do image stabilisers decrease image quality?
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This is all very amusing, but it doesn't seem as though anyone is answering the OP's question. As I understand it, he/she is asking if the addition of optical image stabilization negatively impacts the sharpness of a lens.
I'm like the least technical person on this whole forum, so I'm certainly not qualified to answer this. But it does seem like a good question. I might expand on it a bit.
First, the idea that adding lens elements would degrade an image seems irrelevant because, as I understand it, stabilized lenses don't have any more or less elements. (That doesn't mean there aren't a different number of lens elements in a stabilized lens vs. an stabilized lens, just that the two are not related to one another.)
I think a more relevant question might be whether or not the construction of a stabilized lens sacrifices sharpness under certain conditions. From what I have read, the difference between stabilized and non-stabilized lenses is in how a group of lens elements are mounted within the lens – not the actual design of the lens elements. In a stabilized lens, a group of elements are mounted in a housing that uses gyroscopes to keep the elements stable when the housing shifts or moves. So, I guess the question really would be: since the lens elements effectively "float" within the IS housing, is there a reason why they might not be as sharp as elements that are solidly mounted within a lens tube?
One reason this seems like a logical question is that Canon recommends turning off stabilization when a lens is mounted on a tripod. If you get a sharper image without stabilization on, when the camera is firmly mounted, it does at least raise the possibility that a non-stabilized lens would be sharper than a stabilized lens.
Okay, all you tech geeks, have at it.
I'm like the least technical person on this whole forum, so I'm certainly not qualified to answer this. But it does seem like a good question. I might expand on it a bit.
First, the idea that adding lens elements would degrade an image seems irrelevant because, as I understand it, stabilized lenses don't have any more or less elements. (That doesn't mean there aren't a different number of lens elements in a stabilized lens vs. an stabilized lens, just that the two are not related to one another.)
I think a more relevant question might be whether or not the construction of a stabilized lens sacrifices sharpness under certain conditions. From what I have read, the difference between stabilized and non-stabilized lenses is in how a group of lens elements are mounted within the lens – not the actual design of the lens elements. In a stabilized lens, a group of elements are mounted in a housing that uses gyroscopes to keep the elements stable when the housing shifts or moves. So, I guess the question really would be: since the lens elements effectively "float" within the IS housing, is there a reason why they might not be as sharp as elements that are solidly mounted within a lens tube?
One reason this seems like a logical question is that Canon recommends turning off stabilization when a lens is mounted on a tripod. If you get a sharper image without stabilization on, when the camera is firmly mounted, it does at least raise the possibility that a non-stabilized lens would be sharper than a stabilized lens.
Okay, all you tech geeks, have at it.
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neuroanatomist said:
That's a variance. Like a half-truth, just sayin'.
neuroanatomist said:
Agreed.
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you actually dont need a lens to take a picture. you do however need an aperture to direct light towards a medium that will record the picture. unless you consider photograms using non silver chemistry and then you dont even need an aperture.
i dont know the engineering or physics involved with IS as it pertains to image quality but i do know that a person who doesn't understand how IS is intended to be used can quickly find their image quality degrade from user error. i work with a guy who repeatedly insists on shooting in daylight with IS turned on with shutterspeeds slower than 1/60th of a sec on a 70-200mm and is shocked that he continues to get camera shake in his images....
*edit*
a gyro will create some level of vibration so at a certain point image stabilization becomes moot due to increasingly slow shutterspeeds being much more sensitive to the vibration. i imagine that is why canon recommends turning IS off when on a tripod because the assumption is that your shutterspeeds will decrease with the use of a tripod.
i dont know the engineering or physics involved with IS as it pertains to image quality but i do know that a person who doesn't understand how IS is intended to be used can quickly find their image quality degrade from user error. i work with a guy who repeatedly insists on shooting in daylight with IS turned on with shutterspeeds slower than 1/60th of a sec on a 70-200mm and is shocked that he continues to get camera shake in his images....
*edit*
a gyro will create some level of vibration so at a certain point image stabilization becomes moot due to increasingly slow shutterspeeds being much more sensitive to the vibration. i imagine that is why canon recommends turning IS off when on a tripod because the assumption is that your shutterspeeds will decrease with the use of a tripod.
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The inclusion of an image stabilization system in a lens DOES often lead to reduced image quality, BUT not all lenses that are poor quality have image stabilization and not all lenses that are of good quality lack image stabilization. For proof look at any lens that comes in IS and NON-IS format released in the SAME technological cycle. Tamron, Canon, Nikon, Sigma etc al have had lenses that meet that criteria and the IS version has worse IQ.
Adding image stabilization is like making a rocket that can land on the moon then deciding to make it go to mars afterwards, it's going to be harder than just making a rocket that goes to the moon, but that doesn't mean you can't achieve IQ perfection with IS, you certainly can, it's just harder.
Adding image stabilization is like making a rocket that can land on the moon then deciding to make it go to mars afterwards, it's going to be harder than just making a rocket that goes to the moon, but that doesn't mean you can't achieve IQ perfection with IS, you certainly can, it's just harder.
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PackLight
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unfocused said:
I think you described it right from all I have read and seen. The IS doesn't add another element so if it is turned off it wouldn't have any affect.
If you have the IS on while on the tripod and it kicks on it could cause motion blur, and then would affect IQ. That is one reason to turn it off. The other is battery life.
The OP's question might have been better said can they design a sharper lens by leaving the IS out. Chuck Westfall mentioned this at the release of the 24-70mm II, if memory serves. The comment was that the IS was left out to get the very best image quality out of the 24-70mm II. What this really meant who knows, but it could have meant just as easily that other versions that could have been in the target price range wouldn't have had the same quality lens grouping. It could be that IS could have been put in the new 24-70mm II for a substantial price above the $2300 the lens is going for now. Imagine how a $3000 24-70mm f/2.8 II version would have been received by the public. I don't think Westfall's comments shed any light on the question the OP posed.
I am of the opinion that IS has no affect, other than if it is miss used or malfunctions.
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PackLight
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Sanj, how could it do anything to IQ? It is a mechanical device outside of the row of elements in the lens, it is not optical.
The only way it would affect optics is if it doesn't work properly.
But really this thread is about a non issue. There is no IS vs non IS lens that Canon makes that would be equal, those that are close the IS version is superior to the Non IS version.
The only way it would affect optics is if it doesn't work properly.
But really this thread is about a non issue. There is no IS vs non IS lens that Canon makes that would be equal, those that are close the IS version is superior to the Non IS version.
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Is there ever an advantage in turning IS off? (Ignoring tripod mounted cameras and assuming a sufficently fast shutter speed for a sharp photo.) I often see it stated that it results in sharper images, but my experiences have been inconclusive. Any thoughts?
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PackLight said:
Yes, something is lost, and it is light.
But ... does IQ get worse with each additional element, as he said? If so, why not a 1 or a 2 element lens? IQ should be much better than those 22 element lenses - less CA, sharper, less distortion, etc - Really ?? Where are those one or two element lenses with superior IQ, or for that matter, 5 element lenses?
Its a nice theory, but the best lenses with the best IQ have many elements, and they do lose light, but not all that much. The 9 element 85mm f/1.8 has a Tstop of 2, so it loses 0.2 stops in the glass. The 20 element 70-200mm f/4L IS has a Tstop of 4.6, so it loses 0.6 stops. 20 elements, and it has suburb IQ and sharpness!
So, how many elements until you lose a stop? Maybe 30 some elements? Your worry that light won't make it thru a lens due to the number of elements seems a bit far fetched.
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My feeling is that IS would affect IQ as the lens or lenses in the IS unit are moved off center, to negate movement of the photographer. This process of moving the lenses off axis in the optical path would have been "allowed" in the design, but it'll be a case of "....the lesser of 2 evils".
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PackLight
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Mt Spokane Photography said:
It is more than just light lost, it is the quality of the light itself, how the light breaks down going through the lens.
It does get worse with each element, because each progressive element corrects one problem and adds another, or not depending. If the lens has 20 elements the last element corrects flaws made through one or more of the previous 19. It will never be perfect and each element takes away, even if it is slightly. There is more lost than just light and loosing a stop, that is why we look for other flaws in our IQ other than just sharpness or quantity of light. No doubt the L lenses deliver great IQ with multiple elements, but it doesn't change that fact that a bit of quality is lost with each element.
A single lens that produces an image with little or no flaw is possible. The human eye has only one lens. Glass and Crystal lenses abilities are flawed in comparison.
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"Its a nice theory, but the best lenses with the best IQ have many elements, and they do lose light, but not all that much. The 9 element 85mm f/1.8 has a Tstop of 2, so it loses 0.2 stops in the glass. The 20 element 70-200mm f/4L IS has a Tstop of 4.6, so it loses 0.6 stops. 20 elements, and it has suburb IQ and sharpness! "
Not sure that's correct. The first thing is that just because a lens says "1.8" or "4" does not mean that it is 1.8 or 4 in an optical sense. Just like 70mm on the 70-200mm is not actually 70.
Secondly, a 1.8 lens with a T-stop of 2 is a loss of 11%, whereas the f4 lines with a T-stop of 4.6 loses 15%. A loss of a full f-stop represents a 40% difference between f number and T-number, so the first lens loses about 0.27 of an f-stop and the second about 0.37 of an f-stop.
But my nit-picking aside, in principle you are right, extra elements will absorb or reflect more light, reducing the light passing through the lens, just not as much as you suggest. Others have commented on how extra elements can correct distortions and improve IQ.
Not sure that's correct. The first thing is that just because a lens says "1.8" or "4" does not mean that it is 1.8 or 4 in an optical sense. Just like 70mm on the 70-200mm is not actually 70.
Secondly, a 1.8 lens with a T-stop of 2 is a loss of 11%, whereas the f4 lines with a T-stop of 4.6 loses 15%. A loss of a full f-stop represents a 40% difference between f number and T-number, so the first lens loses about 0.27 of an f-stop and the second about 0.37 of an f-stop.
But my nit-picking aside, in principle you are right, extra elements will absorb or reflect more light, reducing the light passing through the lens, just not as much as you suggest. Others have commented on how extra elements can correct distortions and improve IQ.
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PackLight said:
I don't know but am trying my best to understand!
I bought the X100 and asked the Fuji 'guys' about IS and this is what they said:
Hello Greg and Billy.
Great video, great camera! Mine will be with me end of this month...!!
Could you please educate me on one point:
Why is incorporating Stabilization into the camera a bad idea: Does it:
a) Increase costs?
b) Increase size?
c) Reduce quality?
Asking because I am sure ISO 400 results in better quality than ISO 3200 (which 4 stops stabilization would provide.)
I understand that u guys strongly believe that this camera does not require IS but my question is: HOW CAN IT HURT?
Sanjay Gupta 1 year ago
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A) Yes, B) Yes, C) Yes as the ability for customization of the lens to the sensor would not be possible (well at least cost effective). I believe in I.S. however not so much with a 35mm equivalent lens. Especially the quality of ISO settings up to 3200 and a fast lens should allow for decent shutterspeeds for most situation. Others, use a tripod, or enable the flash.
Fuji Guys - X100 Frequently Asked Questions
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PackLight
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Frodo said:
I am not sure how much I suggested, I didn't put a quantity to it. Maybe the difference is small and slight but it is still there.
Extra elements do not improve the quality of the original light. They correct the flaws of the other lenses. The additional elements improve the IQ and flaws in the light that was created by other lenses. Just because a lens has 20 elements doesn't make it a superior lens by quantity only, it is a lens that took 20 elements to get the IQ back to a usable form.
The elements do more than absorb and reflect, it also breaks down the light. It alters the colors that you will get. When comparing lenses it is common to talk about chromatic aberrations, sharpness, color, distortion and flare. All these items have an impact on IQ, and I haven't seen a lens made yet that took 100% of these lens created aberrations out.
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I think that there is no simple answer to your question. Trying to break it into different paths:
[list type=decimal]
[*]IS itself: If well programmed and eqiupped with good actor hardware it will not blurr the image by wrong corrective movements
[*]IS uses additional lens elements in most stabilized lenses and needs sometimes additional lens groups in the rest of the optical path. The number of lens elements is increased. Optical calculation of such systems is very complex because the moveable lns element has to correct movements correctly and at the same time it has to keep IQ at a high level.
This splits into to paths:
[list type=decimal]
[*]If the calculation of the lens is done very carefully, IQ will remain very good.
[*]If the calculation is done less carefully or the price limit cuts into optimization quality, IQ will decrease.
[/list]
[*]If you have a simple lens design movement of one lens element will give usable results, but I think extreme values of corrective movements will cut into IQ.
[*]If IS gives you 4 exposure steps, you have 16 times lower movements due to camera shake - if the IS element reduces resolution by a factor 1.2 you will gain roughly 12 times more sharpness in comparison to an unstabilized lens.
[*]Additional lens elements reduce the contrast of a lens - if you use the same measures to suppress reflections and light scattering on lenses and structural elements. But if you go from 13 lens groups w/o IS to 15 lens groups w/ IS this is a small difference (70-200 4.0 non IS vs. IS). If you go from 6 to 12 groups it might be another thing (5.6/400 vs. 2.8/400 ii).
On the other hand additional lens elements improve IQ by correcting different aberrations if the calculation is done properly and if there is no strong price limit.
[/list]
IMO there are applications of IS lenses: If a tripod isn't allowed/appropriate and low aperatures are essentially needed to gain enough DOF/the light is limited.
The new 4.0 24-70 IS lens might address these application fields. I think it is a good addition of the EF lens family ... if the quality is phenomenal and the street price will come into the region of the 24-105.
[list type=decimal]
[*]IS itself: If well programmed and eqiupped with good actor hardware it will not blurr the image by wrong corrective movements
[*]IS uses additional lens elements in most stabilized lenses and needs sometimes additional lens groups in the rest of the optical path. The number of lens elements is increased. Optical calculation of such systems is very complex because the moveable lns element has to correct movements correctly and at the same time it has to keep IQ at a high level.
This splits into to paths:
[list type=decimal]
[*]If the calculation of the lens is done very carefully, IQ will remain very good.
[*]If the calculation is done less carefully or the price limit cuts into optimization quality, IQ will decrease.
[/list]
[*]If you have a simple lens design movement of one lens element will give usable results, but I think extreme values of corrective movements will cut into IQ.
[*]If IS gives you 4 exposure steps, you have 16 times lower movements due to camera shake - if the IS element reduces resolution by a factor 1.2 you will gain roughly 12 times more sharpness in comparison to an unstabilized lens.
[*]Additional lens elements reduce the contrast of a lens - if you use the same measures to suppress reflections and light scattering on lenses and structural elements. But if you go from 13 lens groups w/o IS to 15 lens groups w/ IS this is a small difference (70-200 4.0 non IS vs. IS). If you go from 6 to 12 groups it might be another thing (5.6/400 vs. 2.8/400 ii).
On the other hand additional lens elements improve IQ by correcting different aberrations if the calculation is done properly and if there is no strong price limit.
[/list]
IMO there are applications of IS lenses: If a tripod isn't allowed/appropriate and low aperatures are essentially needed to gain enough DOF/the light is limited.
The new 4.0 24-70 IS lens might address these application fields. I think it is a good addition of the EF lens family ... if the quality is phenomenal and the street price will come into the region of the 24-105.
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100mm 2.8L IS is one of the sharpest lenses out there i think 
Probably Is can degrade IQ by helping u in situations where without IS u would get motion blur but IS reduces it like 98% for example but not 100%. So thats when it perhaps could cause "worse IQ"
Probably Is can degrade IQ by helping u in situations where without IS u would get motion blur but IS reduces it like 98% for example but not 100%. So thats when it perhaps could cause "worse IQ"
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