70-300 but they are not IS or USM. That makes is alot clearer gramps. But I'm am not sure what the advantage is? I mean in terms of what it does to a pic?

John
 
mw0dbb said:
The lens I have are 18-55 and 70-300 but they are not IS or USM. That makes is alot clearer gramps. But I'm am not sure what the advantage is? I mean in terms of what it does to a pic?

John
Click to expand...

USM lenses can focus a bit quicker.

IS Lenses (with built in Image Stabilisation) allow you to take steadier shots when shutter speeds need to be a bit slower. The 'effectiveness' of the IS system in different lenses is often rated as being 'worth' X amount of stops.
 
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I also have a Canon 550d...

I shoot landscapes and have the Canon 10-22 - great for wideangle.

24 - 105 IS F4 L lens. This is a great lens for general use. The IS is the image stabilisation which means you can shoot at slower speeds than normally recommended and still get sharp images.

Then I have the 70 - 200 / F4 L lens. This is a great lens for telephoto.

Also because the 550d camera is not full frame, but 1.6 a 70 - 200 actually becomes
112 - 320 on a old style 35mm, so it becomes quite a long lens.

I strongly recommend the Canon "L" range. They are more expensive, but well worth it. I mean why spend decent money on a good camera then stick a milk bottle in front of it.
Probably more of a consideration when you really get into photography.
 
Ah sorry I was on about the fixed "f" lenses.
 
I did look at the L class lenses, but they are well out of my range! This is just a hobby to me and I cant really justify that amount of money for a hobby, however who knows if I have a lotto win!!

John
 
mw0dbb said:
Ah sorry I was on about the fixed "f" lenses.
Click to expand...

Well a 17-55mm f2.8 for example allows you to use the maximum aperture of f2.8 all the way from it's widest 17mm to it's longest 55mm. This means it's a constant aperture lens and you don't need to use a slower smaller aperture as you extend the focal length.

Where you see f4 - f5.6 on a lens it means that f4 is the maximum aperture you can use at it's shortest length but the max aperture is only f5.6 when the lens is extended to it's longest focal length. This would mean that you loose light and therefore have to adjust shutter speed (or increase ISO) as you extend the lens.
 
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Further, when you zoom a lens from wide angle to the longer end the ratio of front element size to focal length goes down. In a non-constant aperture lens this would mean less light getting to the sensor, i.e. a smaller f-stop. Paradoxically F-stop numbers get bigger as the light transmision power gets smaller. So, as Phil says above, at the wide end there is more light, and hence a smaller f-stop number than there is at the longer end. To ensure constant maximum aperture throughout the lens's zoom range involves more glass and complex zoom mechanisms which both cost money. The advantage is obviously consistent light transmission through the zoom lens, but usually the more expensive lenses are sharper as well.
Incidently, to explain the weird stop numbers, F-stops double the light according to the inverse square of the stop number. Therefore F4, is double the light of F5.6 which is double F8 because 4x4 = 16, 5.6x5.6 = 32, 8x8 = 64 etc.
 
Sorry for being so stupid!! But surely having a low f number will give you less depth of field? I'm just wondering why you would want that in a lens?
 
Thanks for that dogfish, very useful tool. The girlfriend and myself are getting into photography and she is always asking about the settings!! Will give her a better insight.

As for the lenses, not sure why I would want to limit what the lens can do? But then again it is for a specific task! I think I will look for a wide angle lens as I like to do alot of lanscape pics and also some daylight long exposure shots.

John
 
Practice with what you have first, get to know your camera and then when you start to find your lens is limiting the type of shot you are after you'll have a better understanding of what to add to your set. I will say that I find the 55-250 IS is a more capable lens than the 700-300 and not a very costly Lens
 
Thanks for that Iris, I have been playing with the lenses I have and I do find there limits pretty easily! I have been also looking at the IS lenses as it may save me using the tripod all the time? Anyway I think I now have a better understanding of how the lenses work!
 
I can vouch for the 55-250 IS being a great lens. I got one off the forum a few weeks ago for £110 and it is a cracking lens. Very sharp, light and easy to carry and use and a very useful length on a crop body. I've used it on my 550D and my 7D and I'm very happy with it so far.
As for fixed f lenses, you can alter the camera to change the DOF, it's the light gathering capabilities of the lens throughout the zoom that makes them so desirable.
 
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mw0dbb said:
Thanks for that dogfish, very useful tool. The girlfriend and myself are getting into photography and she is always asking about the settings!! Will give her a better insight.

As for the lenses, not sure why I would want to limit what the lens can do? But then again it is for a specific task! I think I will look for a wide angle lens as I like to do alot of lanscape pics and also some daylight long exposure shots.

John
Click to expand...

Your not just stuck at f2.8. You can still go smaller if you want
 
Thanks for all the info guys.... At the moment I am not sure what I am looking for? I have a wide range of subject matter that interests me and no one lens is going to do that. I might even hire the odd lens to see what I like and see what gets the best results before I even look at buying. At the moment I just want to get a good basic setup which isn't going to cost the earth!

John
 
Cheap and easy way of getting superb and very high quality landscapes - panoramic technique.

Take several overlapping images of the view, then load them into software which merges them automatically into one massively wide view, as wide as you like.

If you have Canon, they supply PhotoStitch software free with the camera. Or you can download others free from web.
 
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