[redbusa]

i have a large blue area in the middle of the image which seems to show more when using it as a standard lens than using it for macro. any ideas as to what the problem is with it?

[Lowell Goudge]

it may be sensor reflection

[pepperberry farm]

I've read several accounts of how the 52B and 52BB both exhibit this 'blue spot' issue, due to sensor reflection...

[TER-OR]

Are you using a hood? That might help reduce some reflections. Might.

[Skodadriver]

There are some other threads regarding the same problem.
Not sure how to link this thread but if you search the forums for this;

Tamron 90mm SP BBAR Problem


It will provide some info.

[redbusa]

thanks for replies, have just found a long discussion on the subject and you are correct. i have found that no spot occurs when i use a Teleplus 1.5x converter or since the sky has clouded over so will have to remember this in future. think i may keep my eye out for a Sigma 105 or maybe the present version of the Tamron.

[boriscleto]

thanks for replies, have just found a long discussion on the subject and you are correct. i have found that no spot occurs when i use a Teleplus 1.5x converter or since the sky has clouded over so will have to remember this in future. think i may keep my eye out for a Sigma 105 or maybe the present version of the Tamron.

Tamron made a nice 2X flat field TC that solves the problem...

[Skodadriver]

Tamron made a nice 2X flat field TC that solves the problem...

Or the extension tube...TAMRON EXTENSION TUBE 18F FOR TAMRON SP 90

[pepperberry farm]

or the 72B version of the Adaptall-2 lens - it does not seem to exhibit this issue....

[Thagomizer]

Or the extension tube...TAMRON EXTENSION TUBE 18F FOR TAMRON SP 90

Would the extension solve the sensor reflection problem? My understanding is that the Tamron's rear element is flat and acts like a mirror, reflecting the shine of the sensor back onto the sensor. I figure a TC would rectify this because it's introducing a non-flat optical element in front of the sensor: a simple extension tube would not. It would just be moving the flat, reflecting culprit further from the sensor. Is that enough to reduce the reflection?

[Skodadriver]

Would the extension solve the sensor reflection problem? My understanding is that the Tamron's rear element is flat and acts like a mirror, reflecting the shine of the sensor back onto the sensor. I figure a TC would rectify this because it's introducing a non-flat optical element in front of the sensor: a simple extension tube would not. It would just be moving the flat, reflecting culprit further from the sensor. Is that enough to reduce the reflection?

Good point and I don't know the answer to that.

[Lowell Goudge]

Would the extension solve the sensor reflection problem? My understanding is that the Tamron's rear element is flat and acts like a mirror, reflecting the shine of the sensor back onto the sensor. I figure a TC would rectify this because it's introducing a non-flat optical element in front of the sensor: a simple extension tube would not. It would just be moving the flat, reflecting culprit further from the sensor. Is that enough to reduce the reflection?

Good point and I don't know the answer to that.

note however that the extension tube will add some baffling of excessive light if it is well designed, and therefore may reduce the stray light that is giving you trouble.less light hitting the sensor will lead to less reflection. the same as diffuse light, and low contrast situations seem to also help. perhaps that is where the extension tube comes in, you are getting more diffuse light in a macro shot than a normal shot