Step Up / Down Ring. Whadda I need?

[BrandonSi]

I bought a few filters for the 50mm 1.8 lens, and I'd like to use them on my 300d kit 18-55mm lens. I tried buying some conversion ring and I either got it backward or I just totally bought the wrong one.

I believe the 50mm filter size is 52mm, and the kit lens 58 mm. Do I step up or down?

Does one normally buy filters in the largest lens diameter and then step down?

[weemannie]

That would mean you need to step down:)

The problem you will must likely have is vignetting. Normally, you should buy filters for the largest diameter lens and step up rings for the others.
So in your case, buy a 58mm filter and a 52mm to 58mm step up ring.

[etaf]

i thnk that would cause problems on the 18mm end a d you will have corners cut off the image.
try holding it up close to - NOT touching in the centre of the lens and see the effect at the 18mm end before you go out and buy a conversion ring

[ron chappel]

Yes one usually buys a bigger size and adaptes them to the smaller lens,but you can try them.

To test them on the kit lens -
- hold a filter on the front and snap a pic of blue sky.
You'll see straight away if it's going to cause darkening of the corners. The short end of the zoom with the aperture wide open will be the most likely place it will show .

The ring you'll need to fit these to the kit lens is a 58mm-52mm step down ring
**They are allways named with the lens size first then forward to the filter size**.
So a filter bigger than the lens' filter thread will need a step up ring.
A filter smaller than the lens' filter thread will need a step down ring

[BrandonSi]

The ring you'll need to fit these to the kit lens is a 58mm-52mm step down ring
**They are allways named with the lens size first then forward to the filter size**.
So a filter bigger than the lens' filter thread will need a step up ring.
A filter smaller than the lens' filter thread will need a step down ring

I'm gonna print that out and put it in my pocket until I get it :)

I actually didn't think about buying the larger filters and stepping up/down/left until posting this thread, so at least I have concept nailed for future purchases!

[robertwgross]

The rule is to consider the light coming toward the camera lens, and consider the filters and lenses in that order. You can use a 58mm filter and step down to a 52mm lens.

You would not want to think in reverse and want to step up from a 52mm lens to a 58mm filter.

---Bob Gross---

[ron chappel]

Sorry Bob,that's back to front.
Actually you had me doubting myself as i do make fundamental mistakes;)

I double checked and all the rings i looked at are measured lens side first

[robertwgross]

Sorry Bob,that's back to front.

I guess all of mine must be made backwards then.

---Bob Gross---

[MTalley]

I have the same two lenses. I also happened to have a bunch of 52mm filters left from my previous P/S camera. I purchased a stepdown ring off Ebay to go from 58 to 52mm. I took the attached picture with the kit lens, stepdown ring and my Sunpak Cicular Polarizer (52mm) at full wide (18mm). Notice the vignetting.

Since I use CP's much more often than any other filter, I went ahead and picked up a CP for the kit lens (58mm) and the Tamron 75-300 lens (62mm) off Ebay. Since I got a good price from the seller on those, I went ahead and got some UV's for lens protection on each.

Edited to add: This particular combo (kit lens/stepdown/52mm CP) will not cause any vignetting if you keep the lens between about 27mm on out to 55mm zoom.