I remember when I got my first 70-200 f/2.8 lens, it was the first version of the Nikkor, and it was a fantastic lens on the 12 Mpx cameras I had back then (D300s and D700). The feel, the look, the balance and about everything was perfect. I still really really like the look of a 70-200 f/2.8 lens on a DSLR, I think it looks simply amazing. Obviously with the increase of megapixels, the older lenses didn’t keep up and needed to be replaced. In the beginning of last year, I got the Tamron SP 70-200mm f/2.8 Di VC USD G2.
To be honest, a 70-200 f/2.8 lens has its limited use because of its focal length, but when it fits, it truly shines. It’s a bit heavy, but well worth it by the quality it produces.
This post should be read together, or preferably after these posts:
Reikan Focal, focus calibration software HERE.
Nikon AF fine tune, how and why HERE.
Tamron Tap-In Console, hardware and software to alter plane of focus among other things HERE.
Tamron 24-70 f/2.8 VC G2, calibrating the lens with Tap-In Console HERE.
A short version of the above articles is something like this. Nikon has had the ability to alter the plane of focus for more than a decade in the menu system in camera. Tamron has had the ability to alter the plane of focus with their Tap-In Console for a couple of years, making changes to the lens directly. The plane of focus is an imaginary line at 90 degrees from the camera where the focus should be at its sharpest, if it’s not you need to compensate with AF fine tune or in-lens compensation. Reikan Focal is a computer software that helps you find the best value to add either in-camera or in-lens. If this doesn’t make sense to you, I advise you to read the full articles linked to above.
When I first got the 70-200 G2, I noticed some photos that were not in completely good focus while others were very good. I know now that it all had to do with aperture and focal lengths used in the different photos, and probably also the focus distances. As mentioned in the 24-70 G2 article, it was totally unexpected that the lens should behave like this, so after consultation with the seller, the lens was returned. The new sample behaved differently but at the same time quite similar to the first copy, as the same was for the 24-70 G2 I also returned.
As we can see from the calibration, the focus is quite all over the place at closest focus distance with massive swing from plus to minus dependent on the aperture. Not terrible bad at 100 mm, but at both ends and 135 mm it is a considerable variation.
Luckily this calms down a bit at medium focus distance, but still I think the variation in both ends are pretty large. In the middle though, it’s fairly stable with little variation only.
And finally, here are the numbers at infinity.
The reason I didn’t do more at smaller apertures, is that the curve in the Focal program is getting increasingly flatter and thereby more and more unreliable at longer focal lengths. The star (*) behind the numbers at 5 meters is that the curve that is so flat that Reikan Focal won’t give a final number, so made my best guess from the curve (should maybe have not written anything like at infinity).
A short explanation of the letters after the values. I’m using Reikan Focal software to help me determine the correct value, and Focal are using four words to tell how good or the quality of the final value is. The best is Excellent, then Good, then Acceptable, and finally Poor. If I get an Acceptable or Poor result, I normally do another run to confirm the first one, and sometimes even a couple of more runs if there is a big difference in the values and in the end calculate the average value.
Another update: I’ve been playing with the Tamron SP 15-30 f/2.8 VC lens last days, and I think I’ve come across a rule of thumb on how to calibrate at infinity, finally. Some may say it’s quite obvious, and I think I’ve been partly fooled by the name “infinity”. In this context it’s not “endless far away”, and when I finally accepted that fact, the pieces started to fall into place more easily. A common thread with all Tamron SP f/2.8 lenses I own, is that the longest reported focus distance correlate somewhat with the focal length. Take the focal length in half and replace millimeters with meters, like 15mm will be 7.5 meters, 70mm will be 35 meters and 200mm will be 100 meters. This is more or less exactly what the longest focus distance reported from the lens and camera, that are embedded onto the image file. In practical terms it means how far away is needed to get to the longest focus distance. It’s just trial and error, as the real measured distance is hardly only a guideline. Take a photo of the focus target and see what is the reported distance in the file and move accordingly if needed. I also think it’s a good idea to not move too far away, only enough and then some. Means if you exactly reach longest focus distance at a certain distance, add a few % so you are sure it is actually enough (I’ve seen reported focus distance move quite a bit between calibration runs without the actual distance have been change). Can confirm that this worked out to be the best solution (so far), get to the closest point from the target that still gives the longest focus distance at that particular focal length (just remember that it will change from focal length to focal length).
Don’t have any before and after photos, but here is one I took today that shows to focus is pretty good. Focus point in the middle of the photo.
The big question is obvious how to calibrate a lens like this when the values are all over the place and we can only add one value for all apertures? That’s up to the owner of the lens obviously, and for me I buy f/2.8 zooms to be used at large apertures. So, I would aim for maybe f/4 at zero with bias towards f/2.8 if the values vary too much. For the future one can hope that Tamron takes the next step and make it possible to calibrate at several apertures too.
This article is a bit shorter than the one about the 24-70 G2, but I feel it would have been too long if it was added into the 24-70 G2 article, so I recommend you to read that one too to get the full picture, and don’t forget that this is about calibrating process and not about the final performance.
Copied from the 24-70 G2 article with some minor adjustments, as I expect not all of you will read that one:
I guess when you’ve read so far you have a feeling the whole story is somewhat negative, and I agree. But remember what this is, a post about calibrating the lens, not about how it performs in daily life. So, I think this slight negative angle is justified, I think Tamron could have provided better user manual on how to do the calibration. In their tech pages online, they could also have explained the behavior of the lens at different lens designs without giving away any design secrets.
As mentioned this is not a post to talk about the performance of the lens, but I will say I really love Tamron lenses and how they make the photos look, so don’t let this post scare you away from any of the fantastic SP lenses from Tamron. I will not hesitate to buy another Tamron lens in the future.
Equipment in use for the calibration:
Reikan FoCal 2 calibration software on my PC.
Reikan focus chart printed in highest quality on 120g non-glossy paper for close and medium distance, printed in A2 size for infinity.
Tamron Tap-In Console and Utility.
Tamron SP 70-200 f/2.8 Di VC USD G2.
Manfrotto 475B tripod.
Kirk BH-3 ball head.
2x Dynaphos soft-boxes with total about 450 watts of low energy lights for illumination of the focus chart indoors and daylight outdoors.
NB, the values mentioned throughout this post is only valid for my lenses together with my camera, do not expect they will fit your lens and camera, they will most likely do it worse! So, do your own calibration and find your own values. I posted those values only to prove the point, not to give the final answer, and that is also why the Tap-In utility is shown empty.
I’ve got a question if you need to calibrate the 70-200 G2, and as with most other things in life there isn’t any straight answer to that either. I expect that there are sample variations for the 70-200 as with all other lenses, so some may be quite good, other consequently back or front focuses, while other is a more mixed bag. I will recommend you to test your lens and see for your self. If the lens only back or front focuses, you may solve it with in-camera adjustment, but if the lens has both front and back focus, you should definitely consider the Tap-In console and do a proper calibration.
If you have some comments or questions, so, come on, let me hear from you in the comments below!
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