Tamron SP 90mm f2.8 Macro

[Steveo_Hants]

I have bought one of these lenses from ebay and I received it today. I am using it on a D50, but not sure if I have a problem. When I select aperture priority I can only get it to go down to f3 on the D50 display. Any ideas? Its NOT the newer Di version of the lens.

[unclerichy]

When looking for review of that lens I saw mention of it being 2.8 but showing 3 on the camera but I can't recall whether that was the Di or not. Have a google.

FWIW the Di version doesn't on my D50 :)

[Matt]

Have a look at the exif to see what aperture is reported.

[Steveo_Hants]

Have a look at the exif to see what aperture is reported.

Showing on exif as f3

[Steveo_Hants]

Ok this is seriously bugging me now! At the infinity focus end of the range I can only get it to close down to f3 as I said before, but when I focus down to 1:1 I can only get the lens to close down to f6! Is something wrong?

[Joe T]

It may be reporting the "effective aperture" of the lens, which changes as you get closer to 1:1. Im sure someone else can explain it better than I can?

[photo-request]

hi, ive got the lens, and was told it only goes down to 3 on digital but 2.8 on film hope it helsp

[Steveo_Hants]

hi, ive got the lens, and was told it only goes down to 3 on digital but 2.8 on film hope it helsp

Ok so that sorts that one out, what about the max aperture at 1:1? Does yours only go up to f6 as well?

[Joe T]

http://photo.net/bboard/q-and-a-fetch-msg?msg_id=009S3Y

and

These are the effective apertures set on the camera, not marked apertures on an aperture ring. As you focus more closely you lose light up to two stops at life size. Nikon AF cameras calculate this automatically. When I say f/32 on the camera it equates to f/16 on the lens at life size. Just set your modern SLR to f/32 at the camera and don't worry. I have more about this under bellows factors below.

From http://www.kenrockwell.com/tech/macro.htm

The selected lenses all have different maximum effective aperture and image magnification. I have compiled the relevant data for these lenses in the table below. Please note that for such close-up shooting conditions, there can be a great discrepancy between nominal and effective aperture. Remember f-numbers are specified for infinity focus

From: http://www.naturfotograf.com/need_speed01.html

HTH

[Steveo_Hants]

Cheers Joe, I found this too CLICK HERE (http://www.velocityreviews.com/forums/t242191-re-help-tamron-sp-90mm-f28-behaves-like-a-variable-aperture-zoom.html)