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Old Oct 2, 2005, 2:25 PM   #1
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I just ordereda Maxxum 5d butI wanted to order a zoom lens with it too,I originally ordered the Sigma 70-300 APO DG, but (even thou the webpage said it was in stock) the salesperson told me that this lens is on back order, I can't seem to find it anywhere, so my question is, is this lens not out yet ? sigma4less says "To Be Anounced" anyone know about this lens? or have one?

Or any advice on a similar priced lens that will give me good results ( not looking for pro results yet :P )

Thanks

Shanti Castillo G.
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Old Oct 2, 2005, 7:28 PM   #2
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Old Oct 3, 2005, 5:20 PM   #3
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I am looking for a little bit more zoom and the sigma seemed to be a good deal, and i've seen some sample shots and they look great! is there really a big diference in 200 vs 300 ?

while on the subject, does anyone know how to convert lets say 300mm to meters? what i mean by this is how long does 300 reach in meters and still see the details.

as yuou can see,I am new to SLR in general :P


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Old Oct 4, 2005, 7:01 AM   #4
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Remember that with a 5D you get a 1.5 crop factor (as the sensor is 24mm instead of 36mm like the film). So the 300mm lens effectively behaves like a 450mm lens. AS a general rule of thumb, 50mm gives you the angle of view of the human eye, so a picture with a 50mm lens on a 35mm film camera willgive no magnification of the image - it will appear as you see it. 450mm gives youa 9X magnification, so it's going to look a bit like your 10X binoculars. Not sure if this helps.
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Old Oct 4, 2005, 5:18 PM   #5
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i am so confued about the crop factor of 1.5x some people say a 300 lens will work as a 450 lens, but some other say that this is not true, you will see a 300mm image butb croped like a 450, but not magnified.

aquote from another forum

"The sensor in the 5D is smaller than full frame film. It theoretically captures the field of view (FOV) of a longer lens, but not the focal magnification of a longer lens. The image projected from a 17mm lens onto a digital camera sensor is no larger than it is on a film camera. It is a cropped rectangle from the same image that a 35mm film camera would capture at 17mm. The same field of view might be that of what a 28mm lens would capture on film, but it wouldn't have anymore detail or magnification than a 17mm lens could project onto film.

Essentially you get less area coverage and no additional magnification. "

so which is it?

Thanks

Shanti Castillo G.

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Old Oct 4, 2005, 6:43 PM   #6
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Warning -- I wrote a book here (as I often do). I am too long winded sometimes.

Shanti wrote:
Quote:
i am so confued about the crop factor of 1.5x some people say a 300 lens will work as a 450 lens, but some other say that this is not true, you will see a 300mm image butb croped like a 450, but not magnified.
I'm as guilty as anyone in how I explain this, since the "popular" thing to do is call it a crop factor.

Also, you see this type of information being propagated in forums everywhere, by relatively knowledgable individuals.

But, when you think about it, there is no "crop factor" involved here. Remember, you've got lenses designed specifically for a DSLR with an APS-C size sensor, with smaller image circles.

Are you still looking at a cropped view then? Nope.

Do you still need to use a multiplier to see how the angle of view would compare to the same focal length lens on a 35mm camera? Yes.

Look at a camera like the Olympus E-1, or E-300. It's sensor is even smaller than the one in a model like the KM 7D or 5D. Is it a crop? Nope.

How about a model with an even smaller sensor. Let's look at something like my little Konica KD-510z pocket camera. It's lens is marked as 8-24mm. Is it being cropped in some manner to give me the same angle of view I'd have on a 35mm model using a 39-117mm lens? Nope.

The lenses are correctly marked with theactual focal length of the lens (and in the case of fixed lens consumer models, the "35mm equivalent focal range" is also given in their specifications).

What changes is the angle of view, which will depend on the sensor (or film) size, for any given actual focal length.

The mainreason that you see the 35mm equivalent focal lengths of the lenses mentioned, and crop factors/focal length multiplierspublished, is so that users of 35mm cameras have a better idea of how the angle of view compares to the same focal length lens on a 35mm model.

This is only because 35mm cameras are so popular!

Let me repeat that.

This is only because 35mm cameras are so popular!

What compounds the confusion, isthat DSLR bodies are often designed so that a lens from the same manufacturer's 35mm bodies can be used on it. In this case, the image circle is larger than the sensor. That's notwhat makes the angle of view different.

You see the same types of differences when you go to film that's larger than 35mm, too. The actual focal lengths of the lenses are still marked on them. Yet, you'll have a widerangle of view for any given actual focal length compared to a 35mm model (versus a narrower angle of view like you'd have using the same focal length lens on a model with a smaller sensor orfilm size).

For example, a 45mm (actual focal length) lens on a 645 format camera would have a 35mm equivalent focal length of approximiately 29mm. What I mean by that is the angle of view would appear to be the same as a 29mm lens would have on a 35mm camera.

So, if 645 format models were more popular than 35mm cameras, we may be seeing focal length multipliers/crop factors for 35mm cameras (so that users would understand how the angle of viewcompares, when using the same focal length lens on a 35mm camera, that they were accustomed to using on a camera using a larger film size.

If 35mm models weren't so popular, there would be no reason to even mention a "35mm equivalent focal length" or "crop factor".It's done for comparison purposes, since the actual focal lengths of the lenses is are how they are marked.

Does it make any difference that the sensor happens to be smaller than 35mm film for detail purposes? Not if the sensor is capable of capturing what you need, just as if you were comparing 35mm film witha larger film format.

Ditto for things like angle of view or depth of field. Sure there is a difference. That's because of the sensor or film size, and how yourangle of view changes with the film or sensor size,for any given actual focal length lens.

Should we abandon 35mm because 645 is larger, or abandon 645 because I can get an 8x10" camera? LOL

You use works best for you.

Are focal length multipliers/crop factors useful (even if these terms are relatively inaccurate)?

Sure they are.

They help users that are familiar with 35mm cameras determine how a lens at a given focal length compares when using a DSLR that has a sensor size that is smaller, from an angle of view perspective.

Now, just to make things even *more* confusing, the angle of view is often published with lens specifications.

But, the specifications will *assume* that the lens is being used with a given film or sensor size. If you look at a lens with a 45mm focal length designed for a 645 format camera, it's going to show you a wider angle of view than you'll find in the specifications for a 45mm lens used on a 35mm camera.

The lens manufacturers compute the angle of view for the format the lens is designed for.

Interesingly, I'm seeing some lenses designed specifically for DSLR models with sensors smaller than 35mm film, that show an accurate angle of view in their specifications. Nikkor DX lenses are a good example of this.

For example, the widest angle of view for the Nikkor 18-70mm f/3.5-4.5G ID-IF AF-S DX lens is shown as 76 degrees at a focal length of 18mm (as you would expect when a lens with a focal length of 18mm is used on a DSLR model with a smaller sensor).

If you look at a non-DX lens, the angle of view shown in the specifications for a given focal length assumes it will be used on a 35mm model.For example, the Nikkor 18-35mm f/3.5-4.5DED-IF AF lens (non DX lens) shows an angle of view in it's specifications of 100 degrees at a focal lenth of 18mm (as you would expect when an 18mm lens is used on a 35mm camera).

The focal length at the widest setting for both lenses is identical. What changes is the angle of view, depending on the size of the sensor/film the lens is being used with. In the case of Nikkor DX lenses, the manfacturer is just taking the format the lens isbeing used on into consideration when the specifications are published.

You'll see the same thing in specifications for larger format cameras (lenses designed for them show the correct angle of view for the filmformat being used.

I haven't looked at the specs on other "made for digital only" lenses, but you may see the same thing in them, too.

But, most users don't understand angle of view, they understand how a given focal length lens looks from an angle of view perspective when used on a 35mm camera.

Here is a handy online application on Canon's web site that actually shows the angle of view clearly in the graphics:

http://consumer.usa.canon.com/app/ht...al_length.html

But, the angle of view shown is for a given focal length lens when used on a 35mm camera (that's what this application was designed for).

If you were using the samefocal length lens on a model with a larger sensor or film size, you'd have a wider angle of view.

If you were using the same focal length lens on a model with a smaller sensor or film size, you'd have a narrower angle of view.

That's what the so called "crop factors" and "focal length" multipliers are good for -- so that users familiar with using a 35mm camera have a better understanding of how the angle of view compares, for agivenfocal length lens,when it's used on a DSLR with a smaller sensor.


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Old Oct 4, 2005, 8:01 PM   #7
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Thanks for the anwser!I thinkI understand better now

what changes is the angle of view, not the magnification.


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Old Oct 4, 2005, 8:14 PM   #8
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Shanti wrote:
Quote:
Thanks for the anwser!I thinkI understand better now

what changes is the angle of view, not the magnification.

They are related. If you have a narrower angle of view, you'll have more apparent magnification (becauseasubject at a given distance will fill a greater percentage of the frame).

If you have a wider angle of view, you'll have less apparent magnification (because thena subject atgiven distance will filla smaller percentageofthe frame).

The graphics on the Canon web site I posted a link to above for focal length comparisons (based on 35mm models) gives you a better idea of how this works. Select different focal lengthsat the bottom and you can see how everything changes.


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Old Oct 5, 2005, 10:50 AM   #9
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That was a great Explanation there Jim! Thank you, it'll make it easier now to explain that to my wife when she asks about it, when I mention buying a certain type of lens... LOL:-)
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