How can I work around metering issues with adapted lenses on a Canon DSLR?

Question

I have a bunch of Contax lenses (C/Y mount) and a mount adapter with "dandelion" chips. This should allow me to use my lenses on any Canon DSLR using aperture mode and stopping down the lens. Thanks to the chips I also have focus confirmation.

However, I have metering problems. Wide open it's ok but when I close the lenses I get overexposure (this is aperture dependent).

I have performed tests on the 50D, 5D MII, and 600D. They all present this problem as if the metering was unable to work in low light (with the lenses stopped down). The problem is present for all the lenses I tested (50mm 1.7, 80mm 1.4, 135mm 2.8). Overexposure may reach 2.5 stops with the 80mm totally closed on a 5D while wide open the metering is ok.

Has anyone else also encountered this problem?

Is there an explanation (I mean, there is no coupling: the body does not know if the lens is wide open or stopped down) for how the metering can be off in one case and not in the other one?

Is there any known workaround (apart from a table giving the correction according to the f-number)?

Asked by floqui

Answer

Canon cameras (as most DSLR cameras these days) meter and AF wide-open. There is a limit on the maximum aperture wherein metering and AF can perform properly, and a cutoff where they are unlikely to work at all. In modern Canon cameras, the metering sensor is up in the viewfinder housing, just above the eyepiece you look through. At narrower apertures (lets say smaller than f/8), the amount of light lost between the primary mirror, the focusing screen and the pentamirror/pentaprism is probably so much that the metering sensor has too little light to work with (well less than 50% of the light that originally entered the lens).

Metering sensors are usually rated in a range of exposure values. I think all of the cameras you listed are rated to work between 1 - 20EV and a certain temperature (roughly room temperature, although the exact value sometimes changes from camera to camera.) The 5D II might actually work from 0-20EV. Top-end professional grade cameras and newer mid-grade professional cameras can operate from -1 or even -2 EV up through 20 or more EV, and therefor have up to three stops more low-light metering capability than your average entry-level.

If you stop down your Contax lenses enough in poor enough scene lighting, you might be reducing the EV at the metering sensor below the minimum of its operating range. Since the metering sensor is designed to operate wide open, before an electronic aperture is stopped down for exposure, if you are working in weak light with a stopped-down manual aperture, you'll make it even harder for the metering sensor to operate correctly. You might simply try half-pressing the shutter with the aperture wide-open, meter, use the AE-Lock function to lock in exposure, stop down, and fully press the shutter button to take the photo at the previously metered settings.

Answered by jrista

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Can I use an old Olympus-mount lens on a Canon DSLR?

Question

What is the mount adapter I need to mount a Vivitar 28mm 1:2 No.22 (made by Kino, aka Kiron) lens on my Canon 600D? Is it the T/T2 lens mount?

I used to mount this lens on my dad's Olympus OM-10.

Asked by Akram Mellice

Answer

No. (I should clarify that. I mean, "no, that's not the right adapter." The answer to the underlying question, "can I use an Olympus OM-mount lens on my Canon EF-mount camera," is clearly, "yes.")

The T-mount lens is a screw-mount type introduced by Tamron as a universal mount (to be used with adapters to fit the various camera brands), and is a sort of precursor to their later Adaptall/Adaptall2 mount system. These days, the T-mount system is used mostly as an interface between cameras and other optical systems, like telescopes, microscopes and binoculars (using only one of the two optics, of course).

You would need an OM to EF adapter, like the Photodiox model listed here. Luckily, the OM mount had one of the longest flange-to-film distances ever, so the adapter is just a simple bit of metal with no additional optics, and will still allow infinity focus. Whether the adapted lens will work on your camera depends on whether your camera allows lenses with no electronic linkage to speak of to work (it varies by model—check your manual).

Answered by Stan Rogers

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What Nikon F lenses can be adapted for micro four-thirds cameras and with what limitations?

Question

There seem to be several makes of adapter that allow most Nikon F lenses to be mounted on any Micro four-thirds (M43) camera.

I believe that autofocus is not supported, nor is electronic aperture control.

I have several categories of Nikon F lenses, for example

• AIS (e.g. micro 55mm f2.8)
• AF-D (e.g. 50mm f1.8)
• DX G (e.g. 18-200mm VR)

Which of these lens types can I use on an M43 camera and in which metering modes

• Aperture priority?
• Fully manual - no metering at all?
• Something else?

Answer

You're right, autofocus and aperture control are not supported (at least not in normal adapters like the ones you find on ebay or amazon). That means you'll need a lens with aperture and focus rings. That's the only restriction afaik. Shoot in Aperture mode, select the aperture at the lens and let the camera do the metering.

And find out if your camera has a focus assist function. On my E-PM1 i can reassign the red video button to do that. One push and the center of the image gets magnified, that makes exact focusing much easier.

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Is it worth it to buy an FD-EOS adapter, or is it better to exchange a misbought lens?

Question

I recently bought a manual-focus (since manual doesn't bother me) 100mm prime macro lens. However, I didn't notice at the time of purchase that it was an FD lens. (I'm a hobbyist; I didn't know Canon had actually changed lens mounts at some point.)

On the one hand, I kind of want to experiment with this guy. And quality FD lenses are relatively cheap on the used market, so if the adapters were worth it, I could probably get more (and more varied) glass. On the other hand, everything I read about the FD-EOS adapters is highly contradictory. As in, some people swear by them, and others think they're outright tripe.

I am still within the exchange period, and can easily exchange this lens for this 50mm prime that I'd been tossing up about buying anyway, as they are the same price.

Which would be the wiser choice?

Answer

Generally I'd say it's not worth trying to adapt an FD lens for the EF mount. The reason for this is that the EF mount has a larger registration distance, that is distance from the sensor the mount so that any simple FD to EF adaptor will act like an extension tube and you wont be able to focus beyond a few meters!

Canon produced an adaptor with a glass element which corrected focus distance but increased focal length by a factor of 1.1, could only be used with telephotos and decreased optical quality. This adaptor was mainly produced to placate those with a significant investment in long Canon glass and is quite rare. This is probably the reason people consider this type of adaptor to be "tripe". There are also third party versions of this adaptor which are comparable to the Canon one (i.e. still not that good).

However, as the lens in question is a macro lens, you could use a simple mechanical adaptor and the result would be a decrease in minimum focus distance, increasing magnification. So if you plan to use this lens for macro work then you should be able to adapt it no problem, however it wont be useful for anything else. A glassless adaptor wont compromise the optics so this is probably responsible for the mixed opinions on adaptors.

At the very least you need an adaptor with an aperture ring so you can stop down (almost essential for macro work) I think most of the glass ones do this, if you can't find a mechanical adaptor which will work the aperture for you, you can remove the glass from one of the other adaptors.

Incidentally, that 50 f/1.8 is well worth the price so I would leave it on the shopping list even if you keep the macro, for when you can afford it.

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Is there an adapter for Canon AE-1 lenses on Canon 550D?

Question

Is there a way to use my old Canon AE-1 lenses on my new EOS-550D?

Answer

Short answer: yes, but you won't like the results.

Longer answer: those old lenses sure are fun :) ... but you still won't like the results. Here are some details:

There are adapters, and you can by cheap glassless ones (that won't allow infinity focus -- they basically act like extension tubes) or adapters with glass to allow infinity focus but that have varying quality (depending on how much you are willing to pay -- Canon even made an extremely expensive official adapter, I've heard, decades ago to help pro photographers with the switch from FD to EOS).

Unfortunately, your quality will really suffer. When I got my 30D I bought a couple FD lenses (my crown jewel was a 135/2.8, beautifully small and responsive and light-weight) but in order to use them with my adapter I had to stop them down 2-3 stops in order to get good pictures without CA. I still loved using that 135, and in the right light I could still get a decent picture every once in a while at f/2.8, but for all practical purposes it was a 135/8 and it's hard to get excited about a 135/8 and want to take it out for pictures.

With the 135 and the glassless adapter, the maximum focus distance was about 6 feet. With a 100-300 at 300mm, the maximum focus distance was, oh let's say I was 15 feet from a house and I could just barely focus on something at the top of a two-story house so what's that, 25 feet? Somewhere around here there's also a question where I both calculated and experimentally determined the maximum focus distance of a 50mm lens with a glassless adapter (it wasn't pretty).

If I were you, I certainly wouldn't throw out your lenses: I'd spend a few dollars on a glassless adapter and consider spending a few more on an adapter with glass to allow infinity focus. You can use the glassless adapter to turn your wider-aperture lenses into macro lenses (I use one with a 35-70 f/3.5-4.5, but the smallish aperture makes focusing difficult and I'd like to get an f/2 or wider lens for that purpose), and the adapter-with-glass to run some experiments. But I'm sure that you'll get better pictures with a cheap all-plastic slow consumer modern lens (especially one with modern coatings, which also play a big part in image quality) that doesn't require an adapter than with your expensive-at-the-time fast lenses with an adapter.

I'm sorry to be the bearer of bad news... and if you can prove me wrong, I'd love to hear it!

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