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Lense Questions from a beginner
Hi folks,.

I recently purchased a 40D kit with a 28-135 3.5/5.6 lense..

Can someone refer me to a good write-up on the basics of lenses?.

Some questions I have -.

If this lense goes from 28 up to 135 zoom, why would I need a 50mm lense? (Someone suggested I need one.).

Is 3.5 the f-stop? If so are there only 2 fstops? 3.5 and 5.6? (not variable between the two like zoom?) Does that mean that the other camera aperatures dont work when I use this lense?.

Why would it be valuable to have a 17-85 f4/5.6 instead? (since my lense can go down to 28mm, I'm only missing 11mm then right?) Why would lenses overlap like this? Why not just one huge range then just use one lense?etc....

THanks!..

Comments (13)

Bagsjr wrote:.

Cannot help with a general write up. The correct spelling is lens by the way..

Some questions I have -If this lense goes from 28 up to 135 zoom, why would I need a 50mmlense? (Someone suggested I need one.).

That someone is suggesting you buy a 50mm prime (non-zoom) lens. The advantage would be that such lens is lkely to be f/1.4 or f/1.8 wide open and so will allow you to shoot in very poor light..

Is 3.5 the f-stop? If so are there only 2 fstops? 3.5 and 5.6? (notvariable between the two like zoom?) Does that mean that the othercamera aperatures dont work when I use this lense?.

Your lens has a MINIMUM aperture of f/3.5 at 28mm to f/5.6 at 135. The maximum aperture will probably be f/22 at both ends of the zoom range and all points in between..

Why would it be valuable to have a 17-85 f4/5.6 instead? (since mylense can go down to 28mm, I'm only missing 11mm then right?).

That 11mm covers wide-angle to mid-range focal lengths on your SLR..

Why would lenses overlap like this? Why not just one huge range then justuse one lense?.

All lenses are a compromise between optical quality (chromatic abberation, sharpness, contrast etc), low light ability (is it a "fast" lens?), size, weight build quality and price..

Chris Elliott.

*Nikon* D Eighty + Fifty - Other equipment in Profile.

Http://PlacidoD.Zenfolio.com/..

Comment #1

Bagsjr wrote:.

Hi folks,.

I recently purchased a 40D kit with a 28-135 3.5/5.6 lense..

Can someone refer me to a good write-up on the basics of lenses?.

Try the Glossary section of this site for a start..

Some questions I have -If this lense goes from 28 up to 135 zoom, why would I need a 50mmlense? (Someone suggested I need one.).

Because the Canon 50mm f1.8 prime lens is cheap, is better optically than the 28-135mm and is much "faster", i.e. it has a much larger maximum aperture and can be used in much lower light. However, I wouldn't make this lens a priority - wait until you think that need it. I don't use mine very often..

Is 3.5 the f-stop? If so are there only 2 fstops? 3.5 and 5.6? (notvariable between the two like zoom?) Does that mean that the othercamera aperatures dont work when I use this lense?.

F3.5 is the maximum aperture at 28mm, which then decreases gradually to f5.6 at 135mm (a larger f number is a smaller aperture and therefore less light gets through the lens). There is no maximum aperture, although image quality will start to deteriorate due to diffraction above about f16 or f22..

Why would it be valuable to have a 17-85 f4/5.6 instead? (since mylense can go down to 28mm, I'm only missing 11mm then right?) Whywould lenses overlap like this? Why not just one huge range then justuse one lense?.

The 28-135 is a very good lens (I have used one). However, it is designed for a film camera or a full frame digital camera like the Canon 5D or D1s. On a 1.6 crop factor like the 40D the effective focal length is 45-216mm which isn't really wide enough for a general purpose lens, and the loss of wide angle is much more important than the additional zoom..

Canon developed the 17-85mm lens (which I have) to be exactly the equivalent on a 1.6 crop factor camera as the 28-185 on a full frame/film camera. That is why the two lenses exist. You wouldn't normally own both..

I recommend keeping the 28-135mm and see how you like it. It is better optically than the 17-85mm but the IS is a bit slow. I have a friend who uses the 28-135mm as his principal lens on a 1.6 crop factor Canon. If you think that you want something wider you can always buy a specialist wide angle lens. If you every move up to a 5D you can use the 28-135mm but not the 17-85mm..

Lenses with really long zoom ranges are of lower optical quality, especially at the two extremes. That is why almost all professional zooms have 3x zoom or less, e.g. 24-70, 70-200, etc..

I hope that this is useful..

Chris R..

Comment #2

Some questions I have -If this lense goes from 28 up to 135 zoom, why would I need a 50mmlense? (Someone suggested I need one.).

A fixed focal length (non-zoom) 50mm lens will have a much wider maximum aperture like f/1.8. Such lenses are excellent for use in low light, like indoors without a flash. You don't *need* one since your lens already includes 50mm, and you can always use the flash if it is dim. But if you prefer not to use the flash, a 50mm f/1.8 is a great indoor lens..

Is 3.5 the f-stop? If so are there only 2 fstops? 3.5 and 5.6? (notvariable between the two like zoom?) Does that mean that the othercamera aperatures dont work when I use this lense?.

F/3.5 is the maximum f-stop (aperture), corresponding to the widest hole, letting in the most light. As you zoom in the maximum aperture decreases to f/5.6. Basically, as you magnify the image more, it gets dimmer, because the same amount of light is being spread out more. You *can* get fixed-aperture zooms which stay at (for example) f/4 right across the range, but they are much more expensive, and bigger and heavier. Having a smaller maximum aperture as you zoom in more is the price you pay for a light, affordable zoom lens..

There is a wide range of f-stops starting from the maximum (which is between f/3.5 and f/5.6 depending where you are in the zoom range) down to about f/22 (a small pinhole sized opening). It is the widest aperture that is quoted in the lens specifications as that is the one of most interest. (An analogy: if a car is quoted as having a top speed of 150 mph, that doesn't mean that it only does 150 mph!).

Why would it be valuable to have a 17-85 f4/5.6 instead? (since mylense can go down to 28mm, I'm only missing 11mm then right?) Whywould lenses overlap like this? Why not just one huge range then justuse one lense?.

Your lens is a slightly odd range for a DSLR: it doesn't have much of a wide angle end. 28mm will give you a field of view only a little wider than the human eye. 135mm is quite a powerful telephoto. Wide angles are very useful for general-purpose shooting (groups of people; buildings; landscapes...) and the standard 'kit' lenses on most DSLRs are something like 18-55 or 18-70mm range, with 18mm giving a reasonable wide angle view..

A 17-85 would make an excellent standard lens for your camera, covering a useful range from wide angle to modest telephoto. but as you say there is a lot of overlap with the 28-135 you already have. If you have the choice, get a 17-85 instead of a 28-135, definitely..

Although the difference between 17 and 28 is 'only' 11mm, it is the ratio that counts (nearly 2:1). The difference in coverage between 15mm and 30mm is the same as the difference between 100mm and 200mm..

You can get very wide range 'superzooms' like the Tamron 18-250 which covers pretty much everything you will need on one lens. The trade-off is slightly poorer optical quality than you get in shorter-range zoom lenses. if you are only making prints at 4 x 6 or 5 x 7 inches for the family album, an 18-250 would be great and mean you would never have to change lenses. if you want to make 20 x 16 prints to exhibit you would porbably want higher optical quality..

Best wishesMike..

Comment #3

Do what I did to start... get any photography book that covers the basics because if you're anything like me, stuff won't stick unless you read it several times over (especially when you're first starting out). At this point, any basics book will do. These books will cover questions like the ones you posted and then some..

Also, don't make the same mistake I made and get too tangled up on the technical stuff (although it will prove important later). Go out and take pictures and you'll begin to see the limitations of the lenses you have and then some of this stuff will make sense...Hope this helps.Corona_Drinker..

Comment #4

Here is a quick post I wrote up about choosing a lens and a link to a really great source on just this question. Hope it helps!.

Http://www.b3nbrooks.com/blog/?p=92.

Benhttp://www.b3nbrooks.com/blog/ - for my pics...

Comment #5

Thanks everyone. Great information. I might go but a 50mm for indoors to practice with...

Comment #6

Try the glossary on this site..

Http://www.dpreview.com/learn/?/Glossary/Exposure/Aperture_01.htm.

How refreshing. It must be all of 48 hours since this question was last asked!:.

Http://forums.dpreview.com/...ums/readflat.asp?forum=1002&thread=26277016.

I used to to think this site has a vested interest in not providing a FAQ. It keeps the number of clicks up. But now I begin to suspect that nobody would read it anyway just like nobody does a search or reads the glossary..

Chris Elliott.

*Nikon* D Eighty + Fifty - Other equipment in Profile.

Http://PlacidoD.Zenfolio.com/..

Comment #7

Chris Elliott wrote:.

Your lens has a MINIMUM aperture of f/3.5 at 28mm to f/5.6 at 135.The maximum aperture will probably be f/22 at both ends of the zoomrange and all points in between..

Oh, Chris! Shame on you! It is the other way round! .

The lens's MAXIMUM aperture is the LOWEST f/number. That's where the aperture (hole) is biggest and admits most light... in this case f/3.5 at the 28mm f-length, and f/5.6 at 135mm f-length..

The lens's MINIMUM aperture is the HIGHEST f/number. In this case all f-lengths stop down to a minimum of f/22, it seems.Regards,Baz..

Comment #8

Barrie Davis wrote:.

Chris Elliott wrote:.

Your lens has a MINIMUM aperture of f/3.5 at 28mm to f/5.6 at 135.The maximum aperture will probably be f/22 at both ends of the zoomrange and all points in between..

Oh, Chris! Shame on you! It is the other way round! .

The lens's MAXIMUM aperture is the LOWEST f/number. That's where theaperture (hole) is biggest and admits most light... in this casef/3.5 at the 28mm f-length, and f/5.6 at 135mm f-length..

The lens's MINIMUM aperture is the HIGHEST f/number. In this case allf-lengths stop down to a minimum of f/22, it seems..

Barrie,.

Yes I should have said minimum aperture number to make things quite clear. If I had said maximum aperture on it's own that would give the impression that the minimum was something like f/1.4. Having typed the same thing so many times I was sort of in autopilot..

Chris Elliott.

*Nikon* D Eighty + Fifty - Other equipment in Profile.

Http://PlacidoD.Zenfolio.com/..

Comment #9

Chris Elliott wrote:.

Barrie,.

Yes I should have said minimum aperture number to make things quiteclear. If I had said maximum aperture on it's own that would give theimpression that the minimum was something like f/1.4. Having typedthe same thing so many times I was sort of in autopilot..

Yes. No sweat. I suspected it was just an 'error of the moment.' .

Regards,Baz..

Comment #10

Bagsjr wrote:.

Hi folks,.

I recently purchased a 40D kit with a 28-135 3.5/5.6 lense..

Can someone refer me to a good write-up on the basics of lenses?.

Some questions I have -If this lense goes from 28 up to 135 zoom, why would I need a 50mmlense? (Someone suggested I need one.)Is 3.5 the f-stop? If so are there only 2 fstops? 3.5 and 5.6? (notvariable between the two like zoom?) Does that mean that the othercamera aperatures dont work when I use this lense?Why would it be valuable to have a 17-85 f4/5.6 instead? (since mylense can go down to 28mm, I'm only missing 11mm then right?) Whywould lenses overlap like this? Why not just one huge range then justuse one lense?etc....

THanks!.

- You're joking, right?.

Http://lordofthelens.smugmug.com/..

Comment #11

Uh no I wasn't but I think I understand lenses now at least a bit. Read everything I could.

I gotta fast 70-200 for the dobie shows. Canon EF 70-200mm f/2.8L .

It's a nice lens..

Thanks,Bob...

Comment #12

MICHAEL_61 wrote:.

Bagsjr wrote:.

Hi folks,.

I recently purchased a 40D kit with a 28-135 3.5/5.6 lense..

Can someone refer me to a good write-up on the basics of lenses?.

Some questions I have -If this lense goes from 28 up to 135 zoom, why would I need a 50mmlense? (Someone suggested I need one.)Is 3.5 the f-stop? If so are there only 2 fstops? 3.5 and 5.6? (notvariable between the two like zoom?) Does that mean that the othercamera aperatures dont work when I use this lense?Why would it be valuable to have a 17-85 f4/5.6 instead? (since mylense can go down to 28mm, I'm only missing 11mm then right?) Whywould lenses overlap like this? Why not just one huge range then justuse one lense?etc....

THanks!.

- You're joking, right?.

This is the Beginners Questions Forum, Michael. Many of us do not have the entire spectrum of photographic knowledge in our memories..

The question is reasonable, and the OP is willing to be better informed..

Leonard Migliore..

Comment #13

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This question was taken from a support group/message board and re-posted here so others can learn from it.

 

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