Newbie question regard lenses.


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Jul 22, 2008
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#1
hi guys, can someone tell me what's the advantages of having a prime lens like EF 50mm. and what does the focal length tells abt the lens, say a 70-200mm f2.8 and a 70-200mm f4. pardon me for being such a newbie here. thanks ;)
 

Jul 22, 2008
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#2
for my question on prime lens, with no zoom. i wonder why some of such lens are more expensive then those 18-35mm lens. TIA again.
 

zac08

Senior Member
Feb 21, 2005
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#3
You really need to read up more on the basics first.

Why a 50mm is favoured is due to the aperture size. The most basic one is already f1.8. And that is more than 1 stop faster than f2.8 of the best zooms.

Both are 70-200, same focal length... ONLY difference is the maximum aperture size.

f2.8 and f4



Really, pls go to the nearest library and take some time to read up... there are some threads here which are pretty informative too.

Photography Notes For Newbies by sulhan
 

lennyl

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Mar 27, 2008
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#4
hi guys, can someone tell me what's the advantages of having a prime lens like EF 50mm. and what does the focal length tells abt the lens, say a 70-200mm f2.8 and a 70-200mm f4. pardon me for being such a newbie here. thanks ;)
Some information to get you started.

Focal length tells you how "close" you can get to a subject, or how wide a view you cal pull in. There are other differences as well - you can't walk closer to a subject with a short lens, and expect to get the same composition, compared to a longer lens.

Advantage of having a prime is that they have simpler optics, so can be sharper and faster. I don't know of any Canon zooms that are faster than f/2.8. On the other hand you can get a 50mm f/1.2 if you're willing to cough up the money. There used to be a 50mm f/1.0 and a f/0.9 I believe.

When we say a lens is "fast", we mean that the aperture is large (which translates into faster shutter speeds, all else being equal). The smaller a number, the larger the aperture (notice that the number is given as "f (focal length) divided by X"). The aperture is the hole in the lens that lets light through the lens.

A good book for introduction to the technology is David Busch's Mastering DSLR. You won't master anything by reading that book (I should know - I have the book) but it gives a pretty good intro. For a good intro book on photography, try Bryan Peterson's Understanding Exposure.
 

lennyl

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Mar 27, 2008
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#5
for my question on prime lens, with no zoom. i wonder why some of such lens are more expensive then those 18-35mm lens. TIA again.
Why is one lens more expensive than another? If you ignore brand differences and market forces, it boils down to:

1. Build / optical quality. Some are plastic. Others are metal. Some use exotic optical glass to correct for abberations. Fluorite, ED, UD, SLD... I found a link here that may be useful in decoding some of these.

2. Auto focus motor. There are cheaper, slower motors and more expensive motors. Some allow you to use manual focus without switching between AF and MF.

3. Design / Others. Does the front element rotate when focusing? Does it extend / retract when focusing? What is the maximum aperture? Diaphragm blades - circular? (affects bokeh - something else for you to google if you're not familiar with it).
 

Jul 22, 2008
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#8
thanks everyone, i really should get some book to digest on. but may i ask another question, what does larger aperture does? image will be sharper or less bokeh or what ? pardon me again.
 

Jul 22, 2008
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#9
thanks Daedalus, the link is useful for me to understand better abt lens.
 

chalib

Senior Member
Oct 4, 2007
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#10
thanks everyone, i really should get some book to digest on. but may i ask another question, what does larger aperture does? image will be sharper or less bokeh or what ? pardon me again.

Bro what mode in your cam when u shoot? When you buy your new cam, did u take the basic photography introduction by the cam manufacturer?

It is very long to explain here if you don't know the basic of photography : Exposure
 

calebk

Senior Member
Jul 25, 2006
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Clementi
#11
thanks everyone, i really should get some book to digest on. but may i ask another question, what does larger aperture does? image will be sharper or less bokeh or what ? pardon me again.
Please refer to the link zac08 posted on basic photography.
 

lennyl

New Member
Mar 27, 2008
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#12
thanks everyone, i really should get some book to digest on. but may i ask another question, what does larger aperture does? image will be sharper or less bokeh or what ? pardon me again.
Large aperture lets in more light, so you can use faster shutter speed.

Large aperture also means shallower depth of field (a narrower depth of the image will be in acceptably sharp focus, with the rest getting more and more blurry the farther they are away from the focus distance). Large aperture = more bokeh (bokeh = out of focus highlights)

Finally, most lenses are sharpest at around f/8 to f/11. They tend to be soft wide open, and when the opening is too narrow, you have diffraction issues (it'll become soft again).

If you search online, you can find some samples of how aperture affects how an image looks. Or you can try the books I mentioned.
 

Rashkae

Senior Member
Nov 28, 2005
19,105
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#13
Large aperture = more bokeh (bokeh = out of focus highlights)
Not really... Bokeh is how out-of-focus highlights are rendered. Unless you're shooting at hyperfocal settings, you'll always get bokeh. :)

But it's fair to say that a larger aperture will give you more OOF backgrounds, thus highlighting a lens' bokeh better.
 

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