December 22, 2014, 10:05:03 AM

Author Topic: Why do fast primes not have IS?  (Read 5021 times)

mb66energy

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Re: Why do fast primes not have IS?
« Reply #15 on: June 24, 2014, 03:11:26 PM »

I will try to make an approach, as far as I can handle your question:
IS (Canon) is a moving optical element inside the lens.
http://en.wikipedia.org/wiki/Image_stabilization
To work properly it has to move fast and accurate. To be fast it has to be of low weight.

Fast apertures need a larger image circle over the whole optics compared to narrow apertures.
Therefore the optical elements of the IS should be larger as well. This leads to higher weight which causes loss of speed and higher energy consumption and also to higher prices because of the more expensive optics.
So with IS Canon always compromises between functionality of the IS and useful max. aperture.

This is my conclusion. Maybe someone else can do better.

Superteles with IS have large elements.

Weight and energy consumption should therefore be even greater, per your explanation.

Does the larger housing of the superteles provide more space for the mechanism that moves the elements?

Comments?

Superteles have large front elements but the IS group is mostly a thin lens element of much smaller diameter nearer to the bajonet than to the front element.

In standard lenses and wide angles you need smaller radii for the lens surfaces so the lenses become thicker and have higher mass - this implies higher forces to reposition them fast enough to counteract camera shake etc.

But your argument - in a tele you have more space - might be an additional reason.

A third one: A 2.8 300mm lens typically costs several thousands of dollars - 500 dollar more for a fast IS isn't prohibitive, it's a 10% increase of the cost or price. For a fictional EF 1.8 50 IS it means a 500% increase of cost or price!
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Re: Why do fast primes not have IS?
« Reply #15 on: June 24, 2014, 03:11:26 PM »

CANONisOK

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Re: Why do fast primes not have IS?
« Reply #16 on: June 24, 2014, 03:16:29 PM »
I'm sure I'll get throttled for this comment but here it goes: typically, I don't stop down my f/1.2 lenses a whole lot. Sort of negates the point of having them. Therefore I tend to use pretty decently fast shutter speeds relative to the focal length. Others may use theirs differently of course.

+1.......I don't see the point buying f1.2 lens and shoot at f4. On Canon lenses, I like to turn down the dial twice - hit sweet spot everytimes ;)
+1. Exactly. If I want something with more DOF, I'll show up with the 24-70ii or the 70-200ii, not a fast prime. There would be more argument for IS in the 24-70ii, as it a slower lens.
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Re: Why do fast primes not have IS?
« Reply #17 on: June 24, 2014, 03:32:51 PM »
I'm wondering why fast primes like a 35/1.4 or a 85/1.2 don't come with IS. The fastest lens to feature IS is the 35mm (and the 200mm) f2. Why is that?  :o People would love a 50mm f1.2 IS  ::) Is there some sort of technical problem? I can't imagine anything else, it would sell well, would set them apart, isn't too expensive... Can someone help me?  :)

Those lenses were designed several years ago for full frame cameras.  IS was not needed for shorter focal lengths, and did not really start appearing in "L" in lenses until about 1999.  It appeared in a consumer zoom in 1995.
 
Adding IS increased the cost, and like any new feature, it was expensive.  The main benefit of IS was in the longer focal lengths where camera shake and vibration was difficult to eliminate blurring. 
With the advent of APS-C Rebel bodies in about 2002,  consumers were able to afford Digital DSLR's, and because of the 1.6 crop factor, a 200mm lens was more prone to blurring from shake, and because inexperienced users could just snap off a shot without carefully setting up, the feature became popular and started appearing in APS-C lenses of much wider focal lengths.  The feature sold very well, so lenses have been adding the feature where possible.  The new 24-70 f/2.8L does not have it.  There were prototypes with IS, but apparently, it was not considered good enough or necessary for that lens.
Now, with video in DSLR's becoming popular, IS in wide focal lengths and fast primes has finally found a reason to exist.  Handheld video really benefits from IS.  That's why we are seeing new prime lenses with IS.  They are not f/1.4 or faster, presumably because of the expense and difficulty, but they will come, it can be done, its just a matter of price. 

CANONisOK

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Re: Why do fast primes not have IS?
« Reply #18 on: June 24, 2014, 03:37:46 PM »
+1.......I don't see the point buying f1.2 lens and shoot at f4. On Canon lenses, I like to turn down the dial twice - hit sweet spot everytimes ;)

I see it a different way.  I buy a 1.4 lens, not because I want to shoot at 1.4, but because I want sharp images at 2.8 -- stopped down 2 stops.   That way on those shots when I need to shoot at 1.4, I can, but for most of the shots I can easily shoot stopped down. 

It all depends on what type of photography each photographer does.  Some like to shoot wide open, others like to stop down.  I guess that's why they make changable apertures on lenses.   ;D
If you want sharp pictures at 2.8, you need the 24-70ii or the 70-200ii.

http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=397&Camera=453&Sample=0&FLI=0&API=4&LensComp=687&CameraComp=453&SampleComp=0&FLIComp=0&APIComp=0
http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=403&Camera=453&Sample=0&FLI=0&API=5&LensComp=787&CameraComp=0&FLIComp=0&APIComp=0

Just as sharp in center, more corner sharpness, less CA, probably a hair of distortion but that can be fixed in post. And you can change the FL. The right tool for the job.
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sdsr

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Re: Why do fast primes not have IS?
« Reply #19 on: June 24, 2014, 03:49:57 PM »
By the way, there are *some* fast primes with IS - e.g. Sony makes some 1.8 APS-C e-mount primes that have it (35mm & 50mm; maybe others).

Maximilian

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Re: Why do fast primes not have IS?
« Reply #20 on: June 25, 2014, 02:09:58 AM »

I will try to make an approach, as far as I can handle your question:
IS (Canon) is a moving optical element inside the lens.
http://en.wikipedia.org/wiki/Image_stabilization
To work properly it has to move fast and accurate. To be fast it has to be of low weight.

Fast apertures need a larger image circle over the whole optics compared to narrow apertures.
Therefore the optical elements of the IS should be larger as well. This leads to higher weight which causes loss of speed and higher energy consumption and also to higher prices because of the more expensive optics.
So with IS Canon always compromises between functionality of the IS and useful max. aperture.

This is my conclusion. Maybe someone else can do better.

Superteles with IS have large elements.

Weight and energy consumption should therefore be even greater, per your explanation.

Does the larger housing of the superteles provide more space for the mechanism that moves the elements?

Comments?
Hi Larry!
Superteles have larger FRONT elements and other lager non moving optical elements in their design.
The IS is normaly set at a point where the image circle is very small.
Maybe you are right, that the IS element in the big whites is bigger than inside the 70-200 for example.
But maybe this is also one important reason for the much higher price.
« Last Edit: June 25, 2014, 02:42:05 AM by Maximilian »
sometimes you have to close your eyes to see properly.

Maximilian

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Re: Why do fast primes not have IS?
« Reply #21 on: June 25, 2014, 02:18:44 AM »
http://en.wikipedia.org/wiki/Image_stabilization
I also think that there is a degradation that comes with thee things and the companies that are making fast primes are generally going for the best MTF curve they can get.  So putting the IS gizmo in there costs them some performance in that regard.  Zooms are always a compromise so for those it doesn't matter as much (and they are already big and heavy).
Of course you are right!
I forgot to mention it directly but it was included in the wikipedia article.
I think this degradation is an issue you can handle by QC and higher quality and prices for the IS element.
See the 24-70 IS L II or the 70-200 IS L II.  edit: Sorry! Made a mistake!
« Last Edit: June 25, 2014, 03:15:04 AM by Maximilian »
sometimes you have to close your eyes to see properly.

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Re: Why do fast primes not have IS?
« Reply #21 on: June 25, 2014, 02:18:44 AM »

rs

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Re: Why do fast primes not have IS?
« Reply #22 on: June 25, 2014, 03:06:43 AM »
See the 24-70 IS L II or the 70-200 IS L II.
I though we're still on the first version of that f4 lens?  ::)
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Maximilian

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Re: Why do fast primes not have IS?
« Reply #23 on: June 25, 2014, 03:11:58 AM »
See the 24-70 IS L II or the 70-200 IS L II.
I though we're still on the first version of that f4 lens?  ::)
touche! :-[
I was dreaming about the EF 24-70mm 2.8L II USM having IS.
Thank you for leting me correct this.
sometimes you have to close your eyes to see properly.

Grumbaki

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Re: Why do fast primes not have IS?
« Reply #24 on: June 25, 2014, 03:49:29 AM »
By the way, there are *some* fast primes with IS - e.g. Sony makes some 1.8 APS-C e-mount primes that have it (35mm & 50mm; maybe others).

1.8 ASP-C is not really fast glass...

AvTvM

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Re: Why do fast primes not have IS?
« Reply #25 on: June 25, 2014, 04:35:07 AM »
With FF mirrorless cameras taking over some time soon (I hope  ;) ), in-lens IS loses one of it's two advantages over in-body IS: on an EVF, viewfinder image will be stabilized, irrespective of whether IS is implemented in-lens, in-body .. or even in a dual/hybrid way using both. [Second advantage for in-lens IS being the fact that it's specifically tailored to match a specific lens ... and I do not believe this holds much truth any longer against todays in-body IS systems)

So while Canon (and Nikon) had a major advantage with their in-lens IS approach during the (D)SLR era, this is coming to an end.

Personally, I would prefer a Canon FF mirrorless system, of course with new, native, short flange-distance lens mount. Ideally with in-body IS, and lenses without any manual focus gears, only "by-wire" in a really well-implemented fashion. Zoom also "by wire". Either turning rings on lenses or really good, highly ergonomical control points on camera body. Ideally also with non-mechanical aperture ... think of something like a variable, highly transmissive LCD with a perfectly round aperture opening at all openings .. also implemented in body, rather than in evry lens.

To complete my vision of future "solid state" mechanics-free FF-sensored cameras, shutter would be fully electronic.

If the in-body IS could be extended to "6 axis", i.e. adding linear movement in the Z-axis [current 5-axis systems (Oly) allow linear and rotational moves in the X and Y axis and rotational moves around the Z axis] ... then focussing could possibly also take place in the body, without any moving lens elements. With proper lens construction, that is.

This would possibly allow for camera/lens systems with significantly smaller, lighter, simpler, more robust, fully weathersealed, higher IQ [only needs to be adjusted/centered once before leaving factory] lenses ... at significantly lower production cost ... and hopefully prices.  8)

Not sure however, whether I'll live long enough to get it from Canon.  :P


Meanwhile I do expect Canon to come up with in-lens IS in fast primes as well. 50/1.4, 50/1.8, 85/1.8 + 100/2.0 are all very old lens designs and in need of a major overhaul, with the same treatment Canon gave the 24/28/35 IS primes. Not only IS and (corner) sharpness, but also less (lonigtudinal) CAs, please.
« Last Edit: June 25, 2014, 06:14:23 AM by AvTvM »

GMCPhotographics

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Re: Why do fast primes not have IS?
« Reply #26 on: June 25, 2014, 04:51:48 AM »
I have a 400mm f2.8 LIS. It's a fast prime and it's got an image stabiliser.
I have a 24mm f1.4 L, it doesn't need and IS unit because it can be shot hand held at 1/25th second easily and due to it's huge light gathering capabilities, it can shoot at light levels several stops below what an f2.8 lens can achieve. So what could an Is offer a 24mm f1.4? Very little.

AvTvM

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Re: Why do fast primes not have IS?
« Reply #27 on: June 25, 2014, 06:17:17 AM »
I have a 400mm f2.8 LIS. It's a fast prime and it's got an image stabiliser.
I have a 24mm f1.4 L, it doesn't need and IS unit because it can be shot hand held at 1/25th second easily and due to it's huge light gathering capabilities, it can shoot at light levels several stops below what an f2.8 lens can achieve. So what could an Is offer a 24mm f1.4? Very little.

2 stops [2.8 - 2.0 - 1.4]  ... to be precise.  ;D

IS would not hurt, even on f/1.4 lenses. Not everyone shoots them fully open ALL the time. Sometimes a bit more DOF is desirable. Or 2 stops closed (f/2.8) for IQ. etc.

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Re: Why do fast primes not have IS?
« Reply #27 on: June 25, 2014, 06:17:17 AM »

endiendo

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Re: Why do fast primes not have IS?
« Reply #28 on: June 25, 2014, 06:40:48 AM »
I think people want absolutely IS, but don't know why..

Cameras have good higher and higher ISO..
Very good lens have a lot of light...

-> you can have enough light for fast speeds (> 1/100 or 150)... So why do we bother for IS....
I was useful when camera couldn't go (good) over ISO400..  but know, IS is more and more useless.

I see utility only for long lenses.
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GMCPhotographics

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Re: Why do fast primes not have IS?
« Reply #29 on: June 25, 2014, 06:41:05 AM »
I have a 400mm f2.8 LIS. It's a fast prime and it's got an image stabiliser.
I have a 24mm f1.4 L, it doesn't need and IS unit because it can be shot hand held at 1/25th second easily and due to it's huge light gathering capabilities, it can shoot at light levels several stops below what an f2.8 lens can achieve. So what could an Is offer a 24mm f1.4? Very little.

2 stops [2.8 - 2.0 - 1.4]  ... to be precise.  ;D

IS would not hurt, even on f/1.4 lenses. Not everyone shoots them fully open ALL the time. Sometimes a bit more DOF is desirable. Or 2 stops closed (f/2.8) for IQ. etc.

If i wanted sharp stopped down photos I'd use a 24-70IIL.
An is usint would only degrade IQ at f1.4 by introducing extra glass elements into the lens forumla. I was my farst primes as sharp as possible wide open....if not then there's little point to it. if you are going to stop down, then there's no need for a bag od heavy fast primes...a 16-35 and a 24-70 would be lighter, more versatile and cheaper.

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Re: Why do fast primes not have IS?
« Reply #29 on: June 25, 2014, 06:41:05 AM »