Solution for Canon overexposure with MF lenses?

[bobcominitaly]

For over a year I have been vexed by my 40d's unreliable metering when using MF lenses. I have chipped Nikon and M42 adapters, and wide open they give me a nice focus confirm and correct metering. The moment I go to a smaller aperture, my metering becomes unreliable - from 1 to 3 stops overexposure, depending on the lens and aperture chosen. I have discussed this last year in a thread, and it seems a fairly common problem.

I found out that this only happens when shooting through the viewfinder - in live view metering and exposure are fairly constant and correct. What I now do is:

1. Focus through the viewfinder, using my (oh, so practical) AF confirm adapters
2. Set the right aperture for my shot
3. Press the "SET" button (the one in the middle of the rear wheel) to activate live view.
4. Wait a split second to allow live view metering (which is a bit slow as you can see when you have the live view histogram enabled) and then
5. Press the shutter.

No more problems of overexposed photo's - and much more fun with my few old MF lenses.

The one drawback is that the moment you press the "SET" button the viewfinder blacks out - so you're activating the shutter "in the blind", maybe causing small shifts in composition. But your first shot is also a metering shot - the review will show you what speed goes with the aperture you set, and you can repeat the process in manual mode, or dial in a correct exposure correction value in AV mode.

[fergus]

You could just use manual mode, metering at the aperture you know works well for the lens and then manually recalculate settings for desired taking aperture.

Better and more convenient would be to change your focussing screen to EF-S, making sure to change settings in the camera menu. This should cure your manual focus metering blues and give much better focussing for your faster lenses.

Just posted this in another thread, but think its relevant here too:

[martinsmith99]

Are there a batch of Canon cmeras that cannot meter or something? I have never had an issue with exposure.

[trev]

Me neither, I have NO problem metering on my 20d using m42 lenses and adapter, havnt got around to trying fd lenses yet tho

[vulko]

How about EV correction? Much faster than live view mode, which is good mostly for macro shooting.

[Olivier]

I agree with Fergus.

EF-S matte screen.
M Mode.

[ylyad]

Well, I've the same problem with exposure, with chipped adapter In Av mode. OK wide open, gets worse when stopping down (overexposure).

I don't like LiveView, so I use M mode, and I'm far from being sure my pictures are well exposed. But I prefer to underexpose and post-process than overexpose, results are much better. Maybe I should dig back into the manual and read again on bracketing

I also have a non-chipped adapter, and it works fine in Av mode... But I somehow miss the Af-confirm, even if I admit it's not always 100% perfect - but these are in cases with very small dof, and I'm not sure it's better with full manual focus.

So, not a perfect world

[martinsmith99]

I have found that the 400D gets no brighter when the lens opens wider than F4 and the 40D at F2.8 hence the focus problems. The 5Ds are great for fast lenses!!!!!!

Does your camera expose properly with AF lenses? What metering mode are you using?

[bobcominitaly]

Just to set things straight: I'm not advocating live view, I keep the camera at my eyes al the time. Only thing I do is just before activating the shutter I press the SET button (Live view mode on, of course). Viewfinder gets dark, camera meters in live view mode, I press shutter - bang - no overexposure, regardless of aperture setting. Then I press SET again to get out of live view mode and check my photo (or just shoot another one).

@fergus: I found out that tricking my camera into thinking it has an Ef-S screen reduces the overexposure significantly. Recalculation is a problem: to give you an impression, on an old Nikkor H-C 2.0, an aperture range of:
2 - 2.8 - 4 - 5.6 - 8 - 11 - 16
gives the following exposure range (correctly metered, identical histograms)
640 - 400 - 160 - 80 - 50 - 40 - 20

@martinsmith: where did you get your 40d? (5d's seem to be more reliable, afaik) Glad to swap mine for one that meters flawlessly. Btw: what firmware are you using? Don't know if my 40d was also off before 1.1

@trev: haven't got a 20d to try it, but heard so before. Don't try fd lenses tho - they don't register.

@vulko: see above: I don't shoot in live view mode, just use it for metering. As for EV correction: for some lenses I need more than -2 EV, and the relation between aperture and overexposure isn't linear (see exposure series above)

@Oliver: Ef-s screen is one I'll have to try yet. If it works OK, AV and M are about equivalent (as long as you can trust your metering)

@ylad: problem with underexposing is that it gives you lot ots of noise in the dark areas once you post-process your photo. I've no non-chipped adapters, my eyes aren't suited for screen focusing (In the eighties, I switched from Canon A1 to Nikon F801 just because of AF and focus assist). As for very shallow DOF: autofocus isn't always spot-on, either (which explains about 30% of front- and back-focus complaints, imo)

@martinsmith-2: Would love a brighter viewfinder - but one 5d equals about 20 MF-lenses. No problems with AF-lenses - metering is always OK (unless I goof, of course). The LV trick works on all three metering modes - just as all three metering modes are off when I trust my viewfinder meter info.

[visualopsins]

AFAIK the exposure problem is related to using full-frame lens on crop-sensor camera. Hence no problem on 5D, with its full frame sensor. The larger image circle projected by the full frame lens, the extra light, causes the exposure problem.

Some folks have had success affixing a mask to rear of lens to reduce image circle diameter.

[fergus]

Hi

Just like to stress again that my 40D (crop-sensor camera) has no problems metering exposure in AV and manual mode when using Ef-S focus screen. Unfortunately, I can't get the 400D to do the same.

[bobcominitaly]

Looks as if I'll have to go for that Ef-s screen, then!

[LucisPictor]

[fergus]

Hi

Just to test and confirm that I wasn't kidding myself

Quick test with 40D (Ef-S) and Elmarit-R 60mm on 18% grey background with steady light gave pretty much perfectly consistent results from F/2.8 through to F/22 using AV mode.

400D (cheap split screen, had same problem with standard) same procedure as above. Additionally, I took the F/5.6 exposure setting and shot in manual mode calculating required exposure time, ignoring camera metering. Results below:

F/---AV speed---Exposure----M speed with correct exposure
2.8----1/2500-----1/2 under-----1/2000
4------1/1250-----1/3 under-----1/1000
5.6----1/500-------correct--------1/500
8------1/200-------1/2 over------1/250
11-----1/50--------1 1/3 over----1/125
16-----1/15---------2 over--------1/60
22-----1/8----------2 over--------1/30

When I say correct exposure, I really mean what I think is about right and using this as a comparative baseline.

When I have time I will try this with some different lenses, as I have noticed some variation like my modified Jupiter 9 on the 400D seems to expose fine from F/2 to 5.6 and then follows same trend as above.

[LucisPictor]

I have just ordered a new EE-S screen for my 5D (great price at amazon).
This way, I can use the screen that fits my plans best.
Changing the screen is a breeze.

[martinsmith99]

My experience with EF, EF-S and about 50 MF lenses......

400D with standard screen - No problems metering
40D with all 3 Canon screens and currently fitted with modified Nikon screen - No problems metering
5D with standard and matte screen - No problems metering
5D mkii with standard and matte screen - .....you guessed it, no problems metering

The only camera I no longer have is the 5D. All work fine. Are you guys sure that you're; setting the right screen in the menu, correctly adjusting for backlit/dark/light subjects? Sorry but unless you all have faulty cameras I can't help thinking you must be doing something wrong.

[ylyad]

I've no problem thinking I do something wrong, I'm still a noob in that aspect. However, my tests are simple: take a shot wide-open, close down, take another shot, etc. First one is properly exposed, not the next ones.
When I do the same with non-chipped adapter, everything runs smooth.

What I do is manual, or compensating by locking exposure before closing.

@bobcominitaly: I know post-processing dark zones implies noise, but at least you get something. Burned zones are simply lost.

[martinsmith99]

If you are shooting in manual and not adjusting the shutter speed when you stop the lens down then the exposure will be off. You would need to re-meter after stopping down or slow the shutter speed by the same amount.

[ManualFocus-G]

I have found the adapters to be the problem generally. Many cause the camera to over expose by about a quarter of a stop per aperture stop aftre f2.0. This happens with most of my adapters (bbought in different places) on all Canon cameras I've tried i.e. 300D, 10D, 30D, 40D, 5D.

If I use a lens with a maximum aperture of f3.5, I need to remember to set exposure compensation to -0.5.

I must experiment with exposure settings or different screens. I've currently using average.

Liveview resolves this, but if I stop the lens down once I've activated it, I need to de-activate and then re-activate it or the image is underexposed This behaviour is more like I am used to with the Sony alpha range, which all underexposed the more you stopped down.

[rawhead]

I agree, with 5D, pretty much any manual lens I put on it, always overexposed the more I stopped down. With 5D MkII, it seems to be better, so long as I don't have a filter. Live View tends to consistently give me one stop less exposure than finder. Once I put an ND filter, though, problems about with the finder, so I have to use Live View to get reliable exposure.

I'm using the Eg-s screen.

[ylyad]

[rawhead]

[vulko]

[ylyad]

[fatdeeman]

I have never noticed any MAJOR problems with my 350d but with some lenses I have noticed very slight underexposure the more I stop down but certainly not as bad as several stops