Can anyone explain this to me,zoom lenses?
Discussion
Posted recently on here about buying my first sort of 'good' camera.Went for a bridge camera,the Fujifilm sl1000 but took it back quite quickly(luckily there was a battery charger fault as a reason to return it!)as i just wasn't impressed at the quality when using the 50x zoom.
Now,mentioning this 50x(1200mm)zoom on the Fujifilm really made me think of something.Considering this 50x zoom is merely just a 'feature' that can be thrown in on a £300 camera,why does it take three or four grand thrown at Canon to do approximately the same thing with one of their lenses??Incidentally i ended up getting a Nikon d3100 with the standard lense and a 50-300mm lense,so far i love it!
Now,mentioning this 50x(1200mm)zoom on the Fujifilm really made me think of something.Considering this 50x zoom is merely just a 'feature' that can be thrown in on a £300 camera,why does it take three or four grand thrown at Canon to do approximately the same thing with one of their lenses??Incidentally i ended up getting a Nikon d3100 with the standard lense and a 50-300mm lense,so far i love it!
Anything above about X15/20 on a bridge camera is likely to be "sensor enlargement" In other words the camera takes a small part of the image on the sensor and blows it up to appear as the full frame size. The pixels are enlarged leading to the loss in quality. "Proper" zoom lenses magnify the image onto the full sensor size. The better quality you want - the more glass - the more money - Simples
rumpelstiltskin said:
Posted recently on here about buying my first sort of 'good' camera.Went for a bridge camera,the Fujifilm sl1000 but took it back quite quickly(luckily there was a battery charger fault as a reason to return it!)as i just wasn't impressed at the quality when using the 50x zoom.
Now,mentioning this 50x(1200mm)zoom on the Fujifilm really made me think of something.Considering this 50x zoom is merely just a 'feature' that can be thrown in on a £300 camera,why does it take three or four grand thrown at Canon to do approximately the same thing with one of their lenses??Incidentally i ended up getting a Nikon d3100 with the standard lense and a 50-300mm lense,so far i love it!
You've answered your own question, there.Now,mentioning this 50x(1200mm)zoom on the Fujifilm really made me think of something.Considering this 50x zoom is merely just a 'feature' that can be thrown in on a £300 camera,why does it take three or four grand thrown at Canon to do approximately the same thing with one of their lenses??Incidentally i ended up getting a Nikon d3100 with the standard lense and a 50-300mm lense,so far i love it!
rumpelstiltskin said:
Now,mentioning this 50x(1200mm)zoom on the Fujifilm really made me think of something.Considering this 50x zoom is merely just a 'feature' that can be thrown in on a £300 camera,why does it take three or four grand thrown at Canon to do approximately the same thing with one of their lenses??
Massive amounts of glass. Quite literally.More glass = better image (lets in more light). Better glass = better image.
The bridge cameras can achieve 50x by using very small bits of glass. Quality is kinda meaningless at this point as it's so small.
But when you get to SLR territory the amount and quality of the glass becomes a major component in cost.
covboy said:
Anything above about X15/20 on a bridge camera is likely to be "sensor enlargement" In other words the camera takes a small part of the image on the sensor and blows it up to appear as the full frame size. The pixels are enlarged leading to the loss in quality. "Proper" zoom lenses magnify the image onto the full sensor size. The better quality you want - the more glass - the more money - Simples
I've seen this mentioned previously, it may even have been yourself in another thread - do you have anything to quantify your 15-20x zoom remark?What you seem to be describing, is digital zoom, which is a feature that can be turned off, and which is an entirely different kettle of fish.
There's nothing I can see in the Fuji website that alludes to the 50x zoom being comprised of part optical, and part digital - a wholly optical zoom is plausible due to the sensor size in these types of cameras.
Similarly the same would apply to the Canon and Sony, as well as Nikon.
My Fuji X-S1 has the largest sensor in a superzoom bridge, iirc, at 2/3" (exactly the same as the X10's), and is equipped with a 26x optical zoom, as well as 2x digital zoom, giving 52x zoom (1248mm equivalent).
http://www.youtube.com/watch?v=AgNJ-gOOqxY - skip to 3:33
The fuji has to cover a sensor sized 1/2.3 (i.e. the smallest on that pic.
An SLR covers a huge amount more and requires a lot more glass.
The fuji in actuality covers 4.3mm to 210mm range with a tinny image circle and poor quality optics.
The whole point of an SLR is to get as good an image as possible not to have a zoom lens that covers every focal length but provides unusable images.
The thing I've never understood about zoom lenses, and which nobody has ever really been able to explain is why expensive zooms tend to have fixed maximum apertures?
To keep the maths simple, let's assume we have a 100-200mm f2/8 lens. To provide for an aperture of f2.8 at the 200mm end, the lens has to be able to physically open out to the equivalent of f1.4 at the 100mm end, so why don't we get a 100-200mm f1.4-2.8 lens?
Surely logic would dictate that the cheaper the lens, the less likely this would be to happen, not the other way round?
To keep the maths simple, let's assume we have a 100-200mm f2/8 lens. To provide for an aperture of f2.8 at the 200mm end, the lens has to be able to physically open out to the equivalent of f1.4 at the 100mm end, so why don't we get a 100-200mm f1.4-2.8 lens?
Surely logic would dictate that the cheaper the lens, the less likely this would be to happen, not the other way round?
You'll have to educate me on the maths you're trying to keep simple.
But how does something open out physically to an equivalent?
If it doesn't open to f1.4, then there must be a glass co-efficient which mimics the f stop - but as this is at the long end, how would that work at the short end?
But how does something open out physically to an equivalent?
If it doesn't open to f1.4, then there must be a glass co-efficient which mimics the f stop - but as this is at the long end, how would that work at the short end?
Kermit power said:
The thing I've never understood about zoom lenses, and which nobody has ever really been able to explain is why expensive zooms tend to have fixed maximum apertures?
To keep the maths simple, let's assume we have a 100-200mm f2/8 lens. To provide for an aperture of f2.8 at the 200mm end, the lens has to be able to physically open out to the equivalent of f1.4 at the 100mm end, so why don't we get a 100-200mm f1.4-2.8 lens?
Surely logic would dictate that the cheaper the lens, the less likely this would be to happen, not the other way round?
Not sure I'm understanding you. When the zoom moves out you are essentially narrowing the tunnel that the light comes down, hence the f stops start to reduce, you are reducing the total amount of light into the lens itself.To keep the maths simple, let's assume we have a 100-200mm f2/8 lens. To provide for an aperture of f2.8 at the 200mm end, the lens has to be able to physically open out to the equivalent of f1.4 at the 100mm end, so why don't we get a 100-200mm f1.4-2.8 lens?
Surely logic would dictate that the cheaper the lens, the less likely this would be to happen, not the other way round?
An expensive lens may not have a reducing f-stop because of the internal construction of the lens groupings inside that allows the same amount of light to be let in regardless of where the zoom is.
On something like the Tok 11-16, I'm assuming that it's 2.8 throughout because of the short zoom in the first place, it may even be f2.4-3 in fact, but it just reports f2.8 to the camera throughout the range.
Edited by JDRoest on Monday 8th April 02:03
PJ S said:
I've seen this mentioned previously, it may even have been yourself in another thread - do you have anything to quantify your 15-20x zoom remark?
What you seem to be describing, is digital zoom, which is a feature that can be turned off, and which is an entirely different kettle of fish.
There's nothing I can see in the Fuji website that alludes to the 50x zoom being comprised of part optical, and part digital - a wholly optical zoom is plausible due to the sensor size in these types of cameras.
Similarly the same would apply to the Canon and Sony, as well as Nikon.
My Fuji X-S1 has the largest sensor in a superzoom bridge, iirc, at 2/3" (exactly the same as the X10's), and is equipped with a 26x optical zoom, as well as 2x digital zoom, giving 52x zoom (1248mm equivalent).
http://www.youtube.com/watch?v=AgNJ-gOOqxY - skip to 3:33
You're right now I've checked the camera spec it is a 50x Optical zoomWhat you seem to be describing, is digital zoom, which is a feature that can be turned off, and which is an entirely different kettle of fish.
There's nothing I can see in the Fuji website that alludes to the 50x zoom being comprised of part optical, and part digital - a wholly optical zoom is plausible due to the sensor size in these types of cameras.
Similarly the same would apply to the Canon and Sony, as well as Nikon.
My Fuji X-S1 has the largest sensor in a superzoom bridge, iirc, at 2/3" (exactly the same as the X10's), and is equipped with a 26x optical zoom, as well as 2x digital zoom, giving 52x zoom (1248mm equivalent).
http://www.youtube.com/watch?v=AgNJ-gOOqxY - skip to 3:33
Perhaps the OP just bought a crap camera
JDRoest said:
Kermit power said:
The thing I've never understood about zoom lenses, and which nobody has ever really been able to explain is why expensive zooms tend to have fixed maximum apertures?
To keep the maths simple, let's assume we have a 100-200mm f2/8 lens. To provide for an aperture of f2.8 at the 200mm end, the lens has to be able to physically open out to the equivalent of f1.4 at the 100mm end, so why don't we get a 100-200mm f1.4-2.8 lens?
Surely logic would dictate that the cheaper the lens, the less likely this would be to happen, not the other way round?
Not sure I'm understanding you. When the zoom moves out you are essentially narrowing the tunnel that the light comes down, hence the f stops start to reduce, you are reducing the total amount of light into the lens itself.To keep the maths simple, let's assume we have a 100-200mm f2/8 lens. To provide for an aperture of f2.8 at the 200mm end, the lens has to be able to physically open out to the equivalent of f1.4 at the 100mm end, so why don't we get a 100-200mm f1.4-2.8 lens?
Surely logic would dictate that the cheaper the lens, the less likely this would be to happen, not the other way round?
An expensive lens may not have a reducing f-stop because of the internal construction of the lens groupings inside that allows the same amount of light to be let in regardless of where the zoom is.
On something like the Tok 11-16, I'm assuming that it's 2.8 throughout because of the short zoom in the first place, it may even be f2.4-3 in fact, but it just reports f2.8 to the camera throughout the range.
So, a 100mm lens at f2.8 = 35.71mm, at f16 = 6.25mm, at f22 = 4.55mm and so on?
Now, assuming that's correct, we know that at 100mm our lens has to be able to open out to 35.71mm to provide that f2.8 number. If you apply that to a 50-100mm zoom, then at the 50mm end, that same 35.71mm - which we already know the lens can physically do - is f1.4 rather than f2.8.
This being the case, I would've thought the more expensive the lens, the more effort would be made to make maximum use of this fact, so you might expect to see a Canon 50-100mm f1.4-2.8 L, for example, whereas in reality it's the cheapest zoom lenses which tend to do this. I guess there must be a reason, but it seems counter-intuitive to me? Even if f1.4-2.8 is off the cards because it would be demanding too much of a compromise somewhere else in the lens manufacture, I would've thought they could deliver up f2-2.8 or something?
Frik said:
Would an F2-2.8 range in the lens really be more useful than having a constant F2.8 maximum aperture throughout the range?
Why would f2 not be better than f2.8, assuming image quality doesn't suffer? 
People pay £82 for a Canon 50mm f1.8, £269 for a 1.4 and £1,099 for a 1.2. Yes, there's extra build quality and the like in there as well, but if you wouldn't want the 1.2, why pay for it?
Is there something different about zoom lenses which would prevent you from wanting the widest aperture you can get at every point in its range?
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