Tamron 24-70 G2 front focus at f/2.8, back focus at f/5.6 (70mm)

Started Feb 22, 2018 | Discussions
RccIT New Member • Posts: 3
Tamron 24-70 G2 front focus at f/2.8, back focus at f/5.6 (70mm)

Hello everyone,

I need your advice:

I tried two different copies of this lens and they both require extremely different AF fine tuning at different F values for the same focal length and the same distance.

How do I fix that? I'm using the tap-in console but there is no option. I'm not going to order a third lens, since I'm not impressed at all.

Do you have any idea?

Thanks!

Tamron SP 24-70mm F2.8 G2
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Luftwalk Regular Member • Posts: 193
Re: Tamron 24-70 G2 front focus at f/2.8, back focus at f/5.6 (70mm)

Hi,

I know this is probably a long shot, but are you refocusing when changing apertures? So you focus at f2.8, change to f5.6 and then refocus again? If you're not you can be seeing the effects of focus shift.

 Luftwalk's gear list:Luftwalk's gear list
Nikon Z6 Nikon AF-S Nikkor 70-200mm f/2.8G ED VR II Nikon AF-S Nikkor 50mm f/1.8G Sigma 24-35mm F2 DG HSM Art Nikon 200-500mm F5.6E ED VR +3 more
OP RccIT New Member • Posts: 3
Re: Tamron 24-70 G2 front focus at f/2.8, back focus at f/5.6 (70mm)

Luftwalk wrote:

Hi,

I know this is probably a long shot, but are you refocusing when changing apertures? So you focus at f2.8, change to f5.6 and then refocus again? If you're not you can be seeing the effects of focus shift.

Yes, I do refocus after changing the aperture.

This lens shows quite a bit of focus shift, but it is not a problem for me! I only need the focus calibration to work at different apertures!!

Warkari Contributing Member • Posts: 723
Re: Tamron 24-70 G2 front focus at f/2.8, back focus at f/5.6 (70mm)
1

RccIT wrote:

Luftwalk wrote:

Hi,

I know this is probably a long shot, but are you refocusing when changing apertures? So you focus at f2.8, change to f5.6 and then refocus again? If you're not you can be seeing the effects of focus shift.

Yes, I do refocus after changing the aperture.

This lens shows quite a bit of focus shift, but it is not a problem for me! I only need the focus calibration to work at different apertures!!

If you are re-acquiring focus at f5.6, then what you are seeing is focus shift.

I don't think you can calibrate out the focus shift, especially with third party lenses. Some folks think OEM cameras have focus shift compensation for their own lenses.

If it is an option, you can shoot such scenes in live view mode to avoid this issue.

Amit

 Warkari's gear list:Warkari's gear list
Nikon D750 Nikon D500 Sigma 50-150mm F2.8 EX DC APO OS HSM Nikon 85mm F1.8G Tamron SP 24-70mm F2.8 Di VC USD +6 more
David5833 Senior Member • Posts: 1,233
Re: Tamron 24-70 G2 front focus at f/2.8, back focus at f/5.6 (70mm)

RccIT wrote:

Hello everyone,

I need your advice:

I tried two different copies of this lens and they both require extremely different AF fine tuning at different F values for the same focal length and the same distance.

How do I fix that? I'm using the tap-in console but there is no option. I'm not going to order a third lens, since I'm not impressed at all.

Do you have any idea?

Thanks!

Like you, I returned the first copy to the seller for exchange; the tap-in console was maxxed out at a few settings.  The second copy was better but still not acceptable.  Rather than try a third copy, I sent it to Tamron USA for adjustment.  It took three trips for adjustment before they finally got it right.  On the third trip it was escalated to the senior technician after the first-level tech found no problem.  They finally figured it out but didn't disclose to me what the problem was or how they fixed it.

If you are in the USA and it is in warranty, my advice is to be persistent with Tamron until they either fix it or give you a new one.  Be sure to include a detailed description of the issues when you send it in.  Not sure how you would fare if outside the USA.

 David5833's gear list:David5833's gear list
Nikon D810 Olympus OM-D E-M10 II Nikon D7500 Nikon AF Micro-Nikkor 200mm f/4D ED-IF Sigma 15mm F2.8 EX DG Diagonal Fisheye +10 more
calin Forum Member • Posts: 85
Re: Tamron 24-70 G2 front focus at f/2.8, back focus at f/5.6 (70mm)

David5833 wrote:

RccIT wrote:

Hello everyone,

I need your advice:

I tried two different copies of this lens and they both require extremely different AF fine tuning at different F values for the same focal length and the same distance.

How do I fix that? I'm using the tap-in console but there is no option. I'm not going to order a third lens, since I'm not impressed at all.

Do you have any idea?

Thanks!

Like you, I returned the first copy to the seller for exchange; the tap-in console was maxxed out at a few settings. The second copy was better but still not acceptable. Rather than try a third copy, I sent it to Tamron USA for adjustment. It took three trips for adjustment before they finally got it right. On the third trip it was escalated to the senior technician after the first-level tech found no problem. They finally figured it out but didn't disclose to me what the problem was or how they fixed it.

If you are in the USA and it is in warranty, my advice is to be persistent with Tamron until they either fix it or give you a new one. Be sure to include a detailed description of the issues when you send it in. Not sure how you would fare if outside the USA.

Canon and Nikon focus through the lens at max aperture, in this case 2.8. If you shoot at 5.6 the focus happens at 2.8 then before taking the picture the aperture is changed to 5.6.

At 70mm and close to subject focusing this lens (and the canon 24-70) are known to have spherical aberration which result in the described behavior.

see: https://www.lenstip.com/340.5-Lens_review-Tamron_SP_24-70_mm_f_2.8_Di_VC_USD_Chromatic_and_spherical_aberration.html that is similar to G2

To reduce the impact of the spherical aberration I modify the tap-in console calibration at 70mm 1.25ft/3 ft to value between the required cal at 2.8 and the required value at 5.6 but with more preference for 5.6.   I do not use 2.8 up-close at 70mm.

 calin's gear list:calin's gear list
Canon EOS 70D Canon EOS 5D Mark IV Canon EF 50mm F1.8 II Canon EF-S 17-55mm f/2.8 IS USM Canon EF-S 60mm f/2.8 Macro USM +2 more
Cameranoobie Senior Member • Posts: 2,747
Re: Tamron 24-70 G2 front focus at f/2.8, back focus at f/5.6 (70mm)

RccIT wrote:

Hello everyone,

I need your advice:

I tried two different copies of this lens and they both require extremely different AF fine tuning at different F values for the same focal length and the same distance.

How do I fix that? I'm using the tap-in console but there is no option. I'm not going to order a third lens, since I'm not impressed at all.

Do you have any idea?

Thanks!

Sounds like you have a defective copy. My very first copy of my G2 70-200 had this exact issue. It had front and back focusing so severe that even after putting the adjustment to the max setting in the Tamron app with the dock, it still didn't fix it so I swapped it for another copy.

 Cameranoobie's gear list:Cameranoobie's gear list
Sony RX10 IV Nikon D5500 Nikon D5600 Nikon AF-S DX Nikkor 35mm F1.8G Tokina AT-X Pro 11-16mm f/2.8 DX +14 more
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