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Yet Another Tamron 150-600 Thread! Interesting Observati...
  
 
pKai
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p.1 #1 · p.1 #1 · Yet Another Tamron 150-600 Thread! Interesting Observations --


I finally got my Tamron 150-600 last week -- Thanks Art at Palm Beach Photographic Center --

I spent a couple of days running it through FoCal and shooting various boring objects for familiarization purposes and came up with the following information.

Regardig FoCal -- all testing was done at 600mm

On my 5D2 the microfocus setting came out to a +8. Odd for this body since all my other lenses are within a couple of points of ZERO plus or minus..... I think "maybe the lens is off" -- but then....

.... on my 7D, the MF adustment came out at +2, which is well within reason.... Interesting, I thought.....

I then ran the optimal F-stop test. On both bodies the best F-Stop came out to be F14 with F11 being a close 2nd and F8, a close 3rd. Diffraction-wise, the 7D began falling apart at F16 with the 5D2 holding one more stop to F22. So far, no surprises.....

As an engineer by training, I love and trust data, but as an artist by aspiration/inspiration, I like to subjectively look at stuff as well. Here, things got interesting







This is the 7D comparing the optimal F14 on the left and the sucky F6.3 on the right -- no surprises...







This is the 5D2 with optimal F14 on the left and the supposedly sucky F6.3 on the right -- notice the almost lack of difference?







Here is the 5D2 at 100% to compare apples/apples with the 7d.




Feb 17, 2014 at 06:01 PM
pKai
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p.1 #2 · p.1 #2 · Yet Another Tamron 150-600 Thread! Interesting Observations --


I ran this test several times because I could not believe my eyes every time I got the same results..... I see little difference from 6.3 to 14 on the 5D where on the 7D there is a HUGE difference. Also, yes, I eye-ball checked the +8 microadjustment and it seems right for the 5D2.

Add this info to the DxO results which point in the same direction (they rated the lens higher with the FF 5d3 than the 7D) and what? Is this lens a full-frame lens? Wow! Is anyone else noticing better IQ and/or better IQ at wider F-stops with full-frame bodies versus crop?

My 1D4 is at Canon for some TLC -- when it comes back I will redo these tests to see........

All that said, I am fairly happy with this lens for its primary intended purpose in my world.... semi-static wildlife with full-frame.

Thoughs?




  Canon EOS 5D Mark II    TAMRON SP 150-600mm F/5-6.3 Di VC USD A011 lens    600mm    f/14.0    1/800s    1600 ISO    -0.7 EV  






  Canon EOS 5D Mark II    TAMRON SP 150-600mm F/5-6.3 Di VC USD A011 lens    600mm    f/14.0    1/640s    1600 ISO    -0.7 EV  



Edited on Feb 17, 2014 at 06:13 PM · View previous versions



Feb 17, 2014 at 06:06 PM
alundeb
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p.1 #3 · p.1 #3 · Yet Another Tamron 150-600 Thread! Interesting Observations --


So you found inconsistent AF?

Ephotozine rates it to give highest MTF50 at f/8 in center.

I will never buy a lens with optimal sharpness at f/14, in center.




Edited on Feb 17, 2014 at 06:20 PM · View previous versions



Feb 17, 2014 at 06:12 PM
pKai
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p.1 #4 · p.1 #4 · Yet Another Tamron 150-600 Thread! Interesting Observations --


alundeb wrote:
So you found inconsistent AF?

I will never buy a lens with optimal sharpness at f/14, in center.


No... its consistent --- I shot over 1,000 frames in the field (IOW, not counting the FoCal stuff) and focus was pretty consistent... Issues covered elsewhere with fast-moving subjects and some bodies notwithstanding -- with the semi-static subjects I shot and my 5D2, the lens focuses remarkably well. Out of the 1,000 odd images I shot yesterday, most were technically in focus.

What I did observe was a much larger difference between F6.3 and F14 on the 7D than on the 5D2..... which I did not expect.... and this difference was consistent as well. For some reason this lens performs much better at wide apertures on FF than it does on crop bodies.... That is something I have NOT observed on any other lens I own.... and something I would notrefer to as "inconsistent focus".....

As for F11/14 testing out to be the optimal apertures, that's no shock to me from a $1,100 lens with this zoom range. If we want sharp at F4 corner to corner, we need to add a zero to the price tag.


Edited on Feb 17, 2014 at 06:23 PM · View previous versions



Feb 17, 2014 at 06:19 PM
alundeb
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p.1 #5 · p.1 #5 · Yet Another Tamron 150-600 Thread! Interesting Observations --


Maybe consistently different focus then?

Ephotozine rates it to give highest MTF50 at f/8 in center.




Feb 17, 2014 at 06:21 PM
alundeb
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p.1 #6 · p.1 #6 · Yet Another Tamron 150-600 Thread! Interesting Observations --


I think what you found coincides well with all those soft looking initial test images we used to see. Theos looked "f/16 soft".



Feb 17, 2014 at 06:25 PM
pKai
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p.1 #7 · p.1 #7 · Yet Another Tamron 150-600 Thread! Interesting Observations --


Could be.... what I don't get is why the huge difference between crop and FF at wider apertures.


Feb 18, 2014 at 03:05 AM
cameron12x
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p.1 #8 · p.1 #8 · Yet Another Tamron 150-600 Thread! Interesting Observations --


pKai wrote:
Could be.... what I don't get is why the huge difference between crop and FF at wider apertures.


Me either. I've heard of lenses optimized for crop cameras, but I'm not familiar with ones optimized for full-frame sensors.

Riddle me this. I admit that I don't understand.

If a given lens performance is optimized across the entire image circle produced by the lens then why is it that a crop body (which crops the central part of that image circle) is not also optimized by default?



Feb 18, 2014 at 03:15 AM
pKai
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p.1 #9 · p.1 #9 · Yet Another Tamron 150-600 Thread! Interesting Observations --


Whatever is going on here, I don't think it was done on purpose.... It could be something as simple as my copy of the lens, which is why I posted here.....

As you point out, it makes no sense that a camera that uses less of the image circle would exhibit worse performance... if anything, the opposite is often true.

Back in the early days of digital there was heated discussion about the angle at which light rays strike the photo sites on the sensor and how that was different from film and how sensors with bigger photo sites were more forgiving of lenses that had steeper angles than sensors with smaller ones. I wonder if something like this could be going on here. To me, this was (and is) squarely in the realm of pixel-peeping and measurebating, both habits which I (usually) want nothing to do with... This, however, is a curiosity hard to resist even for someone for whom the phrase "its all about the print on the wall" is usually gospel.



Feb 18, 2014 at 03:23 AM
jcolwell
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p.1 #10 · p.1 #10 · Yet Another Tamron 150-600 Thread! Interesting Observations --


cameron12x wrote:
Me either. I've heard of lenses optimized for crop cameras, but I'm not familiar with ones optimized for full-frame sensors.

Riddle me this. I admit that I don't understand.

If a given lens performance is optimized across the entire image circle produced by the lens then why is it that a crop body (which crops the central part of that image circle) is not also optimized by default?


It's probably related to resolution. Given that most contemporay APS-C sensors have higher pixel density than FF sensors (and so, they have higher resolution), it's quite possible that you (or Canikon) could make an APS-C lens that has higher resolution in the APS-C sized image circle, than it could for a FF image circle. The key parameters being the variation accuracy of lens element geometry as a function of lens element size (i.e. it's easier to make accurate optics when they're smaller - much like making sensors).

P.S. you can optimize lens performance across a smaller image circle more easily than across a larger image circle.



Feb 18, 2014 at 03:26 AM
 

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cameron12x
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p.1 #11 · p.1 #11 · Yet Another Tamron 150-600 Thread! Interesting Observations --


jcolwell wrote:
It's probably related to resolution. Given that most contemporay APS-C sensors have higher pixel density than FF sensors (and so, they have higher resolution), it's quite possible that you (or Canikon) could make an APS-C lens that has higher resolution in the APS-C sized image circle, than it could for a FF image circle. The key parameters being the variation accuracy of lens element geometry as a function of lens element size (i.e. it's easier to make accurate optics when they're smaller - much like making sensors).

P.S. you can optimize lens performance across a smaller image circle more easily than
...Show more

If it's easier to optimize lens performance across a smaller image circle then it's interesting why Tamron chose instead to optimize for a larger image circle? I'm not sure I get that.

Can't we just use the usual metric of lp/mm as a normalized resolution metric for both crop and full-frame sensors?

In other words, the lp/mm resolution of the lens is good enough for a less dense full-frame sensor, but doesn't cut mustard for a more dense crop sensor?



Feb 18, 2014 at 03:36 AM
Shutterbug2006
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p.1 #12 · p.1 #12 · Yet Another Tamron 150-600 Thread! Interesting Observations --


If it's any consolation, all the shots in the first post are sucky ...


Feb 18, 2014 at 06:13 AM
fraga
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p.1 #13 · p.1 #13 · Yet Another Tamron 150-600 Thread! Interesting Observations --


I agree with Jim, I think it's pixel-density related.
In the center of the frame, a high MP crop sensor will put more stress on the lens than a FF sensor with a lower pixel-density.



Feb 18, 2014 at 10:50 AM
alundeb
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p.1 #14 · p.1 #14 · Yet Another Tamron 150-600 Thread! Interesting Observations --


But the problem is that with the low pixel density camera, the "optimal" aperture is as bad as wide open. That is at odds with everything.


Edited on Feb 18, 2014 at 11:11 AM · View previous versions



Feb 18, 2014 at 11:07 AM
Pixel Perfect
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p.1 #15 · p.1 #15 · Yet Another Tamron 150-600 Thread! Interesting Observations --


To me the answer is simple. The 7D focus is off and at f/6.3 the test target was not in in perfect focus, but at f/14 DoF was enough to overcome the the misfocus, even though the 7D is diffraction affected at f/14, it's still vastly better than being oof. The 5D2 nailed the focus and stopping down has little effect.

I think your MA of +2 was not correct for your 7D.



Feb 18, 2014 at 11:10 AM
alundeb
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p.1 #16 · p.1 #16 · Yet Another Tamron 150-600 Thread! Interesting Observations --


The optimal aperture of a lens is the same for all pixel densities, and with this lens it is noticeable sharper with a FF Canon body at f/8 than f/6.3 both a ephotozine, lensrentals and dxomark.



Feb 18, 2014 at 11:13 AM
Pixel Perfect
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p.1 #17 · p.1 #17 · Yet Another Tamron 150-600 Thread! Interesting Observations --


fraga wrote:
I agree with Jim, I think it's pixel-density related.
In the center of the frame, a high MP crop sensor will put more stress on the lens than a FF sensor with a lower pixel-density.


The total blur of the system is given by the root mean square sums of the individual blurs due to the lens and sensor.

blur_total = sqrt(blur_lens^2 + blur_sensor^2)

In this case the blurs are just the reciprocal of the resolution of each component. For a 7D with 4.3um (=4.3*10^-3 mm) pixels the sensor has a maximum resolution of ~ 1/(2*4.3*10^-3) = 116lp/mm. The factor 2 is for Nyquist. A 5D 2 with 6.4um pixels has a maximum resolution of 1/(2*6.4x10^-3) = 78lp/mm. Let's say we have a perfect lens, with a an MTF50 resolution at f/8 of 80lp/mm (a representative value) and a figure which is independent of camera.

blur_total_7D = sqrt(1/116^2 + 1/80^2) = 1/66, thus resolution is 66lp/mm
blur_total-5D = sqrt(1/78^2 + 1/80^2) = 1/56, thus resolution is 56lp/mm

In no case are you worse off with a higher resolution sensor even if lens resolutions doesn't improve.


Edited on Feb 18, 2014 at 11:59 AM · View previous versions



Feb 18, 2014 at 11:38 AM
cameron12x
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p.1 #18 · p.1 #18 · Yet Another Tamron 150-600 Thread! Interesting Observations --


Thank you, Pixel Perfect, for a great analysis and also for using lp/mm as a metric!

For the 5D2, however, shouldn't the resolution instead be: 1/(2*6.4x10^-3) -- you used 6.7 instead of 6.4?

Could we also use an analogy of "over-sampling" when comparing a more dense sensor to a less dense one? I'm just throwing that out there, as I don't know.

On the flip-side, what if the lens in question only is capable of ~60 lp/mm resolution? In this use case that would work fine for the 5D2 sensor, but wouldn't reach the maximum resolution of the 7D.

Thus, when pixel-peeping or analyzing the lens performance on the crop sensor, the DXO performance metric would be lower than that reported for the full-frame sensor?



Edited on Feb 18, 2014 at 12:07 PM · View previous versions



Feb 18, 2014 at 11:53 AM
Pixel Perfect
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p.1 #19 · p.1 #19 · Yet Another Tamron 150-600 Thread! Interesting Observations --


cameron12x wrote:
Thank you, Pixel Perfect, for a great analysis and also for using lp/mm as a metric!

For the 5D2, however, shouldn't the resolution instead be: 1/(2*6.4x10^-3) -- you used 6.7 instead of 6.4?


Thanks, yes the I got the right answer but forgot to change the pixel size. I was initially working with 6.7um pixels not 6.4um.



Feb 18, 2014 at 12:01 PM
greenfield
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p.1 #20 · p.1 #20 · Yet Another Tamron 150-600 Thread! Interesting Observations --


pKai wrote:
As an engineer by training, I love and trust data, but as an artist by aspiration/inspiration, I like to subjectively look at stuff as well. Here, things got interesting



I assume camera(s) has been on a tripod while conducting your test.
Try again and do focus via LV and switch VC off unless done so ...
Also use mirror lockup and remote release (or internal timer release).
Make more than one shot for each f-stop and select the best of them.

This way you'd get more consistent and reliable results.


Edited on Feb 18, 2014 at 12:29 PM · View previous versions



Feb 18, 2014 at 12:06 PM
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