Metering with an EOS and non EOS lens

On my EOS 630, if you have a Nikon lens mounted via adapter with chip or no lens at all, you can still scroll through f stops. Do you just set the f stop at f/1.0 to get a correct reading? I'm confused.

I don't think the f/stop you select on the body will matter. It's metering through the lens, at whatever aperture the lens is at, and selecting the aperture based on that. You're really just stop-down metering, aperture priority.

Since the camera can not control the lens aperture on a non-EF lens, you can not shoot in shutter priority.

Set the shooting mode to Av, select your aperture on the lens (stop down), then fire away. The camera is selecting the shutter speed based on what it sees as the amount of light coming in from the lens once you've selected your aperture.

Thanks but never mind. The camera malfunctions when the adapter is on. When you press the shutter, the mirror stays up, it doesn't advance, and BC(battery check) displays. I thought maybe the contacts for the chip on the adapter was causing it, so I removed the chip. But it still does it with the adapter on. I don't understand why-nothing touches the electrical contacts. With a EOS lens or no lens the camera fires just fine. So I guess I can't use the adapter with this body.

I had the same issue with my 630. It had two problems. One - I had to disable the backlight in the lcd screen to stop a battery draw. Two - Some adapters will not properly fit the mount. See this link for details on the adapters. http://photography-on-the.net/forum/showthread.php?p=14732043

I had the exact same problem with an adapter I got. I fixed it using the same information from the link. I leave my camera in the P mode and using the M 42 lenses with an adapter and the camera works perfect.

It functions like it is in aperture priority and meters perfectly.


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I fixed it. I grinded about 3mm of the bayonet mount at the 10 o clock position and now it doesn't push on the little switch. Now, back to the f stop. With the adapter and Nikon lens or no lens if you select a different f stop in manual mode your meter reading changes. In AV changing the f stop changes the shutter speed. But the amount of light coming in stays the same . Doing a quick test setting it to f/1.0 gives about the same reading as other cameras. Is that how it should be?

Here's an image showing what needed to be grinded with the Dremel tool.

f/16 said:

I fixed it. I grinded about 3mm of the bayonet mount at the 10 o clock position and now it doesn't push on the little switch. Now, back to the f stop. With the adapter and Nikon lens or no lens if you select a different f stop in manual mode your meter reading changes. In AV changing the f stop changes the shutter speed. But the amount of light coming in stays the same . Doing a quick test setting it to f/1.0 gives about the same reading as other cameras. Is that how it should be?

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Glad you got it fixed. Now, back to the aperture.

What's happening when you say

In AV changing the f stop changes the shutter speed. But the amount of light coming in stays the same .

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, is just the exposure triangle.Change one of the three (ISO/ASA, Aperture, or shutter speed), something has to make up the difference. The camera thinks "Oh, I see this much light, and the user has selected ASA XXX, and aperture X, therefore, using my programmed computer circuitry, I will use shutter speed1/XXX to make an exposure that when everything is blended together, we will get 18% grey." Now since on a film camera, you won't be changing the ASA, and the camera can't. So in Av (Aperture value priority automatic exposure), the only thing the camera is able/allowed to change is the shutter speed. So when you tell the camera "Camera, I want to change the aperture value I want to use to X.x", you're also telling the camera that you have given it permission to change the shutter speed as it sees fit to achieve what it believes to be the best exposure via shutter speed based on your input values of the ASA and the aperture value you have selected. So, even though the quantity of light hasn't changed, one of the three needed values has changed (aperture), so it adjusts the 'Time value' (aka shutter speed) up or down.

With any camera that has automatic metering (film or digital), if you are not using a lens that the camera can control, you have to shoot in stop-down metering mode. So you are using a Nikon lens adapted to fit (and that's all you've done is allow it to fit on the Canon), but the camera has no possible way of controlling any 'automatic' features of the lens (if any). So you now have to be an extension of the camera, and pick up where it is leaving off; controlling the aperture of the lens for the proper exposure. To get the proper exposure, the camera has to see the amount of light it will have available when the shutter is pressed. You do that by stopping down the lens to whatever f/stop you want to use, then let the camera meter, it will then see the amount of light, and then make it's decision on the shutter speed for the exposure.

What aperture value the camera is set at makes absolutely no difference in the final exposure when stop-down metering. If you tell it the aperture is f/1.0, and stop down to f/22, all the camera knows is that there is this amount of light hitting my exposure sensor, and it will decide the Tv based on the amount of light it sees, not on the aperture value you tell it. If anything, the camera will think to itself "Man, it must be really dark in here". Of course a camera doesn't actually think. You could tell it you are using f/32, and shoot wide open, it won't matter in the final image.

Put the lens on the camera. Leave the lens wide open at 1.8. Set the AE mode to Av, and take a reading with the Av on the camera at 1.8. Let's say it gives you a Tv of 1/100. Now, change the aperture on the lens to f/2.8 (1 1/3 stop less light), and your shutter speed will drop to somewhere around 1/40, which is (about) 1 1/3 stop slower, so it can allow the light a longer period of time to expose the film. And that's without touching the Av control on the camera. The amount of light the camera registered changed, therefore the Tv changed. Now, set the lens back to f/1.8, and this time change the camera's aperture setting to f/16. The shutter speed should stay the same. It will initially change, because it has the balance of the ASA, Av, and Tv in it's 'brain', but if you half press the shutter again, the shutter speed should return to what it was when it was set to f/1.8 (1/100).

Unless my brain is on vacation, I think all of that is correctly said. If not, I'm sure, and I hope, someone will be along to correct it.

Some adapters will push that switch in the EOS mount which then tells the camera that an EOS lens is fitted. If then the electronics can't figure out what is going on (which they won't as you don't have an EOS lens on) the camera locks up. This behaviour I think is on all film cameras up to the 1D or something like that, digital cameras newer than the 1D have no such switch.

So you either buy an adapter that does not trip the switch OR you buy an adapter that trips the switch and then you add one of those glue-on electronic contact patches.

See this:

Dead Link Removed

"Old and new stop-down metering styles. tells you about the metering.
"Camera locks up with the manual focus lens installed" tells you about the switch that locks up your camera.

If you are trying to use the auto focus confirm function on an adapter with a chip, open your aperture wide open to compose and achieve focus. The focus sensor needs a lot of light. When you achieve focus, then manually stop the aperture down to get the exposure you want. If if you are not using a auto focus confirm chipped adapter it is still easier to achieve focus and the composition you want with the aperture wide open.

Does use of a non-EOS lens on a chipped (or unchipped) adapter result in metering errors on a EOS film SLR, like I have found to happen on EOS dSLR?!

I dont have a dslr, but I get no metering errors on the 620, or 630. I will try my elan tonight


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trythis said:

I dont have a dslr, but I get no metering errors on the 620, or 630. I will try my elan tonight


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What I (and others) have experienced with EOS dSLR is that if you set camera on a tripod (for absolutely consistent framing, no deviation of metering due to different scene content) that if you put camera in Av mode and shift the aperture thru the range, the shutter speed that results is not a consistent -1EV of shutter speed for every +1EV of aperture. It seems that f/4 is the center of the range and deviation goes in both directions from there. That is,

• if the error is in the direction of underexposure, as you depart from f/4 the amount of underexposure increases as you deviate from f/4, or.
• if the error is in the direction of overexposure, as you depart from f/4 the amount of overexposure increases as you deviate from f/4.

One lens might lean in the direction of increasing underexposure (as you deviate from f/4), a different FL lens might lean in the direction of increasing overexposure, rather than all shots having same density!

So, in the test series, due to the adapter the non-EOS lens is stopped down to different apertures at the time of the metering, so the amount of light striking the meter is changing, and one would expect that the camera modifies the shutter speed suitably for the changing amounts of light. But it does not do it accurately.

I use the P mode not AV


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trythis said:

I use the P mode not AV


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Mode DOES NOT matter, in the metering error! Av or P or even manual, the error is there. Besides P vs. Av vs. manual are automation of SETTINGS, and has nothing directly to do with measurement of light (a.k.a. 'metering' (which is identical in all modes). Get your aperture to change while in P, and the deviation error will be seen (if film EOS are subject to the same errors as digital EOS)

My Elan IIe will meter with an adapter and an OM lens.

My 7N and 7Ne bodies will not.

wiltw said:

Mode DOES NOT matter, in the metering error! Av or P or even manual, the error is there. Besides P vs. Av vs. manual are automation of SETTINGS....

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I didn't mean to imply it did, just saying how I use mine.

The P setting flashes errors on my nikon F100 if a manual lens is attached to it and probably shoots in A mode but it doesnt say that. I know little about the eos system and was projecting the little i know about nikons and how they deal with different lens configurations. My N8O just will not meter at all with manual focus lenses of any kind, for example.


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