Minolta "WHITE" caps
I'm not sure how many of you may have gotten a white rear lens cap with your lens, but they are a little different than the usual black ones.
For one thing, they have a protruding blade on the inside that actually actuates the aperture blades as you tighten it down, until the aperture was set wide open.
Here it is on the SONY 50mm f/1.4 and the SONY CZ 135mm f/1.8
Also, if your lens is 135mm or longer, you can actually get an image to present on the rear cap, by manual focusing to sharpness.
The scene with the lens
The scene ... in the lens! :D
Just a little something extra to think about with these older Minolta "WHITE" caps.
Why do you want to store your lenses with the aperture open??
I guess it keeps the spring working ... and also looks cool on the display shelf. You have one of those in the house, don't you? You know, for your equipment, when you unload your backpack and are not toting it all around with you. :)
lol interesting, wouldn't that stretch out your spring, by keeping it compressed?
dr4gon ... this is a Minolta-design.
I think they knew what they wanted to do ... so, I'm good with it.
... just questioning they're logic. ;) (well since it is no longer around)
The old black ones are the same. I have a Sony Cap (not sure how) that is the same as well.
Obviously this design is bad for the spring, but I think it relieves pressure on the Iris Blades.
I did a check of all my back caps and all of them have it as well.
As I twist the rear lens cap on all my Sony lenses and look down the front end I can also see the aperture blades open and close on them. Now on the other hand it is not that way with my Tamron lenses with their rear caps.
Yep ... oops ... the black ones, too. How did that rascal get by me? The TAMRON caps do not .. and guess who has a whole lot of TAMRON caps? :o It's just that the white ones make the aperture blade movement so obvious ... I thought I'd mention you also can get a clear, focused image with some of the longer lenses.