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Thread: EF-S lens outperforming EF L-lens?

  1. #41

    Default Re: EF-S lens outperforming EF L-lens?

    that is the reason for spot mettering
    metal, glasses, plastic and a eye to see

  2. #42

    Default Re: EF-S lens outperforming EF L-lens?

    Good thread, interesting discussion! Read from start to end.

  3. #43

    Default Re: EF-S lens outperforming EF L-lens?

    Shinobi, for the fun of it, i did the same test as you did. I have both 17-85 and 24-105 with 40D. it doesn't matter which focal length you use. the results are the same. the 24-105L will be slightly slower then the 17-85. I have both lens and using a 40D. But what is very important is you must aim at the same exact pin point spot to get equal metering on your camera. but having said all that, both lens are different. the same settings you "force" on both camera gives you the shutter speed but the image turns out quite differently. for the fun of it, i tried a 50mm f1.8 lens. you want to know the result @ 50mm? it's slightly faster.

  4. #44

    Default Re: EF-S lens outperforming EF L-lens?

    Quote Originally Posted by lukeeong View Post
    Shinobi, for the fun of it, i did the same test as you did. I have both 17-85 and 24-105 with 40D. it doesn't matter which focal length you use. the results are the same. the 24-105L will be slightly slower then the 17-85. I have both lens and using a 40D. But what is very important is you must aim at the same exact pin point spot to get equal metering on your camera. but having said all that, both lens are different. the same settings you "force" on both camera gives you the shutter speed but the image turns out quite differently. for the fun of it, i tried a 50mm f1.8 lens. you want to know the result @ 50mm? it's slightly faster.
    Interesting.. It might be a calibration problem with the factories which makes the lenses. I think they probably don't use the same factory for both of these lenses. Otherwise, it's probably calibrated towards what a professional photographer would look for vs what a consumer would look for.

    Best is to get an incident light meter to meter and then see which lens gives a correct 18% grey luminance reading when shot at the prescribed exposure value under controlled conditions.

  5. #45

    Default Re: EF-S lens outperforming EF L-lens?

    Quote Originally Posted by lukeeong View Post
    Shinobi, for the fun of it, i did the same test as you did. I have both 17-85 and 24-105 with 40D. it doesn't matter which focal length you use. the results are the same. the 24-105L will be slightly slower then the 17-85. I have both lens and using a 40D. But what is very important is you must aim at the same exact pin point spot to get equal metering on your camera. but having said all that, both lens are different. the same settings you "force" on both camera gives you the shutter speed but the image turns out quite differently. for the fun of it, i tried a 50mm f1.8 lens. you want to know the result @ 50mm? it's slightly faster.
    sorry but could i check the following items?
    1) did you use spot metering?
    2) was the camera remove from the tripod?
    3) was a tripod used?
    4) is the area used a controlled light area?

    but it is interesting i guess. may i will try once i have the time.
    metal, glasses, plastic and a eye to see

  6. #46

    Default Re: EF-S lens outperforming EF L-lens?

    its on my manfrotto, did not remove camera, only change lens. no spot metering. i did this at night in my room with 2 warm lights on focusing on my luke-skywalker lego figurine. tried using both program mode and manual mode.

    i don't think it is calibration problem. I have two 24-105.

  7. #47

    Default Re: EF-S lens outperforming EF L-lens?

    Quote Originally Posted by lukeeong View Post
    its on my manfrotto, did not remove camera, only change lens. no spot metering. i did this at night in my room with 2 warm lights on focusing on my luke-skywalker lego figurine. tried using both program mode and manual mode.

    i don't think it is calibration problem. I have two 24-105.
    hmm. now it gets interesting. i go try my 2470 and 24105.
    metal, glasses, plastic and a eye to see

  8. #48

    Default Re: EF-S lens outperforming EF L-lens?

    Quote Originally Posted by lukeeong View Post
    its on my manfrotto, did not remove camera, only change lens. no spot metering. i did this at night in my room with 2 warm lights on focusing on my luke-skywalker lego figurine. tried using both program mode and manual mode.

    i don't think it is calibration problem. I have two 24-105.
    I mean calibration at different production lines. Your two 24-105 probably comes from the same line so should have the same calibration..

  9. #49

    Default Re: EF-S lens outperforming EF L-lens?

    Sorry I haven't had time to respond earlier. Thanks to all for the responses. Hugely enlightening (hopefully for many others too), and I'm glad we really got the discussion going.

    I've read up on T-stops recommended by tiduck. They're quite relevant for videography. Unlike F-stops which are measured by physical dimensions, T-stops reflect the actual "performance" of a lens, light-wise.

    ch3nyong, my earlier hypothesis was in fact about either the quality of filter or the number of lens elements. Unfortunately, all I was able to verify is that it wasn't a cheap-ass filter on the 24-105L, but without being able to physically bring the two lenses together again and do the test without filters, this is an inconclusive lead. My bad - I wasn't counting on being absolutely lab-controlled, it was a just-for-fun test that became more and more puzzling as I thought about it, which led to my initial post. I am happy to note though that lukeeong was able to replicate my results with the same models of lenses.

    However, I think there is merit to the discussion on how the number of lens elements could affect light transmission, as pointed out by weixing (btw, yes i did meddle in amateur astronomy about 10 years ago, and at that time, binocs with 98% light efficiency commanded a significant premium over 90% efficient binocs 'cos lens coating technology had not matured very much yet; i never went into astrophotography though, but i presume the same considerations must have applied) and alternatve (although it's more elements = more light being reflected, not refracted).

    My thoughts now, in relation to weixing's and KangS's points, is that the manufacturers may have stopped specifying the transmissivity of lenses as coating technology improved. The entry-level lenses of yester-year may have started with coatings that were far inferior to today's coatings. Therefore, when compared to their higher-end counterparts, the overall light efficiency may have been inferior. In that context, releasing information about the "light-efficiency" of a lens would have been useful in helping people decide between lenses. (It would make people more inclined to upgrade lenses.)

    However, it may be that the difference in transmissivity of individual coating layers on today's lens elements, whether high-end or low-end is much smaller (just a guess, but we are probably talking about 98% to 99.5% now whereas in the past it may have been 90% to 98% - anyone know what it actually is?). Accordingly, the bigger determinant of a lens' overall transmissivity would be the number of elements and therefore the number of air-glass interfaces. In this context, releasing information about transmissivity would effectively "penalise" all the high-end lenses in head-to-head comparisons, as they use more elements for good reason to correct for aberrations and other determinants of image quality. Unlike brightness where we can simply move down an f-stop or drag out the shutter, it is not possible to correct for a blur image at the time of exposure, so we certainly can't fault the manufacturers for taking this direction and prioritising other aspects of IQ over the measure of transmissivity. Would welcome thoughts on this.

    Fragnatic- I thought it's fluorite, not flourite. Flourite sounds like what you get if you take corn flour and pound it into a solid mass.

    Finally, thank you muvouser, Dream Merchant, StrifeYun, JLee, RockyBoy, ditikolon, et al. Glad that I'm not the only person who finds this intriguing. I know it ultimately does not affect image quality much, but this is just curiosity for curiosity's sake. And I guess as an electrical engineer (I still remember doing Maxwell's equations to calculate EM wave propagation across material interfaces in class; dielectric coatings can significantly improve this and prevent TIR; and yes, Dream Merchant - since Maxwell's are usually specified as differential equations, the solutions are usually quite complex) by training, the issue of transmissivity had some resonance.

  10. #50

    Default Re: EF-S lens outperforming EF L-lens?

    Quote Originally Posted by foxguy View Post
    u say the light gathering power of the 24-105 is poorer compare to 17-85.

    bro, bring your 17-85, and borrow a 24-105 and go to a evening open concert. first use your 17-85. shoot till you find your lens starts to hunt a lot, then change to 24-105 and try. Others i hope understands what i meant.
    i have both 24-105 and 24-70. i tried many lens too. i find that only prime lens would be better. 50 F1.4 :P
    i think this is besides the point. the hunting happens because the AF works off the max aperture. the 24-105 has a constant f/4 so it's going to have more light to work with, and will naturally hunt less than the 17-85, which will probably be straining at f/5.6 since you probably would be using the tele-end for a concert.

  11. #51

    Default Re: EF-S lens outperforming EF L-lens?

    [QUOTE=shinobi;3811341....so it's going to have more light to work with, ......QUOTE]

    that is the thing. 24-105 would have more light entering compare to 17-85. therefore back to the topic, the light entering would be different.
    metal, glasses, plastic and a eye to see

  12. #52
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    Default Re: EF-S lens outperforming EF L-lens?

    Quote Originally Posted by shinobi View Post
    Fragnatic- I thought it's fluorite, not flourite. Flourite sounds like what you get if you take corn flour and pound it into a solid mass.

    ooops! wrong spelling.. haha
    EOS 6D | GH4 | LX100 | HERO4

  13. #53

    Default Re: EF-S lens outperforming EF L-lens?

    [QUOTE=foxguy;3811435]
    Quote Originally Posted by shinobi;3811341....so it's going to have more light to work with, ......QUOTE

    that is the thing. 24-105 would have more light entering compare to 17-85. therefore back to the topic, the light entering would be different.
    Yes, but if you think of the analogy to a water gun and fireman's hose, what we're trying to do is compare two fireman's hoses to see which lets more water through, ceteris paribus - or keeping other factors constant.

    Comparing a 24-105mm at f/4 and a 17-85mm at f/5.6 like comparing a fireman's hose to a water gun. Of course the water gun is washed out by the competition.

    Actually, I think you should be more precise. The light intensity through an f/4 aperture is greater than that through an f/5.6 aperture, which is what the 24-105mm and 17-85mm use during AF hunting, respectively. This is almost a truism and referencing this truism is what I meant by "besides the point".

    What is interesting though, is that it could be that the amount of light (# of photons) through a 24-105mm at f/5.6 is more than the light through a 17-85 at f/4, and the factor to consider here is the smaller image circle cast by the short-back EF-S lens. This would certainly be the case if the 17-85 was meant only for a 1.6x FOVCF body (1.6x1.6 > 2), but maybe not if it could also work on a 1.3x FOVCF body (I forget if it is).

    So, since AF depends on light intensity not absolute quantity (and this is why you wouldn't put a linear polariser on a DSLR lens since it cuts off the intensity of light in one plane of polarisation), it is pretty safe to say that AF will always function better (and hunt less) on a lens set to f/A compared to one set to f/B, so long as A < B. This is a truism which is not the crux of our discussion.
    Last edited by shinobi; 29th February 2008 at 07:22 PM.

  14. #54
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    Default Re: EF-S lens outperforming EF L-lens?

    Quote Originally Posted by shinobi View Post
    So, since AF depends on light intensity not absolute quantity (and this is why you wouldn't put a linear polariser on a DSLR lens since it cuts off the intensity of light in one plane of polarisation), it is pretty safe to say that AF will always function better (and hunt less) on a lens set to f/A compared to one set to f/B, so long as A < B. This is a truism which is not the crux of our discussion.
    AF is done when at the lens' max aperture wad. u cant 'set' the aperture during AF.
    EOS 6D | GH4 | LX100 | HERO4

  15. #55

    Default Re: EF-S lens outperforming EF L-lens?

    Quote Originally Posted by Fragnatic View Post
    AF is done when at the lens' max aperture wad. u cant 'set' the aperture during AF.
    i was about to reply the same thing
    metal, glasses, plastic and a eye to see

  16. #56

    Default Re: EF-S lens outperforming EF L-lens?

    Quote Originally Posted by weixing View Post
    Hi,


    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.
    wrong... the more important fact is that it is just a tool... and people are always worrying so much about their equipment, rather than concentrating on their skills in getting a better picture

  17. #57

    Default Re: EF-S lens outperforming EF L-lens?

    Quote Originally Posted by Fragnatic View Post
    AF is done when at the lens' max aperture wad. u cant 'set' the aperture during AF.
    Oops, yes my bad. What I meant is a lens whose max aperture is f/A will always have an advantage during AF compared to a lens whose max aperture is f/B, if A < B.

  18. #58
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    Default Re: EF-S lens outperforming EF L-lens?

    Quote Originally Posted by shinobi View Post
    Oops, yes my bad. What I meant is a lens whose max aperture is f/A will always have an advantage during AF compared to a lens whose max aperture is f/B, if A < B.
    yup!

    but that's for AF, i dun suppose it will affect the metering?
    EOS 6D | GH4 | LX100 | HERO4

  19. #59

    Default Re: EF-S lens outperforming EF L-lens?

    It technically should not affect metering because even if the camera is metering the scene for two different maximum apertures from two different lenses, the final result should still be congruent. That's why it's called 'metering' in the first place... calculations are made by the camera to determine the best values for the impending photograph right?

    If we can completely rule out "parallax" error by the body per se, then it is very possibly the light efficiency of the lenses that causes the discrepancy, ceteris paribus of course.
    But as suggested from one or two of the threads above... there is probably a lot of complexity in the possibilities presented/yet to be presented.

    As a sidenote, it's nice to see that this thread is so filled with many "inner scientists" amongst us... hahahahaha!
    Last edited by ditikolon; 1st March 2008 at 02:35 PM.

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