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Old Apr 6, 2004, 11:13 PM   #1
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I am looking at buying a dSLR, but am still confused about a few things.

1. For starters, about additional lenses, they are typically given a stat like ¨50mm/f1.8¨ what do these values actually mean, and how do they make a lens different from another. I understand the concepts of aperture values, and the basics of focal lengths, but how is it actually related with a particular lens?

2. What actually does a tele converter do? And why do a lot of people seem to shy away from them?

3. Most importantly, it seems the Canon Rebel is the most popular choice for starter SLR photographers, and every review i`ve read has nothing bad to say....though this is great, I do like to see some bad reviews on a product. Nothing is perfect in life, and its nice to know what will annoy you when you finnally choose a product.

Sorry if all my questions are as clear as mud, but would like a little help.

Cheers
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Old Apr 7, 2004, 1:13 AM   #2
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1.
The "f1.8" is the largest aperture that lens is capable of. The larger the aperture, the more light you get (which is great)... but you know that. On larger lenses (not the 50mm), this can lead to heavier & more expensive lenses (because there is more materials.)

The 50mm is a statement of the focal length. In this case, it's a fixed length lens. 70-200 means it is a zoom lens. It goes from a min focal length of 70mm to a max focal length of 200.

Just to make something more complex, you also have lenses like this one:
100-400 f4.5-f5.6
What this means is that the max aperture at 100mm is 4.5, and the max aperture at 400mm is f5.6. You can get lenses that have a constant aperture across the entire zoom range but they are more expensive.

What don't you understand here? Do you not understand what the different focal lengths get you?

2. A teleconverter magnifies the center portion of the image and projects it on to the sensor (or piece of film.) This has the result of making a given lens act like a longer lens. The trade offs are multi fold.

Any imperfections in the lens will be magnified. This means that if you put a teleconverter on a optically less-than-good lens, it will make it look worse. If you use it on a really good lens, it will look a little bit worse. The more lens imperfections that are there, the more that are magnified.

You loose 1 stop of light for a 1.4xTC and 2 stops of light for a 2.0xTC. A f4 lens becomes a longer focal length f5.6 lens. This means that you'll have to use a slower shutter speed to gain back the light lost when using the teleconverter. For some photography this doesn't matter. For some, it prevents it. Action photos with a slower shutter means a blury photo.... this is rarely desirable.

3.
There have been many topics here about the shortcomings of the DRebel. Please go back through the posts here and I'm sure you'll find them. I would not use the DRebel for what I do, but I am very specialized (wildlife, especially birds.) For others, it is just fine (great, even, because the savings over the 10D means they can buy a better lens. And good lenses are a very worthwhile investment.)

I hope that helps. Please feel free to ask more questions, we're a nice bunch here.

Eric
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Old Apr 7, 2004, 11:16 AM   #3
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Thanks you very much for that reply, it for sure clears things up for me 100%!!

Though a bad review would have been nice ;-) will look around a bit more though the posts.

Cheers, Marc
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Old Apr 7, 2004, 11:21 AM   #4
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Eric did a good job to explain and answer your questions, I just have some additional comments:

The 50mm represents the focal length of the lens, 50mm is a standard lens, has the same angle of view like your eyes, the smaller the value of the focal length of the lens, the wide angle of view, such as the 28mm, 24mm, 20mm and to the widest such as the 8mm or 12mm, sometimes they call fisheyes, represent 180 to 360 degree angle of view, the large value represent the telephoto with narrower angle of view, such as the 100mm, 180mm, 200mm, 300mm, 500mm…, which bring the subject closer from a distance.

The F1.8 is the aperture value of the lens or the opening of the lens, the smaller value represents the larger opening of the lens, allow more light to reach the film or the chip for final exposure. The basic of photography is the exposure, which is the combination of the aperture (f-stop) and the shutter speed (time value). Lens with longer focal length and large aperture is very expensive such as the 200mm F/2.8 or 300mm F/2.8, means high speed lenses, allow you to open the opening of the lens at maximum value to shoot with higher speed (faster time). Why is that? Well, here is the basic example:

You have an empty 1 gallon bottle, you want to fill it up with water, you can fill that bottle with water a lot faster if the bottle has larger opening as compare to the one with smaller opening, either way, you will end up with a full gallon of water bottle. In photography, it works in the same concept with exposure, you set the larger aperture (smaller value), then the shutter speed must be faster, same as if you set smaller aperture (larger value), then the shutter speed must be slower to get the correct exposure, the rule of thumb is, if you decrease the value of the aperture by 1 stop, you must increase the value of the time by one stop also. For an example:

Supposedly the correct exposure is recommended by the camera for final exposure is:

F8 @ 1/125

You can change those value as follows to shoot and still have correct exposure:

Decrease the value of the aperture by one stop (open the lens one stop wider), increase the shutter speed by one stop

F5.6 @ 1/250

And so on:

F/4 @ 1/500

The results are you have correct exposure on your final exposure, except, the effect of each photograph will be different, picture with large aperture value will have limited depth of field compare to those pictures which have more DOF with smaller value of aperture setting.

Tele-converter adds more focal length to the lens, a 1.4x at 40% focal length to the lens ex: 100mm with 1.4x equal 140mm lens, or 200mm with 2x converter, but you will loose 1.5 F stops with the 1.4 x and 2 F stops with the 2 x . If you have the 100mm F/2.8 and you add on the 2x converter, you will have equivalent lens of 200 F/5.6. Anytime you put something on front or between the lens and the camera, you tend to degrade the quality of the lens, so be-careful to choose quality product to match the performance of your lens for better result.

The digital Rebel is a good choice of the beginner because it has so many useful features and useful tools and it sold at affordable price. Like you said nothing in life is perfect but human tend to do better. Remember you paid for what you got and there is no free lunch, the Rebel is a great camera but is not quality built compare to the 10D, same as the lens that came with the Rebel kit, does not have the same quality as other better quality zoom lens offers by Canon. But for its price, it is fully justified for what you pay. If you look carefully, you will find down that the Rebel is made in Taiwan and the 10D is made in Japan, you can almost feel the different in quality when you hold them in you hand.

Camera does not make you take better photograph, it helps, but you will...

Cheers
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Old Apr 8, 2004, 1:40 PM   #5
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Cheers again for more info. Do most lenses stop down to f22?

Also i have still yet hold either the rebel or the d10, i understand the build quality is a little less. But when it comes to options and general photo quality is there much of a downside to the rebel? Also the the lens that comes with the rebel might not be top notch, yet you can still buy any lens that you would for the 10d for the rebel, true?
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Old Apr 8, 2004, 1:47 PM   #6
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One more question,does anyone know if Canon is planning to release a newer model of the rebel (or similar priced camera) in the next couple months? ie: is it worth waiting a little longer for a newer and better model (mainly with regards to options). I know i could look at the nikon d70, but i kinda feel better going with a canon.
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Old Apr 8, 2004, 2:36 PM   #7
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I'm also getting ready to join the DSLR ranks from the P&S with the Rebel and have a simple question due to my ignorance! ops:

What does "Bokeh" stand for? I gather it's a statement concerning a lens performance quality that is desirable (like DOF)!?
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Old Apr 8, 2004, 10:07 PM   #8
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Theophile:

Bokeh refers to the blurring of the image outside of the range of focus. Think of the background behind the subject of a portrait. In general the more blades that make up the aperature, the more circular and nicer the bokeh.

It's a subjective thing, you'll like a lens' bokeh or not, it isn't measured like sharpness is.

BTW - you will have bokeh in front of the subject in focus as well as behind. Front bokeh is usually noticeable most often in macro shots where the depth of field is very shallow.

Chappy77 - both your questions have been recently hashed out, look in the forum a bit deeper for the what's next and the 10D vs. 300D debate ranges throughout the forum too.
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Old Apr 8, 2004, 11:23 PM   #9
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Just to answer the specific question. Many, but not all, lenses can stop down to f/22. It is purely an attribute of the lens. The lenses I use most often can, but they are both "L" lenses, which puts them into a different class that the others.

Eric
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Old Apr 9, 2004, 5:31 AM   #10
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Thanks for the Wonderful Explanation Ursa! So would this Capture be a good representation of Foreground and Background "Bokeh"? :roll:

http://community.webshots.com/photo/...31660302pUWbzS

Canon tried to tell me that Bokeh had to do with lens edge sharpness in relation to the center sharpness, but that didn't sound right!!

Much Appreciated!!

Ted
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