IS lens vs faster lens. which?

I'm trying to decide between the Sigma 17-70 f2.8-4.5 and the Canon 17-85 f4-5.6 IS. My greatest use will be indoors, no-flash type shots and also low-light forest pics.

I think the 2.8 will be very useful, but don't know if IS will more than make up for the f4 at 17mm. I guess at the longer range the IS is going to work the best. But I'm not sure I'm really understanding this. Does the IS balance out the slower f stop?

Anyone mind helping me figure this out? I'm using the 30D, FYI.

--

Creativity is allowing yourself to make mistakes. Art is knowing which ones to keep.

• Dilbert

Fast Glass always beats IS.

--
'I have been a witness, and these pictures are
my testimony. The events I have recorded should
not be forgotten and must not be repeated.'
-James Nachtwey-
http://www.jamesnachtwey.com/

will be the new 17-55 f2.8 IS. but if it's bw the 1770DC and 1785IS, i'd say for YOUR situation the canon. the sigma is only at f2.8 for a few mm, and the canon's IS will come in very handy for low light forest pics with no flash.

Jada said:

I'm trying to decide between the Sigma 17-70 f2.8-4.5 and the Canon
17-85 f4-5.6 IS. My greatest use will be indoors, no-flash type
shots and also low-light forest pics.

I think the 2.8 will be very useful, but don't know if IS will more
than make up for the f4 at 17mm. I guess at the longer range the IS
is going to work the best. But I'm not sure I'm really
understanding this. Does the IS balance out the slower f stop?

Anyone mind helping me figure this out? I'm using the 30D, FYI.

--
Creativity is allowing yourself to make mistakes. Art is knowing
which ones to keep.

• Dilbert

Click to expand...

--
http://www.pbase.com/fstopjojo/lenstests

A HUGE overgeneralization.

Stovall said:

Fast Glass always beats IS.

--
'I have been a witness, and these pictures are
my testimony. The events I have recorded should
not be forgotten and must not be repeated.'
-James Nachtwey-
http://www.jamesnachtwey.com/

Click to expand...

Jada,

Unless you know you will have needs to narrow the DOF or stop motion in available light, a stabilized zoom for your handheld shooting is one of, if not, THE biggest advantages you can give yourself. Even if you have situations which demand a wide aperture, a stabilized lens is worth owning in its own right. It's the specific reason why I own both the 24-70 L and 24-105 L IS; and the 24-105 sees 5:1 the use of the 24-70.

Times when I use the 24-70 are for indoor available light work, when I can't always guarantee that the subjects will be stationary, or if I need to blow out a background, as would be the case with say weddings. Otherwise, the benefit that IS provides in terms of clarity with each and every shot is so substantial that I simply would not forego it in favor of a wider aperture, without a very specific reason.

Additionally, IS gives you the chance to do some great night-time walkaround shooting that would be either a world harder to get without it, or you'd have to bump the ISO so high, you'd create a poor trade-off in terms of noise and range.

I own primes for tactical "high-performance" work, and one or two zooms that fill specific needs also. However, for the vast majority of the time, my stabilized zooms give me the best results hands down. They're indispensible.

E.

Jada said:

I'm trying to decide between the Sigma 17-70 f2.8-4.5 and the Canon
17-85 f4-5.6 IS. My greatest use will be indoors, no-flash type
shots and also low-light forest pics.

I think the 2.8 will be very useful, but don't know if IS will more
than make up for the f4 at 17mm. I guess at the longer range the IS
is going to work the best. But I'm not sure I'm really
understanding this. Does the IS balance out the slower f stop?

Anyone mind helping me figure this out? I'm using the 30D, FYI.

--
Creativity is allowing yourself to make mistakes. Art is knowing
which ones to keep.

• Dilbert

Click to expand...

I would go for the IS. It doesn't sound like you are shooting much fast action. So the IS would give you a much greater handholding/sharpness advantage than the faster lens. Furthermore, the faster lens loses any advantage it might have had if you stop down the lens, whereas IS still continues to be an advantage when you stop down the lens. Sometimes you want to be able to handhold a shot at f/8 and still get a sharp shot. With the IS lens, you can do that. With the faster lens stopped down to f/8, it's no better than a regular slow lens.

If you want the best of both worlds, consider the Canon 17-55/2.8 IS.

Jada said:

I'm trying to decide between the Sigma 17-70 f2.8-4.5 and the Canon
17-85 f4-5.6 IS. My greatest use will be indoors, no-flash type
shots and also low-light forest pics.

I think the 2.8 will be very useful, but don't know if IS will more
than make up for the f4 at 17mm. I guess at the longer range the IS
is going to work the best. But I'm not sure I'm really
understanding this. Does the IS balance out the slower f stop?

Anyone mind helping me figure this out? I'm using the 30D, FYI.

--
Creativity is allowing yourself to make mistakes. Art is knowing
which ones to keep.

• Dilbert

Click to expand...

Great question.
I find the IS is a lifesaver for longer lens.
Therefore I would get:
85mm f1.8 for low low light
24-70L f2.8 for great shots
Unipod for situations that need it.
Good luck !!

then IS can easily make a lens "brighter." This can be particularly useful for getting greater DoF where you want larger f numbers. I have a 24-70 f/2.8 L and a 24-105 f/4 L IS and when I'm at f/11 to get DoF, the IS lens is three stops brighter. Even at lower f numbers, the IS lens is two stops better.
--
Leon
http://homepage.mac.com/leonwittwer/landscapes.htm

..whereas I share your enthusiasm for fast glass there are a few situations where IS will get you a shot that is not possible with fast glass. Low light, no tripod or flash allowed and wider DOF required...so 'always' is innacurate IMHO

20D, 28-135is iso 400 f5.6 hand held at 1/8th second no flash! My excellent 24-70L would be dead in the water here.



and a crop



with IS off



However under many circumstances the faster lens will indeed trump a slower IS. Though I do not think of the sigma as fast becasue it isn't consistent f2.8 through its range and indeed for night time indoors you need fast primes to be reasonably sure of getting anything that moves.

--
Andy

http://www.pbase.com/wislon

...you'd still be left short if you needed deeper depth of field unless you use as IS lens or a tripod.
--
Andy

http://www.pbase.com/wislon

If there's no motion, just use a tripod....

--
'I have been a witness, and these pictures are
my testimony. The events I have recorded should
not be forgotten and must not be repeated.'
-James Nachtwey-
http://www.jamesnachtwey.com/

IS will make sharp pictures in less-than perfect lighting conditions, but fast glass will produce nice silky bokeh... something IS will never be able to do.

I think IS is not that useful for focal lengths less than 300mm... but YMMV.

-Rich

--
'A wealth of laws creates a poverty of common sense'

Colorado=Home said:

I think IS is not that useful for focal lengths less than 300mm...
but YMMV.

Click to expand...

I have to completely disagree with you there. IS will be useful at any shutter speed that is the same or slower than the inverse of the focal length (1/focal length). For example, if you are using a 50mm (effective) focal length and a shutter speed of 1/50s or slower, you're going to see a benefit with IS. On a 1.6x body, that means you are at physical focal length of 31mm. That's way shorter than 300mm!

The "1/focal length" rule is a general rule of thumb that tells you when your shutter speed puts you into the "danger zone" for handholding at a particular focal length. Just take the (effective) focal length you are at and take the inverse of it. For example, if you are using a 100mm lens on a 1.6x body, which gives you a 160mm effective focal length, apply that to the "1/focal length" rule and you get 1/160. That means that 1/160s is the slowest shutter speed that you should be able to handhold that particular lens without camera/hand shake adversely effecting the sharpness of the image.

What IS allows you to do is break that "1/focal length" handholding rule by effectively being able to handhold at shutter speeds that are much, much slower than the "1/focal length" rule. And it's so easy to see. Just take one shot with IS on, and the next shot with IS off, at a shutter speed at a focal length and shutter speed that you thought IS would not be "useful" and more often than not you will see that the IS shot will be sharper. For example, on my 100-400L IS, I can confidently handhold the lens at any focal length between 100-400mm at a shutter speed of 1/60s and still get a very sharp shot. If I turn off IS, I get a noticeable drop in sharpness because the 1/60s shutter speed is slower than the "1/focal length" rule. In other words, that shutter speed puts me into the danger zone for handholding. And on my 28-135 IS, I've gotten very good results at 28mm even when using a shutter speed of 1/20s. And IS can be of benefit at higher shutter speeds, too, depending on how steady (or unsteady) your hands are.

The usefulness of IS depends on a combination of focal length and shutter speed. To make a blanket statement that " IS is not that useful for focal lengths less than 300mm..." without any regard to shutter speed is very short-sighted. Try handholding an 85mm focal length at 1/45s or 1/60s using IS versus not using IS and it's quite easy to see that IS is a benefit at focal lengths much, much shorter than 300mm.

I agree. There are many more situations IS will help you but speed will not. When you want to have decent DOF in low light, e.i. landscapes, street scenes at dusk or even after dark. Speed is useless. I take 3 stop IS over one stop speed any day of the week.

This one was shot at 1/3 sec hand held with 24-105.

Andy Wilson said:

..whereas I share your enthusiasm for fast glass there are a few
situations where IS will get you a shot that is not possible with
fast glass. Low light, no tripod or flash allowed and wider DOF
required...so 'always' is innacurate IMHO

20D, 28-135is iso 400 f5.6 hand held at 1/8th second no flash! My
excellent 24-70L would be dead in the water here.



and a crop



with IS off



However under many circumstances the faster lens will indeed trump
a slower IS. Though I do not think of the sigma as fast becasue it
isn't consistent f2.8 through its range and indeed for night time
indoors you need fast primes to be reasonably sure of getting
anything that moves.

--
Andy

http://www.pbase.com/wislon

Click to expand...

I think this comment is way off. Please see my post in this tread a few minutes ago. FL was 24mm.

Colorado=Home said:

I think IS is not that useful for focal lengths less than 300mm...
but YMMV.

-Rich

--
'A wealth of laws creates a poverty of common sense'

Click to expand...

You belive one stop faster lens beats 3 stop IS? I can't see the logic there if it's a general statement.

Stovall said:

Fast Glass always beats IS.

--
'I have been a witness, and these pictures are
my testimony. The events I have recorded should
not be forgotten and must not be repeated.'
-James Nachtwey-
http://www.jamesnachtwey.com/

Click to expand...

Stovall said:

If there's no motion, just use a tripod....

Click to expand...

Tripods tend to be a lot heavier, more cumbersome, and slower to set up than simply having IS. What IS allows you is freedom and mobility that a tripod simply doesn't give you. When traveling or hiking, I greatly prefer to use an IS lens rather than having to lug around a tripod. You tend to miss a lot of shots while scrambling to set up a tripod, rather than just being able to point, compose, shoot, and move on thanks to the effectiveness of IS. You can also shoot a lot more variations of the same shot (different compositions, angles, positions) with IS than you can with a tripod. A tripod tends to "lock" you down to a particular position, and changing that position takes much more effort. Other times, it's simply impractical to use a tripod.

Read this: http://forums.dpreview.com/forums/read.asp?forum=1029&message=17806679

Remember also that you have to take in account,when choosing between two primes that have different focal lenghts that longer focal lenght means that its "allowed handholdable time" is shorter. So, a 50 needs 1/80s (on a 1.6 crop camera) approx. while a 30 needs 1/50s. There are 2/3 of stop between these 2 exposure times. If they have the same max largest aperture, the 30 will allow you to shot a 2/3 of stop darker scene.

Jada said:

I'm trying to decide between the Sigma 17-70 f2.8-4.5 and the Canon
17-85 f4-5.6 IS. My greatest use will be indoors, no-flash type
shots and also low-light forest pics.

I think the 2.8 will be very useful, but don't know if IS will more
than make up for the f4 at 17mm. I guess at the longer range the IS
is going to work the best. But I'm not sure I'm really
understanding this. Does the IS balance out the slower f stop?

Click to expand...

Personally, I would hold out for the EF-S 17-55 f/2.8 IS.

--
Whoever said 'a picture is worth a thousand words' was a cheapskate.

http://www.pbase.com/dot_borg

I'm not arguing the utility of IS, but just it's application.

I see no need, for my shooting style, to have IS on any of my lenses that are 300 or less in focal length. I do have it on my 70-200, and honestly would not want to see it go away even within that focal range... but for wide to normal length shots, I don't see a need. I have IS on my 300 and my 500, and on these lenses, I view IS as a "must-have" option... it's saved my butt more than once.

But like I said in my post - YMMV... and we don't see eye to eye on the utility of this technology for shorter focal lengths. That's cool, and I can respect where you're coming from. It's really just personal opinion and shooting style.

-Rich

--
'A wealth of laws creates a poverty of common sense'