I was reading over an issue of Popular Photography and had a question about a lens I saw and lenses in general.

In the magazine there's an ad for a lens. It's described as a 100MM F2.8 lens.

Now, I thought F2.8 had to do with apeture. 2.8 being pretty wide open. However, as I look closer at the lens, I see various settings for apeture. Starting at 2.8 and going up in this order:

2.8
4
5.6
8
11
16
22
32

Now I know this is a stupid question, but I thought the F2.8 meant the only apeture the lens could do is 2.8? How come there's an additional 8 other settings on the lens?

Try not to laugh too  hard...we were all newbies once

That is the lowest it's capable of (largest opening).  That is the limitation of design and cost, usually.  The lower the min f/stop is the more light gets in and the more flexible the lens is to use (for isolation subject against a blurry background or shooting in low light).  I think.

The lower the aperature number, the more light that passes through the glass.

Lenses can only let in a certain amount of light, but the aperature can be contrained to allow for less light (but much sharper images).

A F2.8 is good for moving shots at 100MM.

A F1.0 would be 100% light throughput (and hence very expensive and somewhat rare to find).

The 50mm lenses are usually the exception when it comes to price for lowest (largest) aperature.

Quoted: Quoted: I was reading over an issue of Popular Photography and had a question about a lens I saw and lenses in general. In the magazine there's an ad for a lens. It's described as a 100MM F2.8 lens. Now, I thought F2.8 had to do with apeture. 2.8 being pretty wide open. However, as I look closer at the lens, I see various settings for apeture. Starting at 2.8 and going up in this order: 2.8 4 5.6 8 11 16 22 32 Now I know this is a stupid question, but I thought the F2.8 meant the only apeture the lens could do is 2.8? How come there's an additional 8 other settings on the lens? Try not to laugh too  hard...we were all newbies once it means the max aperture is 2.8 which is really wide.

So what does it mean if a lens says it is F/3.5-5.6?

What's the significance of the hyphen to another apeture?

you need to be able to set the aperature so there is always a range... there are a number of reasons for this.

1. do play with focal lenght.. the larger the aperature the smaller the focal plane and vice versa.. this is how portraits have blurry backgrounds, and landscapes are clear througout.

2.  if its really bright out you use it to gain proper shutter speed.. for example on a really bright day and camera at f/2.8 it might want to use a shutter speed of 1/4000sec.. but say the camera doesnt do this... so it will make the aperature smaller say f/8 and that allows for the shutter speed to be slower such as 1/1500sec.  it goes the other way as well.. action shots or stop action shots require a faster shutter speed which proper exposure is attained by opening up the aperature all the way.

Different aperatures at the extremes of the zoom.  It's variable in some zoom lenses depending on where you have it in the zoom range...

Quoted: So what does it mean if a lens says it is F/3.5-5.6? What's the significance of the hyphen to another apeture?

Means it is variable in the lowest it will go.

This is found with zoom lenses where the forward glass is moving creating a space where light will be lost.

The aperature can't get any smaller but the glass moves farther forward constraining light.

If the lense is a 35 - 135 F3.5 - 5.6 it means at 35MM the F is 3.5 but at 135 the F is 5.6.

Quoted: So what does it mean if a lens says it is F/3.5-5.6? What's the significance of the hyphen to another apeture?

its capable of a maximum f/3.5 when camera is zoomed all the way out, and capable of a maximum f/5.6 when the camera is zoomed all the way in.

Quoted: Quoted: Quoted: Quoted: I was reading over an issue of Popular Photography and had a question about a lens I saw and lenses in general. In the magazine there's an ad for a lens. It's described as a 100MM F2.8 lens. Now, I thought F2.8 had to do with apeture. 2.8 being pretty wide open. However, as I look closer at the lens, I see various settings for apeture. Starting at 2.8 and going up in this order: 2.8 4 5.6 8 11 16 22 32 Now I know this is a stupid question, but I thought the F2.8 meant the only apeture the lens could do is 2.8? How come there's an additional 8 other settings on the lens? Try not to laugh too  hard...we were all newbies once it means the max aperture is 2.8 which is really wide. So what does it mean if a lens says it is F/3.5-5.6? What's the significance of the hyphen to another apeture? I edited my first post to explain that, but you had already quoted my original one:P

Okay, I think I know what you're talking about now.

So for example, I'm looking at an ad for a Sigma 28-135mm f/3.8-5.6.

This means the max apeture is 3.8 when at 28MM and when maxed at 135MM it's 5.6?

Conversely, there's another Sigma lens here: 70-200mm f/2.8. This means it can do 2.8 throughout the entire spectrum? That must be why it's an $850 lens compared to the $160 28-135, right?

Quoted: Quoted: Different aperatures at the extremes of the zoom.  It's variable in some zoom lenses depending on where you have it in the zoom range... Yup.   A F3.5-5.6 with a, say 70-200 zoom, would have a max aperture of 3.5 at 70 and a max of 5.6 at 200.

I spelled aperture wrong.

Quoted: Quoted: Quoted: Quoted: Quoted: I was reading over an issue of Popular Photography and had a question about a lens I saw and lenses in general. In the magazine there's an ad for a lens. It's described as a 100MM F2.8 lens. Now, I thought F2.8 had to do with apeture. 2.8 being pretty wide open. However, as I look closer at the lens, I see various settings for apeture. Starting at 2.8 and going up in this order: 2.8 4 5.6 8 11 16 22 32 Now I know this is a stupid question, but I thought the F2.8 meant the only apeture the lens could do is 2.8? How come there's an additional 8 other settings on the lens? Try not to laugh too  hard...we were all newbies once it means the max aperture is 2.8 which is really wide. So what does it mean if a lens says it is F/3.5-5.6? What's the significance of the hyphen to another apeture? I edited my first post to explain that, but you had already quoted my original one:P Okay, I think I know what you're talking about now. So for example, I'm looking at an ad for a Sigma 28-135mm f/3.8-5.6. This means the max apeture is 3.8 when at 28MM and when maxed at 135MM it's 5.6? Conversely, there's another Sigma lens here: 70-200mm f/2.8. This means it can do 2.8 throughout the entire spectrum? That must be why it's an $850 lens compared to the $160 28-135, right?

Now you are getting it.  There is a reason that expensive lenses are expensive.  There WILL be a significant difference in quality of images made with more expensive lenses vs/ cheaper ones, but only you can decide if it's worth the extra money to you based on what you plan on doing with it.  Printing out 4X6 prints uncropped is different than enlargements or wanting to crop a larger photo to a smaller one...

So, as far as applying what I've learned to shooting:

If you have a cheaper 70-200mm lens that has a max apeture of 5.6 at it's peak, it wouldn't be very effective at shooting action or sports shots because it wouldn't let enough light in to be fast enough to capture an action shot? While a more expensive 70-200 that could do 2.8 throughout the length would be fine because of its ability to shoot at 2.8 at 200mm?

Quoted: So, as far as applying what I've learned to shooting: If you have a cheaper 70-200mm lens that has a max apeture of 5.6 at it's peak, it wouldn't be very effective at shooting action or sports shots because it wouldn't let enough light in to be fast enough to capture an action shot? While a more expensive 70-200 that could do 2.8 throughout the length would be fine because of its ability to shoot at 2.8 at 200mm?

all depends on how much light you got.

and that is not a "MAX" max, its the max min.. lol it will still give you f5.6 thru f32 instead of f3.8-f22  its just the maximum bottom number.

Quoted: So, as far as applying what I've learned to shooting: If you have a cheaper 70-200mm lens that has a max apeture of 5.6 at it's peak, it wouldn't be very effective at shooting action or sports shots because it wouldn't let enough light in to be fast enough to capture an action shot? While a more expensive 70-200 that could do 2.8 throughout the length would be fine because of its ability to shoot at 2.8 at 200mm?

I guess it depends on how much light you have, indoor or outdoor, etc.  I think you might be fine with the f/5.6, but I doubt it would ever look like a Sports Illustrated shot with subject very sharp against a nicely blurred background.  I could be wrong.  Check out this site if you want to learn about shooting sports:

Link

Quoted: Quoted: So, as far as applying what I've learned to shooting: If you have a cheaper 70-200mm lens that has a max apeture of 5.6 at it's peak, it wouldn't be very effective at shooting action or sports shots because it wouldn't let enough light in to be fast enough to capture an action shot? While a more expensive 70-200 that could do 2.8 throughout the length would be fine because of its ability to shoot at 2.8 at 200mm? all depends on how much light you got. and that is not a "MAX" max, its the max min.. lol it will still give you f5.6 thru f32 instead of f3.8-f22  its just the maximum bottom number.

So one can count on most lenses (cheap or expensive) at least having a range from f22 or downward a bit to it's listed maximum apeture?

Quoted: Quoted: Quoted: So, as far as applying what I've learned to shooting: If you have a cheaper 70-200mm lens that has a max apeture of 5.6 at it's peak, it wouldn't be very effective at shooting action or sports shots because it wouldn't let enough light in to be fast enough to capture an action shot? While a more expensive 70-200 that could do 2.8 throughout the length would be fine because of its ability to shoot at 2.8 at 200mm? all depends on how much light you got. and that is not a "MAX" max, its the max min.. lol it will still give you f5.6 thru f32 instead of f3.8-f22  its just the maximum bottom number. So one can count on most lenses (cheap or expensive) at least having a range from f22 or downward a bit to it's listed maximum apeture?

yup.

Quoted: Quoted: So, as far as applying what I've learned to shooting: If you have a cheaper 70-200mm lens that has a max apeture of 5.6 at it's peak, it wouldn't be very effective at shooting action or sports shots because it wouldn't let enough light in to be fast enough to capture an action shot? While a more expensive 70-200 that could do 2.8 throughout the length would be fine because of its ability to shoot at 2.8 at 200mm? I guess it depends on how much light you have, indoor or outdoor, etc.  I think you might be fine with the f/5.6, but I doubt it would ever look like a Sports Illustrated shot with subject very sharp against a nicely blurred background.  I could be wrong.  Check out this site if you want to learn about shooting sports: Link

As you mention the blurred background, I realized I had completely forgot to think about depth of field.

Besides letting in more light for action shots, a constant 2.8 lens would be better for portraits, where the subject is sharp and in focus against a nicely blurred background, right?

As you move upward in the apetures, more comes into focus, which makes it better for landscapes. But with closing the apeture, you need longer shutter speed, right?

The more light you let in (smaller aperture number, larger lens opening), the less shutter time you need for and equal amount of light.  Also, as you increase aperture (smaller number) you decrease depth of field, like you said.  You have it right, yes...

Quoted: The more light you let in (smaller aperture number, larger lens opening), the less shutter time you need for and equal amount of light.  Also, as you increase aperture (smaller number) you decrease depth of field, like you said.  You have it right, yes...

Yipee! Thanks for the help everyone!

Now...all I need to do is man up and drop the $1,500+ on a DSLR and lens

Also, a constant 2.8 lense is most liekly going to be quite a bit larger and heavier than a less expensive one.  That is something to consider.  You get more flexibility and better quality, but you pay for it in lens size and in money.

they will both do it... the f2.8 just does it better.. you can also be further away.  the further away the subject in focus is the larger the depth of field...

the aperature is not the only selling point in the f2.8 70-200.. it also has better glass elements and usually better/more element coatings... but if you are just getting into it.. the lower cost lens aint a bad place to start.  Its the indian not the arrow.(to a point)

Quoted: Quoted: The more light you let in (smaller aperture number, larger lens opening), the less shutter time you need for and equal amount of light.  Also, as you increase aperture (smaller number) you decrease depth of field, like you said.  You have it right, yes... Yipee! Thanks for the help everyone! Now...all I need to do is man up and drop the $1,500+ on a DSLR and lens

If you like photography, I think it is money well spent.  You get more freedom to experiment with DSLRs than film, due to the fact that it doesn't cost more to shoot more.  But you might also find yourself relying on that fact instead of trying to take better photos in one or two shots.  Overall, I think it's very worth it, but also realize you will be your own photolab, and should probably plan on buying Adobe Photoshop, or at a minimum Photoshop Elements.

I would like to point out that Mirror lenses are a single f stop rating usually f8.

To reduce the amount of light you remove the lense and screw on neutral density filters on the back side of the lense.



zoom zoom

oh yeah.. the 70-200 f2.8 is going to be about 2x the size and weight 3x as much as the basic lens.

the lens on the left is 80-200 f/2.8  the lens on the right is a 75-300 f/3.5-5.6

Also, check around for a local school that offers adult/evening classes and take a photo class (if you haven't already), you will learn a lot of the basics, at least.

Quoted: Quoted: Quoted: The more light you let in (smaller aperture number, larger lens opening), the less shutter time you need for and equal amount of light.  Also, as you increase aperture (smaller number) you decrease depth of field, like you said.  You have it right, yes... Yipee! Thanks for the help everyone! Now...all I need to do is man up and drop the $1,500+ on a DSLR and lens If you like photography, I think it is money well spent.  You get more freedom to experiment with DSLRs than film, due to the fact that it doesn't cost more to shoot more.  But you might also find yourself relying on that fact instead of trying to take better photos in one or two shots.  Overall, I think it's very worth it, but also realize you will be your own photolab, and should probably plan on buying Adobe Photoshop, or at a minimum Photoshop Elements.

I've got Photoshop 7 already on my computer .


Now....here's another question: ISO.

It's the digital equivalent of ASA for regular film, right? And has to do with sensitivity to light. I'm taking a shot in the dark here, but a high ISO means it's much more sensitive to light (better for night shots and shooting the stars) but can get excessively grainy the higher you go?

Quoted: Quoted: Quoted: Quoted: The more light you let in (smaller aperture number, larger lens opening), the less shutter time you need for and equal amount of light.  Also, as you increase aperture (smaller number) you decrease depth of field, like you said.  You have it right, yes... Yipee! Thanks for the help everyone! Now...all I need to do is man up and drop the $1,500+ on a DSLR and lens If you like photography, I think it is money well spent.  You get more freedom to experiment with DSLRs than film, due to the fact that it doesn't cost more to shoot more.  But you might also find yourself relying on that fact instead of trying to take better photos in one or two shots.  Overall, I think it's very worth it, but also realize you will be your own photolab, and should probably plan on buying Adobe Photoshop, or at a minimum Photoshop Elements. I've got Photoshop 7 already on my computer . Now....here's another question: ISO. It's the digital equivalent of ASA for regular film, right? And has to do with sensitivity to light. I'm taking a shot in the dark here, but a high ISO means it's much more sensitive to light (better for night shots and shooting the stars) but can get excessively grainy the higher you go?

yes.  that is where canon comes in.. CMOS sensors have less noise than equivalent CCD sensors at the higher ISO.

Quoted: Also, check around for a local school that offers adult/evening classes and take a photo class (if you haven't already), you will learn a lot of the basics, at least.

I took photography with a regular old film SLR back in high school, but truth-be-told didn't pay much attention. My technique was to adjust apeture just so I could keep using the same shutter speed (1/125 was always my favorite for some reason) without having to keep adjusting it.

By some miracle I managed to take a shot my teacher always loved. A student was sitting in class studying, as a ray of sun came in from right to left diagonally and cast over his work perfectly. Using my "1/125 technique" I ended up taking a great portrait with a nice blurry background and sharp subject

Quoted: Quoted: Quoted: Quoted: Quoted: The more light you let in (smaller aperture number, larger lens opening), the less shutter time you need for and equal amount of light.  Also, as you increase aperture (smaller number) you decrease depth of field, like you said.  You have it right, yes... Yipee! Thanks for the help everyone! Now...all I need to do is man up and drop the $1,500+ on a DSLR and lens If you like photography, I think it is money well spent.  You get more freedom to experiment with DSLRs than film, due to the fact that it doesn't cost more to shoot more.  But you might also find yourself relying on that fact instead of trying to take better photos in one or two shots.  Overall, I think it's very worth it, but also realize you will be your own photolab, and should probably plan on buying Adobe Photoshop, or at a minimum Photoshop Elements. I've got Photoshop 7 already on my computer . Now....here's another question: ISO. It's the digital equivalent of ASA for regular film, right? And has to do with sensitivity to light. I'm taking a shot in the dark here, but a high ISO means it's much more sensitive to light (better for night shots and shooting the stars) but can get excessively grainy the higher you go? yes.  that is where canon comes in.. CMOS sensors have less noise than equivalent CCD sensors at the higher ISO.

This is because a CCD sensor like on a Nikon has multiple plates, while a CMOS is a single plate sensor, right?

Quoted: Quoted: Quoted: Quoted: Quoted: Quoted: The more light you let in (smaller aperture number, larger lens opening), the less shutter time you need for and equal amount of light.  Also, as you increase aperture (smaller number) you decrease depth of field, like you said.  You have it right, yes... Yipee! Thanks for the help everyone! Now...all I need to do is man up and drop the $1,500+ on a DSLR and lens If you like photography, I think it is money well spent.  You get more freedom to experiment with DSLRs than film, due to the fact that it doesn't cost more to shoot more.  But you might also find yourself relying on that fact instead of trying to take better photos in one or two shots.  Overall, I think it's very worth it, but also realize you will be your own photolab, and should probably plan on buying Adobe Photoshop, or at a minimum Photoshop Elements. I've got Photoshop 7 already on my computer . Now....here's another question: ISO. It's the digital equivalent of ASA for regular film, right? And has to do with sensitivity to light. I'm taking a shot in the dark here, but a high ISO means it's much more sensitive to light (better for night shots and shooting the stars) but can get excessively grainy the higher you go? yes.  that is where canon comes in.. CMOS sensors have less noise than equivalent CCD sensors at the higher ISO. This is because a CCD sensor like on a Nikon has multiple plates, while a CMOS is a single plate sensor, right?

that i dont know anymore..  in truth.. both make great cameras, and both take great photos... and unless you plan on needing iso800 or more on a regular basis.. its personal preference.  I take lots of photos in dark places.. i need the high iso performance.. that is the main reason i went with canon.  my iso 1600 photos look better than iso 400 photos from ccd based cameras.

Don't be overwhelmed by specs, concentrate on getting the fundamentals down, things like using a tripod, composition etc.

Both Nikon & Canon make good cameras, opting for one over the other will neither make you a fine nor a terrible photographer, understanding the basics will (at least get you on your way)

There are some good third party (Tokina, Tamron, Sigma) lenses that can help a starter on a budget, and there are some fine OEM lenses that, with the proper technique, yield superior images, at a cost.

One reference source I find useful

Check out photo.net also.  Lots of good info there.

Thanks Merrell and jvic. I'll check those sites out.

I've been reading at www.slrlearningcenter.com for a while, but will give those ones a shot.

i always explain it like the gauge of a shotgun, smaller number=bigger hole.  that is the largest possible aperture of the lens, and the variable diaphragm within the lens will decrease the amount of light through the range printed on the aperture ring--usually f/32.

Quoted: Quoted: So, as far as applying what I've learned to shooting: If you have a cheaper 70-200mm lens that has a max apeture of 5.6 at it's peak, it wouldn't be very effective at shooting action or sports shots because it wouldn't let enough light in to be fast enough to capture an action shot? While a more expensive 70-200 that could do 2.8 throughout the length would be fine because of its ability to shoot at 2.8 at 200mm? I guess it depends on how much light you have, indoor or outdoor, etc.  I think you might be fine with the f/5.6, but I doubt it would ever look like a Sports Illustrated shot with subject very sharp against a nicely blurred background.  I could be wrong.  Check out this site if you want to learn about shooting sports: Link

here are a couple of things to consider:

the sunny /16 rule:  on a sunny day, shooting e.i.100, correct exposure will be 1/60th of a sec at f/16.  if your max aperture is 5.6, you'll be shooting at 1/500th.  this is fast enough for  people sports, but not enough for motor sports, etc.  to shoot these, you'd need to back off your focal length enough to get to f/4, or move to faster film, which is my preference.  

constant aperture is your friend:  you are right--a constant 2.8 is going to be a more effective piece of glass.  we're talking 2 full stops at max focal length, which is the difference between shooting at 1/250th and 1/1000th.  remember, each stop of aperture or shutter speed cuts the amount of light in half.

now, as for the "SI look", you have to appreciate what factors play into it.  jvic mantioned one--depth of field.  the simplest way to improve the look of your photography is to limit the DOF--sharp subject with blurry background.  

3 factors control depth of field  

1-focal length.  the longer the lens, the smaller the depth of field.
2-aperture.  the wider the aperture, the smaller the depth of field.
3-point of focus.  the closer to your subject you are, the smaller the depth of field.

so the quick and dirty method is to shoot as long as possible, as wide open as possible, and as close to your subject as possible.

now, not to sound too cantankerous, but i've taught photography for too long not to include this little tidbit.  the absence of limitation is the enemy of art!--orson wells.  i made my living with a 50, a 43-86 zoom, and a 135, not because i wanted to, but because it was all i could afford at the beginning.  the result of this was that i had to learn to use each lens properly.  instead of hiding behind gear, i had to learn how to be a better photographer.  so when i finally had enough to afford the luxury glass, i could make the most of it.

i say that to say this:  if you're trying to decide whether to buy a cheaper zoom now, or to wait and buy a fancier one later, by all means buy the slow one now, and use it to become better.  as you work around the limitations of a slower lens, you'll develop techniques that you never would have considered if not forced into it.  you'll broaden your means of expression, and you'll become a far better photographer for it.

best of luck to you, and post some pics.






[edit:  tags]

Quoted: i always explain it like the gauge of a shotgun, smaller number=bigger hole.  that is the largest possible aperture of the lens, and the variable diaphragm within the lens will decrease the amount of light through the range printed on the aperture ring--usually f/32. Quoted: Quoted: So, as far as applying what I've learned to shooting: If you have a cheaper 70-200mm lens that has a max apeture of 5.6 at it's peak, it wouldn't be very effective at shooting action or sports shots because it wouldn't let enough light in to be fast enough to capture an action shot? While a more expensive 70-200 that could do 2.8 throughout the length would be fine because of its ability to shoot at 2.8 at 200mm? I guess it depends on how much light you have, indoor or outdoor, etc.  I think you might be fine with the f/5.6, but I doubt it would ever look like a Sports Illustrated shot with subject very sharp against a nicely blurred background.  I could be wrong.  Check out this site if you want to learn about shooting sports: Link here are a couple of things to consider: the sunny /16 rule:  on a sunny day, shooting e.i.100, correct exposure will be 1/60th of a sec at f/16.  if your max aperture is 5.6, you'll be shooting at 1/500th.  this is fast enough for  people sports, but not enough for motor sports, etc.  to shoot these, you'd need to back off your focal length enough to get to f/4, or move to faster film, which is my preference.   constant aperture is your friend:  you are right--a constant 2.8 is going to be a more effective piece of glass.  we're talking 2 full stops at max focal length, which is the difference between shooting at 1/250th and 1/1000th.  remember, each stop of aperture or shutter speed cuts the amount of light in half. now, as for the "SI look", you have to appreciate what factors play into it.  jvic mantioned one--depth of field.  the simplest way to improve the look of your photography is to limit the DOF--sharp subject with blurry background.   3 factors control depth of field   1-focal length.  the longer the lens, the smaller the depth of field. 2-aperture.  the wider the aperture, the smaller the depth of field. 3-point of focus.  the closer to your subject you are, the smaller the depth of field. so the quick and dirty method is to shoot as long as possible, as wide open as possible, and as close to your subject as possible. now, not to sound too cantankerous, but i've taught photography for too long not to include this little tidbit.  the absence of limitation is the enemy of art!--orson wells.  i made my living with a 50, a 43-86 zoom, and a 135, not because i wanted to, but because it was all i could afford at the beginning.  the result of this was that i had to learn to use each lens properly.  instead of hiding behind gear, i had to learn how to be a better photographer.  so when i finally had enough to afford the luxury glass, i could make the most of it. i say that to say this:  if you're trying to decide whether to buy a cheaper zoom now, or to wait and buy a fancier one later, by all means buy the slow one now, and use it to become better.  as you work around the limitations of a slower lens, you'll develop techniques that you never would have considered if not forced into it.  you'll broaden your means of expression, and you'll become a far better photographer for it. best of luck to you, and post some pics. [edit:  tags]

Very good info. Thanks

Another quick question. What's the deal with macro lenses? Are they designed for shooting things extremely close up? Can any lens shoot things close up and a macro just does it better? Can a macro be used for regular distance shots?

Thanks

Quoted: Another quick question. What's the deal with macro lenses? Are they designed for shooting things extremely close up? Can any lens shoot things close up and a macro just does it better? Can a macro be used for regular distance shots? Thanks

Yes, Macro lenses are made to do close-ups well.  Macro lenses can be used as a "regular" lense too.

Part of this article follows: Link

What you want is a macro lens. Fortunately, it is difficult to buy a bad macro lens. This is kind of odd in a world where 90% of the lenses sold are bad. Here's my theory: Every day at least one man wakes up and says to himself "I have a 1.5 inch long penis; I think I will buy a big SLR like a pro. But I don't want to spend money on frills like lenses so I'll get a Tokina zoom." However, no man ever wakes up and says to himself "I have a 1.5 inch long penis. I think I will buy a macro lens so that I can make a 1:1 photograph of my penis and distribute this photo from my Web server. But I don't want to spend too much on this lens so I'll try to find a cheap Sigma."
In short, anyone in the market for a macro lens is already fairly sophisticated and quality conscious. If you read USENET then you know that the world is full of people asking "is this $150 Tamron 75-300 zoom as good as a $900 Nikon 300 prime?" Can you blame Tamron/Tokina/Sigma for trying to separate people like this from their $150? But there isn't apparently a big enough collection of fools in the market for macro lenses to support a junky macro lens subcategory.

In my humble opinion, the best macro lenses are the latest autofocus mount models made by Nikon (my primary 35mm system is Canon EOS, by the way). Nikon makes 60mm, 105mm and 200mm focal lengths. Each lens will focus continuously from infinity to 1:1. You can shoot the moon and capture the bear claw without stopping to change lenses or screw in filters. How do these lenses work? Do they just have a much longer helical than the 50mm normal lens? Yes and no.

Yes a macro lens helical has much more travel than a normal lens helical. You can watch the front element move an inch or two. However, these helicals aren't just pushing a stack of glass back and forth like the 50mm's helical. Inside one of the elements is moving ("floating") so that the optical design changes to a more appropriate one for close-up photography. Thus you get sharp images at all focussed distances.

How do you choose a focal length? The same way you do with a non-macro lens. If you can't get very close to your subject at a soccer game, you don't pull out a 50mm lens; you get a 300. If you can't get close to an insect without it getting scared and flying away, then you want the 200mm lens and not the 50. If you want to compress features in a woman's face, you don't get a 28mm lens; you get a 105mm lens. It is the same with macro work; longer lenses give you a flatter perspective.

What about other companies? Canon makes 50, 100, and 180mm macro lenses. All three incorporate floating elements. The 50 is cheap but it only goes to 1:2 without a "life size converter" (sort of like a telextender) that you stick between the lens and the camera. The 50 is also annoying because it has the ancient non-USM Canon motor. So it can't do simultaneous AF and MF like the ring-USM lenses. The 100 goes to 1:1 but also has the old-style motor. The 180/3.5 is a new design with three low dispersion elements, a tripod mount, and USM for full-time manual focus. It is also compatible with the Canon telextenders. At right, you can see about as close as one can get with the Canon 50 (from my Christina page; part of the reason that photo.net is banned by most of the Net censorship services).

Tamron makes a newish 90/2.8 macro lens that goes to 1:1. It is probably pretty good.

If you like image quality, you're better off getting individual lenses
instead of a zoom.
Most zoom lenses really aren't that good.
Good ones are expensive.
A 28mm, 50mm, 75 or 80mm, and maybe a good 105mm for portraits
is good for a simple set.
Telephotos are good when you want to compress the image and
subject, or you simply are too far away.

Remember, its the photographer, not the camera that takes that
one in a million shot.

Practice, practice, practice.
Always carry your camera everywhere you go.
Use it.

Don't forget that many Digital SLRs have a mutiplier of 1.5X or 1.6X that results in a 50mm lense acting more like a 75mm size-wise.  It's much harder to get wide, but easier to get long.