[mst]

[quote name='Brightcolours' timestamp='1294143533' post='5341']

The lens is not reporting anything. [/quote]



Of course it is. Both Canon and Nikon lenses have integrated electronics and CPUs as well as electronic contacts. In both worlds, lenses report their specifications, including minimum and maximum focal length as well as minimum and maximum aperture, distance information, and probably lots of other stuff to the camera.



It's definitely the lens that reports the effective aperture to a Nikon camera. And of course "effective aperture" is not something that is unique to Nikon cameras and lenses. It's just that Canon chose NOT to display effective, but physical aperture instead, regardless of the focal distance.



[quote name='Brightcolours' timestamp='1294143533' post='5341']

I know, this sounds like a big "why would one want to do that", especially since smaller f-values with macro photography are not used for longer shutter times, but rather for more DOF. It would have been done with resolution tests in mind, to show better results on review sites....

[/quote]



Sure. Just like they've never been to the moon, right? <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/wink.gif' class='bbc_emoticon' alt='' />



Think about it again. If it worked that way, they'd have to decrease sensivity of the camera, not amplify anything.



And there's a simple test device to prove that the aperture is actually working as expected: the camera's DOF preview button <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/wink.gif' class='bbc_emoticon' alt='' />



-- Markus

[Brightcolours]

[quote name='mst' timestamp='1294146241' post='5343']

Of course it is. Both Canon and Nikon lenses have integrated electronics and CPUs as well as electronic contacts. In both worlds, lenses report their specifications, including minimum and maximum focal length as well as minimum and maximum aperture, distance information, and probably lots of other stuff to the camera.



It's definitely the lens that reports the effective aperture to a Nikon camera. And of course "effective aperture" is not something that is unique to Nikon cameras and lenses. It's just that Canon chose NOT to display effective, but physical aperture instead, regardless of the focal distance.







Sure. Just like they've never been to the moon, right? <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/wink.gif' class='bbc_emoticon' alt='' />



Think about it again. If it worked that way, they'd have to decrease sensivity of the camera, not amplify anything.



And there's a simple test device to prove that the aperture is actually working as expected: the camera's DOF preview button <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/wink.gif' class='bbc_emoticon' alt='' />



-- Markus

[/quote]

That makes little sense. If you can adjust the amplification to more amplification, of course you can adjust the amplification to less amplification too.



You can of course see that the aperture gets smaller, with the DOF button. Of course you can, but you can not just see it is f22 instead of f22. you will have to do comparisons.



Fact is that it is impossible to ignore the difference in measurements between the Canon and the Nikon test, something is going on. The peak resolution with the Nikon is already reached a stop later, and then the f11 from Canon is very close to what you measure at f22 for the Nikon test. That is not normal, the lens is of the same design.



So, I would suggest to compare f22 on the Canon and Nikon versions, visually, as a starting point to investigate the weird difference in measurements.



To illustrate:

Canon EF-S 60mm f2.8 USM macro on 8mp 350D:



Canon EF-S 60mm f2.8 USM macro on 15mp 50D:



Sigma 70mm f2.8 EX DG macro on 8mp 350D:



Tamron 60mm f2.8 Di II SP macro on 15mp 50D:





Nikon AF 60mm D micro on 10mp D200:



Nikon AF-S 60mm f2.8G N Micro on 10mp D200:



Tamron 60mm f2.8 Di II SP macro on 10mp 200D:





We can see it is NOT your way of measuring, as the Nikon 60mm lenses show "normal" curves, like Klaus gets with the Canon, the Sigma and the 60mm Tamron. And you are not the only one getting odd measurements for the Nikon mount version:

http://www.tamronlensreview.com/tamron60macroreview



Canon mount version however:



http://www.bobatkins.com/photography/reviews/tamron_60mm_f2_macro_review1.html



Although, there is also this review, with 50D results closer to yours than what Klaus found:



http://translate.google.com/translate?hl=en&sl=auto&tl=en&u=http%3A%2F%2Freview.fengniao.com%2F143%2F1431893.html



It keeps on puzzling me (as you can note <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/wink.gif' class='bbc_emoticon' alt='' /> ).

[mst]

[quote name='Brightcolours' timestamp='1294150871' post='5344']

That makes little sense. If you can adjust the amplification to more amplification, of course you can adjust the amplification to less amplification too.[/quote]



Yep. That would be Nikon's part. To make a Tamron lens look better in lens reviews. Makes much more sense, doesn't it?



[quote name='Brightcolours' timestamp='1294150871' post='5344']

You can of course see that the aperture gets smaller, with the DOF button. Of course you can, but you can not just see it is f22 instead of f22. you will have to do comparisons.[/quote]



Of course I can not see if f/22 is really f/22, but I can see that the aperture closes more with any stop I choose, the exposure changes accordingly, the exposure data is the same as with similar lenses (like the AF-S 60). So, to my eyes, this lens closes down to f/22.



[quote name='Brightcolours' timestamp='1294150871' post='5344']

So, I would suggest to compare f22 on the Canon and Nikon versions, visually, as a starting point to investigate the weird difference in measurements.

[/quote]



From all the ideas I already had (believe me, I've spend endless hours with this lens already ... and a few of its cousins) this is the only one I couldn't check. Send me the Canon mount version (and a Canon camera) and I'll check.



However, I'm afraid, I already know the outcome ...



-- Markus

[Klaus]

Technically it doesn't really matter all that much. I do somehow suspect that f/22 is actually f/16 (and f/2 may be actually f/1.7 or whatever) or so but from a user perspective the images are still sharp at f/22 thus the measurements reflect this. The only relevant aspect is probably just a lack of depth-of-field.



Klaus







[quote name='mst' timestamp='1294152712' post='5345']

Yep. That would be Nikon's part. To make a Tamron lens look better in lens reviews. Makes much more sense, doesn't it?







Of course I can not see if f/22 is really f/22, but I can see that the aperture closes more with any stop I choose, the exposure changes accordingly, the exposure data is the same as with similar lenses (like the AF-S 60). So, to my eyes, this lens closes down to f/22.







From all the ideas I already had (believe me, I've spend endless hours with this lens already ... and a few of its cousins) this is the only one I couldn't check. Send me the Canon mount version (and a Canon camera) and I'll check.



However, I'm afraid, I already know the outcome ...



-- Markus

[/quote]