Lens apertures are typically quoted using the mathematical relationship of focal length to aperture diameter. They do not tell you that a certain amount of light will come through the lens. That's why, as someone has already said, in the film industry they do not use the technical definition of aperture. Some lens models let in more light at f2.8 than others. Regardless of whether you understand how Canon produces the nominal f2 specification, at its widest aperture, this new 200 is reputed to transmit 2/3rds of a stop LESS light than the old 1.8 model. What it says on the box doesn't affect the fact of this matter, and the only way to test this theory is to shoot one lens at f1.8 and 1/500th and the other at f2 and 1/320th and see if the exposure looks the same. If it does, and from what many sensible people are saying, it will, then there is 2/3rds of a stop between them. I don't think I can make it any clearer than that.
Heh, no one is asking you to make it clearer. I fully understand what you're saying. But, my quesiton was did you test this theory out yourself? Has anyone here confirmed this? I'll have a 200 2.0 next week, but don't know anyone with a 200 1.8 to compare images with or do a test.
No matter what's reputed, F2 should be the same on both lenses and if it's not then we should hold Canon's feet to the fire.
I think the best way to quantify differences in light transmitted through two or more lenses is to use Exposure Values (EV), or as mentioned by Peter, T-stops. To me, it makes sense to say that the f/1.8 lens is 2/3 EV faster than the f/2 lens, not that it's 2/3 stops faster, because these "stops" are defined by geometry, not light transmission.
BuLLets wrote:
No matter what's reputed, F2 should be the same on both lenses and if it's not then we should hold Canon's feet to the fire.
Well in that case we better start a class action against every single lens maker, because they all vary. For example, f2 on an Olympus OM 28 f2 is something less than half a stop brighter than f2.8. What's more, all these lenses have fall-off in varying degrees. Which part of the frame are you taking your consumer rights EV measurement from? The corner can be as much as 2 stops darker than the centre, or sometimes even more. F2 means what it always did: a ratio between focal length and aperture diameter. It has never guaranteed a particular number of candelas in any particular part of the frame. I'm surprised this is so controversial.
jcolwell wrote:
To me, it makes sense to say that the f/1.8 lens is 2/3 EV faster than the f/2 lens, not that it's 2/3 stops faster, because these "stops" are defined by geometry, not light transmission.
If it's geometric, then make sure you don't use it to discuss shutter speeds.
I take stops to mean increments on a base two scale, i.e. doubling or halving the consecutive values, whether they be aperture areas, shutter duration, or light levels. Bearing in mind the various ways that the required stop can change, with changing light or settings, it seems to make perfect sense to say the bride is 2 stops darker in the chancel than in the transept. I'll keep saying stops, thanks, as in, the 200 f2 transmits 2/3rds of a stop less light than the 1.8, although I agree that 'EV' is an equally good way of describing the scale.
This is all water under the bridge for most of us. The f/1.8 is gone, the f/2.0 is available so anyone that wants a new lens is stuck...
What I want to see is the $6k Canon go head to head with the $4k Nikon. What's a few thousand dollars? Buy a 200mm f/2 VR from Nikon and get a free D300 and a 1.4x TC... Don't tell me that isn't a tempting offer.
Hey brainiac that's a great idea. Another class action law suit to fill lawyers pockets with cash. Maybe you can get this started for us, what do you think?
Last I checked here in the states we don't have a lens 'consumer rights' agency, it must be great that you guys have one over there!
Thanks for the 411!
brainiac wrote:
Well in that case we better start a class action against every single lens maker, because they all vary. For example, f2 on an Olympus OM 28 f2 is something less than half a stop brighter than f2.8. What's more, all these lenses have fall-off in varying degrees. Which part of the frame are you taking your consumer rights EV measurement from? The corner can be as much as 2 stops darker than the centre, or sometimes even more. F2 means what it always did: a ratio between focal length and aperture diameter. It has never guaranteed a particular number of candelas in any particular part of the frame. I'm surprised this is so controversial. ...Show more →
...and don't forget that if you have a macro lens then 1:2 at f2.8 is often way darker than infinity. So transmitted light varies with focussing too. Canon's labelling of this lens as f2, even though it's not as bright as some other lens at f2, is perfectly correct. You can't expect them to break with a thoroughly entrenched tradition and start specifying lenses in a way that nobody else does. Do you prefer lumens, candelas or Trolands? Which frequency of light should be used? And which parts of the image circle should be specified and at what focussing distances? Centre, 10mm and 20mm would probably suffice. I can't see it happening soon.
jamesf99 wrote:
What I want to see is the $6k Canon go head to head with the $4k Nikon. What's a few thousand dollars? Buy a 200mm f/2 VR from Nikon and get a free D300 and a 1.4x TC... Don't tell me that isn't a tempting offer.
James69, that would be an interesting comparo to nourish the deprived souls of that recent FM crop of Canon-Nikon switchers, flame throwers-fanners and kindred fora conflagrators.
However, for many a 200 f/1.8 owner the internecine comparo should come first: 200 f/1.8 vs. 200 f.2 IS.
PetKal wrote:
James69, that would be an interesting comparo to nourish the deprived souls of that recent FM crop of Canon-Nikon switchers, flame throwers-fanners and kindred fora conflagrators.
However, for many a 200 f/1.8 owner the internecine comparo should come first: 200 f/1.8 vs. 200 f.2 IS.
There's already a direct comparison posted somewhere. if it hasn't been listed here in a previous thread, try photodo or one of those places. The f/2.0 out resolved the f/1.8.
it's all moot for me. I simply can't justify that FL right now (for any reason), so I guess that's good for my wallet.
PS - if no one is left alive after this to-the-death blood feud over minutia, I'll take somebody's lens from their widow. She, or they, can contact me here...
jamesf99 wrote:
There's already a direct comparison posted somewhere. if it hasn't been listed here in a previous thread, try photodo or one of those places. The f/2.0 out resolved the f/1.8.
If you are referring to the Digital Picture Com.'s ISO charts, I have seen those for both lenses.
There was also somethingh on a Hong Kong photo forum which only told me what I kinda knew already from the first principles: the 200 f/1.8 diffuses backround a bit more at f/1.8 than what the 200 f/2 could ever do.
DoubleNegative wrote:
I'd just like to add that if your f/2 breaks, it's under warranty. If your f/1.8 breaks, you're SOL.
Good point, Nancy.
One can often see that folks who have not experienced a problem with the 200 f/1.8 yet tend to think dismissively, if at all, about maintainability difficulties with that lens.
brainiac wrote:
...and don't forget that if you have a macro lens then 1:2 at f2.8 is often way darker than infinity. So transmitted light varies with focussing too. Canon's labelling of this lens as f2, even though it's not as bright as some other lens at f2, is perfectly correct. You can't expect them to break with a thoroughly entrenched tradition and start specifying lenses in a way that nobody else does. Do you prefer lumens, candelas or Trolands? Which frequency of light should be used? And which parts of the image circle should be specified and at what focussing distances? Centre, 10mm and 20mm would probably suffice. I can't see it happening soon....Show more →
You can't use the macro lens as an example as it is well known the true f-stop is not what's indicated when at macro distances and is related to the magnification times the indicated f-stop if I recall it's F*(m+1) where m is the magnification and the darkening arises from the internal shortening of the lens moving the rear element away from the sensor.
I doubt the extra elements account for a 1/3 stop lower light transmission than the f/1.8 version. With 5 extra elements and using a worst case coating that loses 1% light at each extra interface and assuming there are 11 interfaces you can show the effective aperture of the f/2 lens is at worst ~ 2.066, so more like a tenth of a stop.
Certainly 200/2 LIS is a wonderful lens, and I'd love to have one myself.
But there is something in 1.8 photos that I haven't seen in photos by 2.0 version. The "magic" found in 1.8 seems gone with the new one, at least from the photos i seen so far on internet.
Thanks for taking the time to post these shots, love to see real examples...so much better than speculative "text" reviews, give me photos every time! Great stuff!
jxsq wrote:
Certainly 200/2 LIS is a wonderful lens, and I'd love to have one myself.
But there is something in 1.8 photos that I haven't seen in photos by 2.0 version. The "magic" found in 1.8 seems gone with the new one, at least from the photos i seen so far on internet.
Any others feel the same?
I think thats because we have not gone out to shoot some real action shots, most of the shots are just test shots in difficult lighting situations. Its winter here, its wet and gloomy
Here is one that I handheld and taken at F2, its indoor and subject is close to darkish background as well.
pcho wrote:
I think thats because we have not gone out to shoot some real action shots, most of the shots are just test shots in difficult lighting situations. Its winter here, its wet and gloomy
Here is one that I handheld and taken at F2, its indoor and subject is close to darkish background as well.
Perry
Take heart, Perry, there is as much "magic" in that portrait shot of yours as in any of the three 200 f/1.8 copies I have shot with or in images I've seen on the net.
Purely to test this lens you need to take a static subject, in controlled lighting, and wind.
Shoot it in raw, on a tripod, with a timed shot. Take 3-6 shots at each aperture the lens / camera supports at, every ISO, then repeat with the larger 500mm lens.
