I love the optics but find AF very inconsistent on the 6D

Started Nov 5, 2019 | User reviews
47872Mike Regular Member • Posts: 210
I love the optics but find AF very inconsistent on the 6D

Not much more to add, really. I have used each incarnation of Canon 50/1.8. The optics are great on full frame and fairly good on 1.6 crop.
The first version had a loud AF motor but mine worked well.
The second version was made like a toy and mine had equally great optics, but the mechanical build was so sloppy that AF was not reliable due to play in the mechanism. 
I thought the STM version would solve AF, but it doesn't on my 6D. In good light it works accurately. In low light where I am often wanting to use this lens, it will focus inconsistently. If I take three shots, they will all be focused on a different spot. if I'm lucky, one will be focused where I pointed the AF sensor. You can tell whether or not it is going to focus correctly because when it's playing up, you can hear it re-focusing when you haven't moved the camera and the subject hasn't moved.
I tried it on an old 10D and it seemed a bit less prone to inconsistent AF.
As our American friends say, "Go figure"....

The build is better than the second toy version but still not as good as the 40/2.8. I don't understand why it cannot focus consistently in low light, but it's making me want to try another Mk1.  
General note on the optics (full frame):

Good contrast in the image centre right from f1.8. Gradual improvement to a peak at about f8, but for most practical purposes, very good from 2.8 and outstanding by f4. Resolution is great. 
This version has extra aperture blades (no pentagonal bokeh when stopped down, like you get on the other two versions) and focuses slightly closer.

 47872Mike's gear list:47872Mike's gear list
Canon EOS 10D Canon EOS 20D Canon EOS 50D Sony SLT-A37 Canon EOS 6D +13 more
Canon EF 50mm F1.8 STM
Prime lens • Canon EF • 0570C002
Announced: May 11, 2015
47872Mike's score
3.0
Average community score
3.6
Canon EF 50mm F1.8 STM Canon EOS 10D Canon EOS 6D
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ZX11
ZX11 Veteran Member • Posts: 5,455
Use live view

47872Mike wrote:

Not much more to add, really. I have used each incarnation of Canon 50/1.8. The optics are great on full frame and fairly good on 1.6 crop.
The first version had a loud AF motor but mine worked well.
The second version was made like a toy and mine had equally great optics, but the mechanical build was so sloppy that AF was not reliable due to play in the mechanism.
I thought the STM version would solve AF, but it doesn't on my 6D. In good light it works accurately. In low light where I am often wanting to use this lens, it will focus inconsistently. If I take three shots, they will all be focused on a different spot. if I'm lucky, one will be focused where I pointed the AF sensor. You can tell whether or not it is going to focus correctly because when it's playing up, you can hear it re-focusing when you haven't moved the camera and the subject hasn't moved.
I tried it on an old 10D and it seemed a bit less prone to inconsistent AF.
As our American friends say, "Go figure"....

The build is better than the second toy version but still not as good as the 40/2.8. I don't understand why it cannot focus consistently in low light, but it's making me want to try another Mk1.
General note on the optics (full frame):

Good contrast in the image centre right from f1.8. Gradual improvement to a peak at about f8, but for most practical purposes, very good from 2.8 and outstanding by f4. Resolution is great.
This version has extra aperture blades (no pentagonal bokeh when stopped down, like you get on the other two versions) and focuses slightly closer.

It will focus accurately in live view.

I think the OVF focus system is tricked by lenses that don't handle purple fringing well (and light outside visual wavelengths) and have poor low light contrast.  In low light the OVF sees no sharp focus position and then settles for close enough.  Live view will lock right on a high percentage of the time.

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 ZX11's gear list:ZX11's gear list
Canon EF 50mm F1.4 USM Canon EF 85mm F1.8 USM Canon 70-200 F2.8L III Canon RF 35mm F1.8 IS STM Macro Canon RF 24-105mm F4L IS USM +1 more
OP 47872Mike Regular Member • Posts: 210
Re: Use live view

ZX11 wrote:

47872Mike wrote:

Not much more to add, really. I have used each incarnation of Canon 50/1.8. The optics are great on full frame and fairly good on 1.6 crop.
The first version had a loud AF motor but mine worked well.
The second version was made like a toy and mine had equally great optics, but the mechanical build was so sloppy that AF was not reliable due to play in the mechanism.
I thought the STM version would solve AF, but it doesn't on my 6D. In good light it works accurately. In low light where I am often wanting to use this lens, it will focus inconsistently. If I take three shots, they will all be focused on a different spot. if I'm lucky, one will be focused where I pointed the AF sensor. You can tell whether or not it is going to focus correctly because when it's playing up, you can hear it re-focusing when you haven't moved the camera and the subject hasn't moved.
I tried it on an old 10D and it seemed a bit less prone to inconsistent AF.
As our American friends say, "Go figure"....

The build is better than the second toy version but still not as good as the 40/2.8. I don't understand why it cannot focus consistently in low light, but it's making me want to try another Mk1.
General note on the optics (full frame):

Good contrast in the image centre right from f1.8. Gradual improvement to a peak at about f8, but for most practical purposes, very good from 2.8 and outstanding by f4. Resolution is great.
This version has extra aperture blades (no pentagonal bokeh when stopped down, like you get on the other two versions) and focuses slightly closer.

It will focus accurately in live view.

I think the OVF focus system is tricked by lenses that don't handle purple fringing well (and light outside visual wavelengths) and have poor low light contrast. In low light the OVF sees no sharp focus position and then settles for close enough. Live view will lock right on a high percentage of the time.

Yes, the camera can focus it accurately in live view. I have my suspicions that it's not an optical problem but an electro-mechanical one, but I'll know if I get another Mk1 to test!

 47872Mike's gear list:47872Mike's gear list
Canon EOS 10D Canon EOS 20D Canon EOS 50D Sony SLT-A37 Canon EOS 6D +13 more
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