EF-S lens outperforming EF L-lens?

[Fragnatic]

for people who are interested in such a light test.
you would need to have a laser, a resever and a stepper power system, fire the laser thru the glass and measure the light loss in terms of dB. i am sure most L are good due to the "Flo****"(dun remember the spelling) element in L lens.
any way, putting that aside, i find lens that can perform in the real to be "good", not lab test reslts or hypes generated by "information".

LENS ARE JUST A TOOL, ENJOY PHOTOGRAPHY.

Flourite

 

[Tumbleweed]

As an engineer in manufacturing, I have to say that there manufacturers cannot always or rarely produce a "perfect" product. All copies that come out of the manufacturing line is built to a certain tolerance. So the aperture of F5.6 +/- 0.33 f-stop may be acceptable to the manufacturer. So what if the 17-85 may be 1/3 brighter at F5.6 than the other lens or vice versa? To the manufacturer is acceptable and within it's manufacturing tolerance. Don't lose sleep over it.

 

[adamadam]

for people who are interested in such a light test.
you would need to have a laser, a resever and a stepper power system, fire the laser thru the glass and measure the light loss in terms of dB. i am sure most L are good due to the "Flo****"(dun remember the spelling) element in L lens.
any way, putting that aside, i find lens that can perform in the real to be "good", not lab test reslts or hypes generated by "information".

LENS ARE JUST A TOOL, ENJOY PHOTOGRAPHY.

Florence

 

[flipfreak]

Florence

from amk? :bsmilie:

 

[alternatve]

The 24-105L, being a constant aperture and a L lens, would have more elements then the 17-85 zoom. More elements = more light being refracted. Thus, a f/4 isn't standard on different lenses, but very close to. The ancient Canon 50mm f/0.95 is one good example, the "real" aperture is closer to f/1.2.

Samuel

 

[foxguy]

ok thanks everyone for remembering the name .

 

[lightning]

To TS, I think better not get the L lens...it is really bad and not worth...

 

[muvouser]

I support your initiation in this subject.

Some of people just dont understand where you coming from and insist why bother.

From an engineering point of view, it is indeed a little puzzling.

The next question is if you take both shots, one lens at 1.8 and the other at 1/10. Would they be similarly exposed?

Fragnatic - to your point, I did choose 'outperforming' for a spot of sensationalism. But I think if I had used "more light-efficient than", I may not have gotten as colourful a comparison as lamborghinis and SUVs - really, care to explain this analogy?

But yes, maybe the experiment wasn't as tightly controlled as it could have been. (I really find it hard to explain why I would be standing slightly closer to the tripod every time I had the 24-105 mounted, and farther when the 17-85 was mounted though... *shrug*)

Not having an L lens in my inventory, I wanted to see if all things being equal, the L would have more action stopping potential than my other lenses - it turns out the answer is no (at least for the copies I had at the time). Actually I think there's a simpler answer to this, but I'll need to borrow that same lens again to double-check that hypothesis, so that will have to wait.

 

[foxguy]

To TS, I think better not get the L lens...it is really bad and not worth...

lol look at your signature lol.

but to TS, enjoy shooting and use what you find comfortable.
i truely think that is what that matters.

 

[weixing]

For the heck of it, I tested my EF-S 17-85mm f/4.0-5.6 IS USM kit lens on a 400D with a borrowed EF 24-105mm f/4.0L IS USM lens recently.

I mounted both lenses in turn on my camera, mounted on a tripod, and aimed it at a controlled indoor scene with both lenses set to 50mm focal length and stopped down to f/5.6. Then I metered the scenes, obtaining a shutter speed of 1/8 for the 24-105 and 1/10 for the 17-85.

What the? If anything I would have expected the much larger and more expensive L lens to be more light efficient and meter a faster shutter speed! I don't know how to explain this - sure, the 24-105 is older than my kit lens... but when we compare lenses we usually say the f/2 is brighter or faster than the f/4 etc... That's true in one sense, i.e. the f/2 can theoretically capture 4 times as much light as the f/4, but ONLY if you open it up. Are we missing some quantity associated with efficiency of light transmission through the entire lens?

To me, it seems that for some reason the L lens is less light efficient than the non-L lens. Under low-light of course it would win because it has the extra stop or so to play with if I used it wide open, but what if I was hand-holding, in relatively low-light, and I cared about maximising my DOF and didn't want to use it wide-open? Wouldn't that mean that the non-L lens has an advantage?

Correct me if I'm wrong, but f-number is simply based on the ratio of the physical dimensions of aperture width to focal length, right? Is there another quantity which gives us a measure of the light efficiency of a lens? It seems to me this could be useful as a basis for comparison across lenses.

Any thoughts? I'm not too experienced as a photographer, and this issue is really bugging me, especially since it seems the L lens really ought to have nailed the non-L lens, and not vice versa, in this case.

Hi,
Just wonder did you go into Astronomy?? ha ha ha ;p

Anyway, theoretically when light enter from air to an uncoated lens, it can loose over 4% of light transmission in reflection and scattering per surface (one lens got 2 surface). This light loss will exponentially multiplied when adding more lenses. For example, a single uncoated lens will have light transmission of 92.16% (0.96x0.96) and 2 uncoated lens will have light transmission of 84.93% (0.96x0.96x0.96x0.96). This is the reason why you can see your reflection on glass windows if you are on the brighter side.

A single layer of anti-reflection coating can reduce the loss to 1.5% and a multilayers composed of different coatings (multi-coated) to as low as 0.25%.

So EF-S 17-85mm f/4.0-5.6 IS USM kit lens have 17 elements(34 surface) and EF 24-105mm f/4.0L IS USM lens have 18 elements(36 surface). I assume both use the same fully multi-coated (coating on all surface of lens) standard (assume of light transmission 99.75% per surface), so the light transimission of EF-S 17-85mm f/4.0-5.6 IS USM kit lens is 91.84%(0.9975^34) and EF 24-105mm f/4.0L IS USM lens is 91.38%(0.9975^36).

Base on the above assumption and theoretical calculation, the EF-S 17-85mm f/4.0-5.6 IS USM kit lens should have a very, very, very small advantage in light throughput over EF 24-105mm f/4.0L IS USM lens if both use the same coating standard.

BUT do you think canon will use the same expensive coating on both their 'L' lenses and normal lenses?? I doubt so. So if you ask me, I think the 'L' lenses should have the better coating over the normal lenses and should have better light transmission over the normal lenses. Then you might ask why you get such result?? I'll assume your test is done properly and consistently. One reason I can think of is the physical design and construction of both lenses:
The EF 24-105mm f/4.0L IS USM lens should have better light baffle than the EF-S 17-85mm f/4.0-5.6 IS USM kit lens. So your result might be due to more stray light entering the EF-S 17-85mm f/4.0-5.6 IS USM kit lens which "fool" the DSLR meter and give a faster shutter speed than the EF 24-105mm f/4.0L IS USM lens.

Anyway, the different of 1/8 and 1/10 is very small. There are more importance factor other than light-tranmission, such as optical quality of the lenses.

Just my S$0.02...

Have a nice day.

 

[lsisaxon]

Please. I think we're missing the point that I'm trying to focus discussion on, which is light efficiency. I'm certainly not naive enough to suggest that the L lens is getting beat on all fronts by the non-L, or even on any other measure of IQ. All I'm saying is that for some reason (more lens elements?), the L appears to transmit less light. There may therefore be cases where 2 lenses exhibit the exact same IQ characteristics, but one is less light efficient. If so, the more efficient and transparent lens would warrant a price premium right? How do we find objective data to test lenses on this metric?

What I'm saying is that the L lens (or at least that copy) was less light efficient than the non-L. And I've said it before and I will say it again, this admittedly adhoc experiment was repeated several times, i.e. (1) take out 17-85, put in 24-105, set to 50mm/5.6, meter shows 1/8. (2) take out 24-105, put in 17-85, set to 50mm/5.6, meter shows 1/10, (3) repeat from step (1) several times. I consistently got 1/8 and 1/10 every time respectively. Yes, it's a small difference, but certainly not beyond the precision of the camera's metering system to resolve. So the questions in my first para still remain. Appreciate some feedback on those, rather than critique of the "experiment" methodology. If you want to be clinical about it, I suggest you run your own tests. I have a feeling this is something that you'll find in many other pair-wise comparisons of lenses - the question I've repeated is simply: how do you measure this difference?

Filters on the lens? Aperture calibration? Colour transmission characteristics? There are so many other thing that affect the meter. Best to shoot with both lenses with the same body using same manual settings and then obtain the luminance level on the image using software. For all you know the reported f/5.6 may not be exactly f/5.6 on one of the lenses at 50mm and body is compensating for it based on the information from the lens CPU.

 

[Dream Merchant]

for people who are interested in such a light test.
you would need to have a laser, a resever and a stepper power system, fire the laser thru the glass and measure the light loss in terms of dB. i am sure most L are good due to the "Flo****"(dun remember the spelling) element in L lens.
any way, putting that aside, i find lens that can perform in the real to be "good", not lab test reslts or hypes generated by "information".

LENS ARE JUST A TOOL, ENJOY PHOTOGRAPHY.

Not all L lenses contain flourite.

Canon's top-of-the-line 70-200L f/2.8 IS does not contain flourite, but that may be a good thing - it's may be less vulnerable in heat extremes than lenses containing flourite. :bsmilie:

 

[StrifeYun]

hmmm, just thought of something... interesting read btw.

with both pictures taken with the difference lens, could you measure the brightness on both images if they are of same brighness so you know the 1/8 and 1/10 shutter spd is also accurate.

TS let us know ya ?

 

[JLee]

Interesting topic and discussion.

Btw off-topic a little, I've just made some comparison yesterday between 16-35 f2.8L II and 17-40 f4L (purchasing reason) and the 16-35 consistently exposed 1/3 brighter than the 17-40 in Av mode. From every focal length e.g. 17, 20, 24 & etc and aperture f4 to f16. The environment is showroom lightings, camera on tripod, MLU and cable release.

I'm just a hobbyist and not an engineer or technical expert, but found some similarities in terms of 1/3 exposure differences in this discussion. It doesn't bother me as I learned something new.

Happy shooting always

 

[KangS]

Hi,
Just wonder did you go into Astronomy?? ha ha ha ;p

Anyway, theoretically when light enter from air to an uncoated lens, it can loose over 4% of light transmission in reflection and scattering per surface (one lens got 2 surface). This light loss will exponentially multiplied when adding more lenses. For example, a single uncoated lens will have light transmission of 92.16% (0.96x0.96) and 2 uncoated lens will have light transmission of 84.93% (0.96x0.96x0.96x0.96). This is the reason why you can see your reflection on glass windows if you are on the brighter side.

A single layer of anti-reflection coating can reduce the loss to 1.5% and a multilayers composed of different coatings (multi-coated) to as low as 0.25%.

So EF-S 17-85mm f/4.0-5.6 IS USM kit lens have 17 elements(34 surface) and EF 24-105mm f/4.0L IS USM lens have 18 elements(36 surface). I assume both use the same fully multi-coated (coating on all surface of lens) standard (assume of light transmission 99.75% per surface), so the light transimission of EF-S 17-85mm f/4.0-5.6 IS USM kit lens is 91.84%(0.9975^34) and EF 24-105mm f/4.0L IS USM lens is 91.38%(0.9975^36).

Base on the above assumption and theoretical calculation, the EF-S 17-85mm f/4.0-5.6 IS USM kit lens should have a very, very, very small advantage in light throughput over EF 24-105mm f/4.0L IS USM lens if both use the same coating standard.

BUT do you think canon will use the same expensive coating on both their 'L' lenses and normal lenses?? I doubt so. So if you ask me, I think the 'L' lenses should have the better coating over the normal lenses and should have better light transmission over the normal lenses. Then you might ask why you get such result?? I'll assume your test is done properly and consistently. One reason I can think of is the physical design and construction of both lenses:
The EF 24-105mm f/4.0L IS USM lens should have better light baffle than the EF-S 17-85mm f/4.0-5.6 IS USM kit lens. So your result might be due to more stray light entering the EF-S 17-85mm f/4.0-5.6 IS USM kit lens which "fool" the DSLR meter and give a faster shutter speed than the EF 24-105mm f/4.0L IS USM lens.

Anyway, the different of 1/8 and 1/10 is very small. There are more importance factor other than light-tranmission, such as optical quality of the lenses.

Just my S$0.02...

Have a nice day.

That sounds about right. I think .... :sweat:

Anyway, a long time back there was this additional component for lenses known as 'transmisivity'. Besides the normal MTF50 charts.

Seems that somewhere down the line, it was lost or discarded over the years. :dunno:

 

[Rockyboy]

A good thread :thumbsup:
Worth my 5 minutes of reading...

 

[Ljung]

just try take some shots at manual settings (same f-stop, shutter speed, FL...) and compare the photos.
if no exposure difference, what the heck. (err... in second thought, might see some difference? influenced by resolution, saturation, resolving power.... difference between lens design?)

But very unlikely to have significant difference (in this case, between 1/8 and 1/10 s) if talking about handholdability difference or stopping subject movement different...

 

[Nel21]

For the heck of it, I tested my EF-S 17-85mm f/4.0-5.6 IS USM kit lens on a 400D with a borrowed EF 24-105mm f/4.0L IS USM lens recently.

I mounted both lenses in turn on my camera, mounted on a tripod, and aimed it at a controlled indoor scene with both lenses set to 50mm focal length and stopped down to f/5.6. Then I metered the scenes, obtaining a shutter speed of 1/8 for the 24-105 and 1/10 for the 17-85.

What the? If anything I would have expected the much larger and more expensive L lens to be more light efficient and meter a faster shutter speed! I don't know how to explain this - sure, the 24-105 is older than my kit lens... but when we compare lenses we usually say the f/2 is brighter or faster than the f/4 etc... That's true in one sense, i.e. the f/2 can theoretically capture 4 times as much light as the f/4, but ONLY if you open it up. Are we missing some quantity associated with efficiency of light transmission through the entire lens?

To me, it seems that for some reason the L lens is less light efficient than the non-L lens. Under low-light of course it would win because it has the extra stop or so to play with if I used it wide open, but what if I was hand-holding, in relatively low-light, and I cared about maximising my DOF and didn't want to use it wide-open? Wouldn't that mean that the non-L lens has an advantage?

Correct me if I'm wrong, but f-number is simply based on the ratio of the physical dimensions of aperture width to focal length, right? Is there another quantity which gives us a measure of the light efficiency of a lens? It seems to me this could be useful as a basis for comparison across lenses.

Any thoughts? I'm not too experienced as a photographer, and this issue is really bugging me, especially since it seems the L lens really ought to have nailed the non-L lens, and not vice versa, in this case.

From my opinion, there's no significant difference between 1/8s & 1/10s. I dont know how "controlled" actually is your indoor environment but if you like to analyse things like this, you better be damm specific.

I would suggest you to repeat your metering act with only ONE of the lense to see how repeatable is the result. I wont be surprise to see slight changes in the result.

Anyone who wants to dump their L because of low light transmittion, kindly PM me.

 

[ch3nyong]

Interesting doubt here I dont have much input here, but one question though, are both of the lenses have any filters on? Just curious, if any of you missed out this point...

Cheers!

 

[zveron]

I think Bro Fragnatic do hit the nail on the head with his reply. FOV would be more than enough to explain the slight different in the EV measure, if the EV is not taken with spot metering.

The FOV will vary from one zoom to other, even if they are both at 50mm. As TS do not have the photo for comparsion, we can all debate till the cow come home.