Canon EF-S 17-55 F2.8 IS USM
- Thread starter donnyyeo
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When an element is not aligned properly, you get photos that are soft on one side, either left/right or top/bottom, depending on how the element is misaligned.
chewraisins
New Member
I think what it means is that you could shoot hand-held at shutter speed that is 3 f-stop longer.. but if subject is in motion, you'll get more motion blur compared to F1.4 lens shooting at faster shutter speed.
All the sifu here please correct me if i'm wrong..
I think what it means is that you could shoot hand-held at shutter speed that is 3 f-stop longer.. but if subject is in motion, you'll get more motion blur compared to F1.4 lens shooting at faster shutter speed.
All the sifu here please correct me if i'm wrong..
Yup right idea. It means you can shoot at up to three stops slower than the supposed minimum shutter speed based on 1/focal length.
For instance, at 55mm, your slowest should be 1/60s (closest to 1/55), but with IS you get to go three stops slower, which will bring you to 1/8s.
Just in addition, an f/stop is a standardised way of measuring exposure (another unit of measurement is foot candles (fc)), and may not necessarily always refer to aperture value, but don't think too much about this, or you'll get confused.
so just to confirm. it's correct to say that it's like a F1.4 lens?
No. Please re-read slowly. It's still an f/2.8 lens, and you still have to shoot at the correct shutter speed to get accurate exposure, but with IS, you can shoot up to three stops slower than the minimum shutter speed.
patience please as i'm bit confused..
from your example
#1. at 55mm, 1/60s, F2.8, NO IS
#2. at 55mm, 1/8s, F2.8 With IS
Now, If I have a faster lens, how can I duplicate the IS advantage at #2?
Thanks.
Stop thinking faster lens.
IS minimises handshake; it doesn't help you stop motion unlike a faster lens.
With IS, you can shoot #2 with minimised handshake. Without IS, chances are you'd have to shoot at #1 to minimise handshake. Get the idea?
Thanks for your patience bro...
let say we forget about #1 one first. i have this lens, metered the scene at 55mm and get 1/8s, F2.8 With IS enabled. this is acceptable to shoot right? because of IS. Now I'm still in the same scene but I changed to no IS lens, same focal-length. Meter will read 1/8s @ F2.8 right? which will cause blurry image. So I need to open up the aperture or increase ISO (which I don't want) to reach 1/60s? What aperture value should it be?
The aperture value would be f/1.4, assuming all lighting remains the same. You see, because you were thinking of it this way, that's why you were confused.
raymond350
New Member
For EF-S bodies, i think it should be 1/focal length x 1.6 = approx 1/80 s.
Nope. You are confused. 55mm will always still be 55mm. It's not lengthened in any way by any body. It's still 1/55.
miniUltraman
Senior Member
Hi bro, let me try to explain too :bsmilie: let's not think about f1.4. Like Calebk said it is still f2.8.
Here is my example.
Base on a certain lighting condition, you meter at a particular subject with Aperture priority, the camera reads f2.8, shutter speed 1/8 to give you the right exposure.
Supposingly, base on your own experience, you know you can handhold steadily at @1/50 or faster. Anything below this speed, you encounter handshake.
OK. Next question - What is 3 stops after 1/8? i.e. 1/8 1/15 1/30 1/60
So with 3-stop IS, it means at f2.8, it is as though you are handholding it at 1/60 (even though the meter tells you 1/8). Thus, you can get a steady good picture at 1/8 (since 1/60 is faster than your steady handholding speed of 1/50)
Nevertheless, the lens does not really function at 1/60, thus, no action freezing.. the shutter speed is still essentially 1/8.
Did I help clarify or confuse you further?:dunno:
Nope, you are confused.
He is talking about the handholding rule being affected by the crop factor, which was debated sometime ago in some other thread.
Just look at an object that is at a reasonable distance from your eyes; look at it again through a straw.
Your eyes don't gain any magnification just by looking at the object through the straw, but it may not easy maintain a steady view since slight movements of the head is amplified.
miniUltraman
Senior Member
My explanation so bad arh :bsmilie: The rule is if you cannot convince.. you confuse.. haha!!!
Believe what you want; I haven't multiplied it by anything since I've went digital, and it works perfectly fine.
I believe your illustration refers to a smaller image circle, not a smaller sensor. The eye (sensor) is still the same size, but your image circle (initially the whole retina, but now the straw's internal circumference) is reduced.
flyer
New Member
Basically, what miniultraman is saying is that even though you can handhold at 1/8 as though it is as steady at 1/60, it still cannot freeze action as though the shot was taken at 1/60. If you try to take a subject that is moving, it will still have motion blur in your shot because the shot was taken at 1/8 and that's not enough to freeze the subject and not because of handshake at 1/8. Any foreground/background that is not moving will be clear though.
oh well, OT-ing: - Indeed, I am free to believe I want.
The Canon guys account for the crop factor for the 1/focal length handholding guideline when publishing the Lens Workbook.
I believe it to be so based on the fact that when viewed at 1:1, camera shake that wasn't visible becomes obvious in some photos.
You are free to believe it isn't, your perogative, anyway you've hinted that you've been shooting for a while.
In any case, I'll attempt to shoot @ 1/5s on my Sony Ericsson mobile with an actual focal length of 4.8mm and at around 1/30s on the A630 at maximum telephoto. Sure beats anonymous arguing on a forum.
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