Difference between Tamron SP and non-SP center-pinch lens caps?

For years I’ve been using Tamron center-pinch caps (for example, B&H part TALC52) on my LF lenses. They’re much less likely to come off accidentally because they engage the filter threads.

Today I discovered there’s now an “SP” version, but I can’t figure out how the two styles differ other than the newer style being “for SP lenses”. A visit to tamron.jp was uninformative.

I’m after a cap for a very wide angle lens with a large and highly curved front element, and am concerned about the cap possibly touching the front glass.

Does anybody know the difference between these two cap types beyond their styling? I’m specifically looking at B&H parts TA95MMFLC and TA95FLCSP.

I’m also open to other suggestions for an appropriate positive-fitting cap.

I have in the past taken an extra skylight filter removed the glass and threaded a screw in cap into the filter ring. I put a few drops of finger nail polish on the threads of the cap and filter ring first and let them dry a few days first. Gives positive protection to the lens. It is hard to know how much clearance you have with out doing possible damage.

Most of the time this will work and I may end up doing it eventually (does anyone have a junk 95mm filter they’d like to donate to the cause?) but I’m currently wrestling with a real challenge. I’m trying to photograph a very specific subject that requires the absolute extreme limits of movements on my 5x7 (with 4x5 reduction back). I can just make it with no filter mounted, but I get very slight corner vignetting with just a 95-105 step-up ring, nearly unusable vignetting when I screw on a 105mm filter, and even worse still if I use a 95mm filter without the step-up. So an empty 95mm filter used as a lens-cap spacer needs to be removable, but as it's still more stuff to deal with in the poison-ivy patch it's a non-starter, at least right now.

I’m hoping an answer to my original question will guide me to the right lens cap.

"SP" was Tamron's designation of their upper class Adaptall-lenses in the 80's and means "Super(ior) Performance".

I do not see that SP lenses needed different caps. Instead I assume "SP"-caps are just caps bearing that SP-designation and came with the respective SP-lens.

Steve Goldstein said:

For most applications this will work and I may end up doing that eventually (does anyone have a 95mm filter they’d like to donate to the cause?) but I’m currently wrestling with a real challenge. I’m trying to photograph a very specific subject that requires the absolute extreme limits of movements on my 5x7 (with 4x5 reduction back). I can just make it with no filter mounted, but I get very slight corner vignetting with just a 95-105 step-up ring, nearly unusable vignetting when I screw on a 105mm filter, and even worse still if I use a 95mm filter without the step-up.

I’m hoping an answer to my original question will guide me to the right lens cap.

Click to expand...

So use a 105mm lens cap on the step up ring? Secure the lens cap to the ring and just unscrew the whole thing.

cramej said:

So use a 105mm lens cap on the step up ring? Secure the lens cap to the ring and just unscrew the whole thing.

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Yes, that's very likely what I'll do since I have the ring and a snap-in 105mm cap. It's a little less convenient, but will do the job.

Steve, you did not reply on my SP comment. How did you get to that SP designation?
The only hint I finally found is that term used by B&H themselves, which seems rather erratic to me, as I do not see it on the cap itself, not even as model-code.

Yes, I got it from the BH listings. Its styling is a bit more sleek but I really wonder why Tamron were willing to tool up a second version.

I sent a question off to Tamron USA and will report back anything I learn.

For LF lenses (or any lenses) with exposed front elements, the best answer is probably a push-on lens cap, which is what these lenses originally came with, and which provides more clearance than a snap-on cap. B&H sells push on lens caps. I don't know what the right diameter is for your lens, but it's probably the 100mm lens cap (measure OD of the lens front element, not the filter thread). There aren't a lot of choices for such big lenses so you might have to shim it with a bit of tape. The stock caps are not terribly expensive and you can even get custom sized caps elsewhere on the web. For example: Kaiser 100mm push on cap, https://www.bhphotovideo.com/c/product/125306-REG/Kaiser_206900_100mm_Push_On_Lens_Cap.html

Heliopan offer a great variety of push-on caps. Their largest sizes are 85, 90, 100, 120mm.

Steve Goldstein said:

Does anybody know the difference between these two cap types beyond their styling? I’m specifically looking at B&H parts TA95MMFLC and TA95FLCSP.

Click to expand...

Not seeing much. There might be a slightly longer flange on the SP that slips into the lens, so it might be a little better at keeping out junk, but mostly, it looks like the SP mechanism is redesigned to be easier to manufacture.

As others have mentioned, the Kaiser caps are good for slip-on, and I use the "Breakthrough Photography" center-pinch caps.