1.4TC SHOWS NO LIGHT LOSS ??

[Bill McCrystyn]

My friend just got his new 7D and perplexed me saying he used a Tamron 1.4TC with his 400mmIS f/2.8 and had no stop loss. He told me Tamron advertised this and in fact it does meter that way. How is that possible?

[Axel Hildebrandt]

He probably has the non-reporting Tamron TC, it still loses a stop it's just impossible to see in the EXIF.

[Bill McCrystyn]

Thanks Axel. I told him being an OEM it probably just doesn't couple wirh the pins completly. Glass is glass. He insisted Tamron advertised it as not losing a stop. I guess I will look for a Tamron ad or spec and check it out.

[Axel Hildebrandt]

What they probably meant is that the camera would AF beyond specs, for example with this TC and 400f/5.6 on a xxD body but due to the extra glass the camera loses one f-stop of light. The AF performance is not as precise and the AF system tends to oscillate before locking. Tamron also has a reporting TC. The non-reporting one is cheaper.