EF-M Adpter: Focus problems

Hello!

Most of the time, I use my M5 and M50 with adapted, rather cheap EF lenses. I own a Viltrox EF-M adpater as well as its Canon counterpart.

Wondering why many pictures lack a bit of sharpness, I did a couple of test and I was quite surprised that using the manual focus produced considerably sharper pictures than shooting with auto focus. The effect is the same for both adapters and both cameras. It's most obvious with more open apertures - and when digitizing 35mm negatives with my 50mm Sigma f/2.8 1:1 Macro, most likely due to the shallow depth of field.

To illustrate the problem: First, I set the AF-switch on the lens to MF, focus as precise as possible and take a photo, all using a tripod. The resulting picture is perfectly sharp (or as sharp as the more or less open aperture allows). Then, when switching back to AF and half-pressing the shutter button, I can see a small but clearly visible rotation of the focus ring. The photo taken afterwards is not as sharp as the one taken with manual focus.

With the 15-45mm EF-M kit lens, there is no difference between AF and MF pictures, despite some MF ones being less sharp due to unprecise manual focusing.

I'm pretty confused and quite a bit depressed, since I sold my A6300 and my A7 Mk I last summer because I was unhappy with the reliability and speed of the LA-EA 3 and LA-EA 4. I had some experience with an EOS M6 and adapted EF lenses and I had the impression that the AF worked very fast and (so I thought) reliable with the adapter, too. At least better than the adapters on my Sony cameras.

Does anybody have any idea what's causing the weird focus problems?

Thanks!

I think you'll need to post your AF settings, and it'll also be good to post the lens(es) you are using.

I never had any front-focusing or back-focusing issues with my M5 and any lenses (as you describe).

R2

R2D2 wrote:

I think you'll need to post your AF settings, and it'll also be good to post the lens(es) you are using.

I never had any front-focusing or back-focusing issues with my M5 and any lenses (as you describe).

R2

Hi!

Thanks for your reply! I mostly use a Tamron 18-200mm F3.5-6.3 Di II VC, a Sigma 18-135 F3.8-5.6 Macro and a Sigma 50mm F2.8 Macro. The tests were made with One-Shot, One-Point AF. The AF point was centered, the AF frame size some times small, some times normal.

The results were mostly identical with all three lenses.

What I totally don't understand: How can a mirrorless camera with AF evaluation on sensor produce any effect resembling old time back- / front focus problems? I wondered whether there might be some communications problem between camera, adapter and lens?

And now that I think about it: Many of my not-so-sharp (sometimes _really_ soft) pictures were shot with the Tamron when doing landscapes with focus objects well behind the infinity position. But sometimes I noticed that the focus ring was not in infinity position but instead a bit before.

Robert Seetzen wrote:

R2D2 wrote:

I think you'll need to post your AF settings, and it'll also be good to post the lens(es) you are using.

I never had any front-focusing or back-focusing issues with my M5 and any lenses (as you describe).

R2

Hi!

Thanks for your reply! I mostly use a Tamron 18-200mm F3.5-6.3 Di II VC, a Sigma 18-135 F3.8-5.6 Macro and a Sigma 50mm F2.8 Macro. The tests were made with One-Shot, One-Point AF. The AF point was centered, the AF frame size some times small, some times normal.

Thanks for the info (your AF settings are fine).  My first thought is that the issue lies with your lenses.  Check with the (3rd party) manuf to see if any of them need firmware updates.  Canon will of course tell you to use Canon lenses.  

The results were mostly identical with all three lenses.

I have a couple of Sigma EF-M lenses which work wonderfully.    Highly recommended.

What I totally don't understand: How can a mirrorless camera with AF evaluation on sensor produce any effect resembling old time back- / front focus problems? I wondered whether there might be some communications problem between camera, adapter and lens?

Good guess.  Poor AF performance is the first place that incompatibility issues show up.

And now that I think about it: Many of my not-so-sharp (sometimes _really_ soft) pictures were shot with the Tamron when doing landscapes with focus objects well behind the infinity position. But sometimes I noticed that the focus ring was not in infinity position but instead a bit before.

Definitely check with Tamron to see if it needs an update, or if it’s even compatible at all (esp if it’s not the EF-M version).  Unfortunately most of the incompatibility issues I’ve read about on this forum are regarding Tamron lenses.

Best of luck to you!

R2

I have the Tamron 18-400. My first copy front-focussed very badly. My second copy is perfect.

It could be your lenses. I've never heard of the adapter itself causing issues.

There's no electronics in the device - it's just some connection extensions. Maybe one of the connectors needs a clean?

TrackDayLT4 wrote:

On my M5 in one shot mode, I have a couple of adapted lenses that front focus.

I believe this has to do with how the dual pixel autofocus calculates a focus distance and tells the lens to move. In one shot mode with adapted lenses, it dos not appear to confirm focus. This problem goes away using Servo instead of One Shot.

Try repeating your test with Servo and see if the focus improves.

Cheers

Thanks for your tip! It's Monday and quite a lot to do, so I had very little time to do a few comparisons between One-Shot and Servo. At first glance, I'd say that there is little difference, though I didn't check with 'scanning' negatives, where the problems were most obvious.

I'll tell more as soon as I have the time to do some more meaningful tests.

R2D2 wrote:

Robert Seetzen wrote:

(...) I mostly use a Tamron 18-200mm F3.5-6.3 Di II VC, a Sigma 18-135 F3.8-5.6 Macro and a Sigma 50mm F2.8 Macro. The tests were made with One-Shot, One-Point AF. The AF point was centered, the AF frame size some times small, some times normal.

Thanks for the info (your AF settings are fine). My first thought is that the issue lies with your lenses. Check with the (3rd party) manuf to see if any of them need firmware updates. Canon will of course tell you to use Canon lenses.

Yes, I'm frightened I just fetched the 'wrong' lenses. At least in combination with an M series camera.

The results were mostly identical with all three lenses.

I have a couple of Sigma EF-M lenses which work wonderfully. Highly recommended.

There won't be enough money in my pocket for new (as in fresh from the factory) lenses.  That's why the adapter is so important for me. And there are many excellent, not-to-expensive second hand EF lenses out there.

What I totally don't understand: How can a mirrorless camera with AF evaluation on sensor produce any effect resembling old time back- / front focus problems? I wondered whether there might be some communications problem between camera, adapter and lens?

Good guess. Poor AF performance is the first place that incompatibility issues show up.

It seems so, yes

And now that I think about it: Many of my not-so-sharp (sometimes _really_ soft) pictures were shot with the Tamron when doing landscapes with focus objects well behind the infinity position. But sometimes I noticed that the focus ring was not in infinity position but instead a bit before.

Definitely check with Tamron to see if it needs an update, or if it’s even compatible at all (esp if it’s not the EF-M version). Unfortunately most of the incompatibility issues I’ve read about on this forum are regarding Tamron lenses.

Tried today to get through on their hotline here in Germany, perhaps more luck tomorrow...

Best of luck to you!

R2

Thanks a lot for thoughts and your tips!

ken_in_nh wrote:

Hard to imagine any way front or back focus can happen with mirrorless, especially since the problem in DSLRs is a mechanical one.

My experience with a m6ii is that landscapes always present focus problems since the photo is cluttered and even the spot on mirrorless is huge compared to my former 70D which had a much smaller spot focus point.

But if I understand correctly, these are focus problems that are more likely related to an incorrect focus point selection by the camera, right? Or have you also noticed this in situations where the AF point was on an unambiguous part of the image?

ken_in_nh wrote:

Robert Seetzen wrote:

ken_in_nh wrote:

Hard to imagine any way front or back focus can happen with mirrorless, especially since the problem in DSLRs is a mechanical one.

My experience with a m6ii is that landscapes always present focus problems since the photo is cluttered and even the spot on mirrorless is huge compared to my former 70D which had a much smaller spot focus point.

But if I understand correctly, these are focus problems that are more likely related to an incorrect focus point selection by the camera, right? Or have you also noticed this in situations where the AF point was on an unambiguous part of the image?

I've only noticed something in cluttered scenes.

I tend to use touch screen focus most of the time. You may want to try that?

I mostly shoot using the viewfinder and I use Touch&Drag AF if needed (see below).

Also, Canon's Digital Photo Professional will show focus points. You should check with the software. It should also tell you if focus did not lock.

A few days ago, I installed DPP for this purpose and I found that I did in fact set nonsense focus points from time to time - probably unintentionally with my nose since I had "Touch & Drag AF" active on the whole panel. Now I switched that to "Bottom right corner", which works fine and avoids setting random focus points

Anyway, in most of the too-soft pictures, the AF point was placed as intended. But the results are still puzzling, not at least because most of those pictures weren't shot to check some AF problems. I guess I will have to do some more structured testing to narrow down the source of the error.

ken_in_nh wrote:

Robert Seetzen wrote:

A few days ago, I installed DPP for this purpose and I found that I did in fact set nonsense focus points from time to time - probably unintentionally with my nose since I had "Touch & Drag AF" active on the whole panel. Now I switched that to "Bottom right corner", which works fine and avoids setting random focus points

I've had the same problem - nose focus points, to the degree that I stopped using the EVF. My life has been much happier since then.

Problem is, I'm 57 and to use the display for shooting becomes more and more difficult without reading glasses - and I don't like varifocals. But since I switched the Touch&Drag settings to "Bottom right" area and "Absolute" positioning, setting the AF point works pretty reliable. Regardless of that, it would of course be nice if the viewfinders on the M5 and M50 could handle large contrast scenes better than they do.

istscott wrote:

I don't have any answers, but I did buy a new Canon 85mm f/1.8 stm that had inconsistent focus accuracy with the official adapter. Though the 50mm f/1.8 stm I have works well.

Oh, that doesn't sound good. Up until now I was hoping that these problems would be limited to lenses from other manufacturers - simply because Sigma, Tamron, etc. do not have access to the full communication protocols between the camera and lens.

Perhaps you have the opportunity to try out your 85mm on an SLR? Because if there weren't any focus problems there, it would definitely be due to problems with the adapter.

Do you use the lenses on an M-Series or with R camera?

Robert Seetzen wrote:

istscott wrote:

I don't have any answers, but I did buy a new Canon 85mm f/1.8 stm that had inconsistent focus accuracy with the official adapter. Though the 50mm f/1.8 stm I have works well.

Oh, that doesn't sound good. Up until now I was hoping that these problems would be limited to lenses from other manufacturers - simply because Sigma, Tamron, etc. do not have access to the full communication protocols between the camera and lens.

Perhaps you have the opportunity to try out your 85mm on an SLR? Because if there weren't any focus problems there, it would definitely be due to problems with the adapter.

Do you use the lenses on an M-Series or with R camera?

I’d avoid conflating issues here.  You’ll muddy the waters and then never find your way out.

For now stick to determining why your Tamron lenses are misbehaving.    Have they offered any solutions yet?

The Canon EF 85mm f/1.8 USM (there is no EF 85mm STM) can be a little squirrely on any body.  Mine needed tons of AFMA on my DSLRs, and it is under-performing on my mirrorless cameras.  I’m ditching it in favor of the 85mm f/1.4L soonest I can.

I’d reiterate that I don’t think your issue lies with the adapter (and the body is proven).  Take it from there...

Best of luck!

R2