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Photography Question 
Allena 
 

First time buyer: What to look for in a lense?


Okay, So I am about to purchase a Canon 30D. I'd just like some input on what I should be looking for in a lense. I've done a good amount of research, but I'd like to get some 'this is what worked for me' advice. My plans are to go into photography professionally. I'm leaning towards portrait, but in the beginning I'll be shooting a lot of candid and landscape I imagine. So I can get used to my camera. Any input would be great. Thanks!


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1/28/2008 1:26:06 PM

 
John P. Sandstedt
BetterPhoto Member Since: 8/8/2001
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  The optimum focal length for portraits is in the 90-105 mm range. But because of the chip dimensions of the 30D, a lens factor of 1.6 imapacts your lens choices.

I have the 17-85 mm IS zoom; it's equivalent focal length range is 28-125 mm, so it straddles the optimum.

I like the lens but it lens is slow.

A lot of folks purchase a 50 mm fixed focal length lens; this gets you to about 85 mm equivalent, and you can get a f/1.4 Canon for under $300.

If your portraiture will include group shots, you might also consider the Canon 17-40 mm f/2,8. It's a bit pricey at $629, by should be well worth the cost.


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1/29/2008 5:54:57 AM

 
Alan N. Marcus   Hi Allena,

When we buy lenses we scrutinize focal length and maximum aperture.

The focal length is important. Technically it’s the distance from about the center of the lens barrel (rear nodal) to the front surface of the sensor chip (image plane or focal plane) as measured when the camera is focused on a distant view. As we focus the camera, the lens mechanically racks in and out. Closer to the chip when focused on a distant scene and further away when focused on close-in object.
This measurement is generally expressed in millimeters. One inch equals 25.4 mm. The focal length is a fundamental optical property of the lens as it expresses the angular field of view (wide – normal – telephoto). The longer the focal length the larger the image however the narrower the angle of view. A 100mm lens yields an image that is twice a big as a 50mm lens.

It is customary to fit a lens with a focal length that is approximately equal to diagonal measure of the rectangular image area (film size or chip size). Your camera has a CMOS sensor (digital chip that replaces film). It measures 15mm by 22.5 thus its diagonal measure is 27mm. If your camera is fitted with a lens about 27mm focal length, the view it sees is said to be normal meaning the angle of view about equals the human experiences which is an angle of about 53°.

If we mount a shorter lens the angle of view increases and the image size decreases. Should we mount a lens about 30% shorter than normal we enter the realm of wide-angle. For this camera that would be about 19mm or shorter. If we mount a lens that is about 270% longer than normal, in this case 73mm or longer, we enter into the dominion of telephoto.

For portraiture, we choose a lens that is 2.5 times the diagonal or a little longer. This is true because such an arrangement reproduces the human face with a prospective that about matches the subjects self image as seen in the make-up mirror or shaving mirror. Thus the ideal portrait lens for this camera is about 68mm or somewhat longer.

Keep in mind that photography is an art form; you are free to choose whatever focal length your heart desires. Anyway the above values are not etched in stone.

Because teachers, books and adviser’s are old hands with the 35mm film camera and because lenses for the 35mm film camera lenses are plentiful, this format is held as a benchmark. The 35mm film frame measures 24mm by 36mm and the diagonal is 43mm. Thus this revered film format is 1.6 times bigger than your image sensor or stated another way your camera needs lenses that are about 63% shorter than those intended for the 35mm format.

Today most use a zoom lens that sports a variable focal length. If we fitted this camera with one zoom lens its zoom range should center up on 27mm.

Aperture is important. It defines how much light the lens can gather. These values are stated using a cryptic number set. The values are 1 – 1.4 – 2 – 2.8 – 4 - 5.6 - 8 -11 – 16 – 22. This is the set but sometimes in-between values are quoted. The max opening lets in lots of light is the smaller number. The minimum opening greatly restricting light is it the bigger number.

You lens will not span this entire set rather it will maybe start at f/2.8 go thru f/22. Small numbers let in lots of light but depth-of-filed in shallow. Larger values have extensive dept-of-field but greatly restrict light passage. Each value is 1.4 times its neighbor going right and 0.707 times it neighbor going left. Each affords a 2x change in light energy falling of the chip. Values going left allows more light to enter the camera. Going right reduces the light level playing of the chip.

Nobody said it’s easy!

Alan Marcus, Anaheim, CA (dispenser of technical gobbledygook)
ammarcus@earthlink.net


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1/29/2008 7:52:24 AM

 
Carlton Ward
BetterPhoto Member Since: 12/13/2005
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  Hi Allena, This will also greatly depend on what you can afford. If $$ is not a problem I would suggest the Canon 24-70mm f/2.8 L & the 70-200mm f/2.8 L IS lenses. I also have the 17-40mm f/4 L and will most likely get the 10-22mm (non-L) soon.
If $$ is a problem I would still highly suggest the 70-200mm f/4 L (non-IS) for under $600. It is a very sharp lens. Read reviews at B&H photo and other sites like Fred Miranda to see what others are saying about a particular lens. The glass is more important than the camera in that it will last for many years to come but in a couple of years the 60D and the 1Ds Mark V will be released.
Its the optics that give you the ability to get the sharpest & most vibrant images possible.


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1/29/2008 2:49:10 PM

 
Allena    Wow, thank you guys. Great input. I appreciate the time every one took.


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1/30/2008 11:59:46 AM

 
R K Stephenson
BetterPhoto Member Since: 10/5/2007
  Hi, Allena,

One other recommendation: depending on the $$ situation, you should seriously consider the EOS 40D rather than the 30D. It's "only" about $300 more than the 30D, body only.

The sensor and auto-focus have been improved and it has that magical sensor cleaner.

Cheers,

RK


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2/1/2008 1:48:39 PM

 
Carlton Ward
BetterPhoto Member Since: 12/13/2005
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  Allena, I just wanted to echo RK's sentiments. The 40D is a big improvement over the 30D. The sensor clean really does work too. The menu is easier and and it performs better at higher ISO settings. A review from a photo magazine stated that it was the 1st "real" improvement for this line since the 10D.


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2/2/2008 9:23:55 AM

 
Allena    After much deliberation, I was all set on the 30D.
haha So much for that now... Again, thank you for the input. I have some mulling over to do...

-A.B.


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2/2/2008 11:39:12 AM

 
John G. Clifford Jr
BetterPhoto Member Since: 8/18/2005
  Quality is all in a lens. In fact, I'd argue that whether you get a 30D or a 40D (or even use a 20D), the biggest determinant of image quality will be the lens.

A very good, versatile, 'first' lens for such a camera is the Sigma 18-50/2.8 EX Macro. I have several shots in my gallery taken with the lens. It is EXTREMELY sharp, and will outresolve your camera's sensor. Pair it up with the Sigma 50-150/2.8 EX APO and you have two lenses that will fit along with your camera body in a small camera bag, yet will give you the image quality and versatility to work for 99% of all possible photographic situations.


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2/2/2008 6:13:50 PM

 
Allena    Thanks, John. That was really useful input.

-A.B.


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2/9/2008 3:47:54 PM

 
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