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Anyone here using baffles with their legacy lenses?

Discussion in 'Adapted Lenses' started by verbatimium, Apr 13, 2014.

  1. verbatimium

    verbatimium Mu-43 Veteran

    Jul 17, 2013
    Toronto, Ontario
    I was just curious whether anyone here uses and has had good results with using baffles on ~50mm f1.4 lenses to get better results wide open.

    The primary reason wide lenses aperture lenses have a "glow" effect or are not sharp/contrasty is because they are not designed for a digital sensor, which is very reflective when light strikes it at wide angles. This causes the light to scatter within the lens and back onto the sensor. Because most legacy lenses are full frame lenses and cast a much larger image circle than the m4/3 sensor, there is a lot of "unused" light that has a potential to scatter and lower the sharpness/contrast of the lens. If you cover the rear element with a black fabric enough so that the image circle produced by the lens just covers the m4/3 sensor, it should block out a lot of this stray light and improve contrast and sharpness of lenses, without affecting meter and the amount of light read by the sensor. This is similar to stopping down the aperture as you get sharper and higher contrast images with legacy lenses, however in this case, you are affecting the metering and the amount of light read by the sensor.

    I am thinking of trying it on some of my ~50mm f1.4 lenses and comparing them shot at f1.4 with or without a baffle on and compare contrast/sharpness..
  2. heli-mech

    heli-mech Mu-43 All-Pro

    Mar 9, 2012
    Vancouver Island, Canada
  3. speedandstyle

    speedandstyle Mu-43 Hall of Famer

    I have not tried baffles but I do know that under certain circumstances a lens hood helps a lot, even when you aren't shooting into a light source. The other thing I have noticed is that some adaptors are painted satin and not flat inside. This could account for some internal light reflection. I have also seen an adaptor or two leak light.
  4. RnR

    RnR Mu-43 All-Pro

    Sep 25, 2011
    Brisbane, Australia
  5. kwalsh

    kwalsh Mu-43 Top Veteran Subscribing Member

    Mar 3, 2012
    Baltimore, MD
    So actually this isn't true at all. It is said a lot on forums but is provably wrong. The actual cause is spherical aberration which is frequently present in legacy lenses (modern lenses use aspheric elements to correct better for it) and of course for a lens design for full frame the magnitude of the effect is doubled when magnified from the smaller m43 sensor. People do occasionally think they see improvement using baffles, unfortunately what has really happened is they made the baffle to small and have created a new aperture stop, thus stopping down the lens and reducing spherical aberration as it goes to the third power with aperture.

    You can't actually. A little geometry will show that any baffle even a small distance from the sensor has such a large penumbra because of the very large exit pupil of a wide aperture lens that you don't control stray light at all. You don't even need equations if you aren't good at math, just a pencil and a ruler and a piece of paper can show this.

    Except that most folks are. Everytime someone has claimed on these or the DPR forums in the past decade to have improved their legacy lens with a baffle once they do controlled tests it is found they actually effectively stopped down the lens. And in fact just stopping down the lens works better - moving the aperture stop inadvertently with a baffle actually makes overall aberrations worse than if you stopped down the proper aperture.

    By all means experiment! But measure your exposures carefully and you'll almost certainly find it doesn't work. I and some others over at DPR tested this extensively years ago and showed conclusively the baffles concept just doesn't work. I even ran one test with the Canon FD 50/1.4 where I made a baffle such that there was no change in aperture on axis but I did allow for some additional vignetting - in other words the tightest baffle possible without effectively stopping down the lens. In normal shooting - no difference. In contra light - no difference. With super bright lights just off-axis so they'd be off the sensor - no difference. And when I say no difference I don't mean just visibly - but measuring the RAW files too. No difference.

    There are some special cases in which a really horrible adapter has bright reflective surfaces in it - taming those can help a little. But you don't need a baffle in that case, just cover the reflective parts as best you can with something dark. But trying to make the image circle smaller on a legacy lens just doesn't work with baffles plain and simple (and sadly).
    • Informative Informative x 2
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  6. HarryS

    HarryS Mu-43 Top Veteran

    Jun 23, 2012
    Midwest, USA
    I have a bare generic OM adapter, and also the equivalent stacked combination of a well baffled Panasonic DMW-MA1 adapter and Olympus MF1. I see no visible difference using them with my 50mm f1.8 or a 28mm f2.
  7. gcogger

    gcogger Mu-43 Veteran Subscribing Member

    May 25, 2010
    That's exactly what I did when I tried it :redface: I initially thought it made a big difference, then realised I'd accidentally stopped down the lens! Once the baffle was (just) big enough then there was no difference with or without baffle.
  8. I prefer to use a hood or step-down ring over the front element to stop the additional light from entering the lens in the first place.
  9. kwalsh

    kwalsh Mu-43 Top Veteran Subscribing Member

    Mar 3, 2012
    Baltimore, MD
    Hoods are a great thing to use with most any lens that isn't very wide angle, legacy or not. Reducing off-axis light is a good thing. But as far as controlling stray light from the image circle as the OP is referring to again they don't actually help. They don't actually affect the image circle at all and by the time they do you get severe vignetting. What you've done at that point is created a new field stop for the lens (the field stop, different from the aperture stop, is what defines the image circle - it is sometimes a particular lens element and other times its own physical stop). Again, not desirable or very functional.

    Any lens hood that you attach to your lens really only blocks light rays that would never have a direct path to the rear of the lens in the first place, they are at a much steeper angle than that (again pencil and paper can show this pretty clearly). These rays instead could degrade the image by scattering off of internal parts of the lens or reflecting off of lens elements - basically classic off axis flare.

    You can do a test (and I have) with a "perfect" lens hood. It effectively extends all the way to the subject plane and is the exact size of the field of view of the sensor. You are blocking all non image forming light at this point. Sadly, as mentioned before, even this does nothing to reduce the loss of sharpness and contrast typical of wide open legacy lenses. Of course this kind of a hood isn't practical at all, but it is the best we could ever hope for and even it doesn't help.

    At the risk of going off topic - you can do some wacky things to lenses with hoods and baffles on purpose. Some lenses are known to exhibit "swirly bokeh" of which there are a variety of causes. One of the most obvious causes is a cat's eye exit pupil off axis from undersized or poorly located aperture or field stops. It turns out the optics of the 25/1.4 make it possible to easily create a new stop at the front of the lens to create this effect. It also causes additional vignetting of course, but that can be fixed in post. I did this experiment for fun on my 25/1.4, here are the results (normal followed by swirly):

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    Throwing stops and baffles around willy-nilly can do surprising things to a lens!
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  10. Itchybiscuit

    Itchybiscuit Photon Mangler

    Dec 10, 2013
    Glasgow, Scotland
    After reading the wealth of information on the dastardly properties of rogue photons, I'm truly baffled. :wink:
    • Funny Funny x 1
  11. 3dpan

    3dpan Mu-43 Veteran

    Mar 11, 2017
    Far North, New Zealand
    I would like to resurrect this thread.
    It has been 3 years since the last posting, and there may be further information on the subject.
    To me the idea of a baffle somewhere at the rear of the lens seems intuitively to be a good idea.
    Another question I haven't seen answered is should the baffle be at the rear of the lens or the adapter ?
    Any thoughts, opinions, facts would be welcome.
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