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Macro wide open - ??



 
 
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  #2  
Old June 1st 18, 04:30 PM posted to rec.photo.digital
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Default Macro wide open - ??

In article , android
wrote:

Why does my macro lens (Tamron SP90) open up to 2.5?


Does it ? as it seems to state f2.8 on the web.


It could be that the firmware of the camera has access to the lense T
value in its database. PC uses a fairly modern EOS 6D mark II, IIRC.
There is according to DxO Mark two different Tammies 90SP one T/3.0 and
the other, newer T/3.3. The latter would be more like 2.5 rather than 2.8
if the former is used for reference... HTH!


or it could actually be f/2.5
http://www.adaptall-2.com/lenses/52B.html
  #4  
Old June 1st 18, 04:40 PM posted to rec.photo.digital
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Posts: 24,165
Default Macro wide open - ??

In article , android
wrote:

Why does my macro lens (Tamron SP90) open up to 2.5?

Does it ? as it seems to state f2.8 on the web.

It could be that the firmware of the camera has access to the lense T
value in its database. PC uses a fairly modern EOS 6D mark II, IIRC.
There is according to DxO Mark two different Tammies 90SP one T/3.0 and
the other, newer T/3.3. The latter would be more like 2.5 rather than
2.8 if the former is used for reference... HTH!


or it could actually be f/2.5
http://www.adaptall-2.com/lenses/52B.html


Sure. But that would not be reported from lense to camera.


he didn't say it was reported to the camera.

he only asked why it opens up to f/2.5, which is for a shallow depth of
field and/or low light, like any other lens.
 




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