Attention Tamron 24-70 VC owners

Started Jul 28, 2012 | Discussions thread
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Horshack OP Veteran Member • Posts: 5,803
Some clarification of the experiment outcomes

Just to clarify, my first post about this issue where I demonstrated f/2.8 vs f/4 images of the test chart had the f/4 image at 1/2 the shutter speed, so the two images should have had nearly identical brightness (exposure reciprocity) yet the f/4.0 image was twice as bright, indicating that the lens did not stop down properly.

In the experiment I asked you to perform, I asked you keep the shutter speed constant between the f/2.8 and f4 images, so the expected outcome in that case was for the f/4 image to be half as bright.

Both experiments are testing the same thing but the expected outcome is different.

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