Pentax HD 20-40 Ltd filter size issue

dcsorrell · 09-28-2016, 01:01 PM

My new lens arrived. Filter size is supposed to be 55mm, but even a 49 mm filter is too big. I've already returned a different lens due to QC issues. Now what am I supposed to do?

Adam · 09-28-2016, 01:10 PM

Not sure what to say- the filter size is definitely 55mm if you want to fit it between the hood and lens. Note that this isn't a particularly common size, with more filters being 58mm or 52mm.

aleonx3 · 09-28-2016, 01:10 PM - **1 Like**

I have this lens... yes, the filter size is 55mm how is it possible that a 49mm filter is already too big, just curious? Can you show a picture of it when you try to fit a 49mm filter? If you mount the filter, it has to be mounted first before putting the lens hood on. FYI... I don't use filters for my lens.

dcsorrell · 09-28-2016, 01:21 PM

Originally posted by aleonx3

I have this lens... yes, the filter size is 55mm how is it possible that a 49mm filter is already too big, just curious? Can you show a picture of it when you try to fit a 49mm filter? If you mount the filter, it has to be mounted first before putting the lens hood on. FYI... I don't use filters for my lens.

Oh... I feel sheepish...

One more issue, though... the camera reads the widest aperture as 3.5, or either the aperture isn't opening up completely. ??

**Kevin B123** · 09-28-2016, 01:25 PM

Originally posted by dcsorrell

Oh... I feel sheepish...

One more issue, though... the camera reads the widest aperture as 3.5, or either the aperture isn't opening up completely. ??

It's a variable aperture lens, it will only be f2.8 at 20mm to somewhere around 25mm I think.

dcsorrell · 09-28-2016, 01:26 PM

Never mind; I figured it out. User error. (No more drama, I promise!)

---------- Post added 09-28-16 at 01:28 PM ----------

Originally posted by Kevin B123

It's a variable aperture lens, it will only be f2.8 at 20mm to somewhere around 25mm I think.

Thanks..(sheepish again.... Baaa...)

atcoombs · 09-28-2016, 02:49 PM

On the subject of filters for the 20-40, I use a 67mm step up ring that lets me use 67mm filters for both the 20-40 and the 60-250mm.

**microlight** · 09-28-2016, 04:08 PM

I'm another one who doesn't use filters on any lens, including the 20-40...

dcsorrell · 09-28-2016, 06:17 PM

I about can't live without my polarizer, but my UV is only for protection. I noticed today that my filter is much more dust resistant than the lens, as well.

09-28-2016, 01:01 PM	#1
dcsorrell New Member Join Date: Sep 2016 Location: North Carolina Posts: 18	Pentax HD 20-40 Ltd filter size issue My new lens arrived. Filter size is supposed to be 55mm, but even a 49 mm filter is too big. I've already returned a different lens due to QC issues. Now what am I supposed to do?

09-28-2016, 01:10 PM	#2
Adam Administrator Site Webmaster Join Date: Sep 2006 Location: Arizona Photos: Gallery \| Albums Posts: 51,594	Not sure what to say- the filter size is definitely 55mm if you want to fit it between the hood and lens. Note that this isn't a particularly common size, with more filters being 58mm or 52mm. Adam PentaxForums.com Webmaster (Site Usage Guide \| Site Help \| My Photography) PentaxForums.com server and development costs are user-supported. You can help cover these costs by donating or purchasing one of our Pentax eBooks. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, KEH, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

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09-28-2016, 01:10 PM - 1 Like	#3
aleonx3 Veteran Member Join Date: Jul 2007 Location: Brampton, Ontario Photos: Gallery \| Albums Posts: 3,996	I have this lens... yes, the filter size is 55mm how is it possible that a 49mm filter is already too big, just curious? Can you show a picture of it when you try to fit a 49mm filter? If you mount the filter, it has to be mounted first before putting the lens hood on. FYI... I don't use filters for my lens.

09-28-2016, 01:21 PM	#4
dcsorrell New Member Join Date: Sep 2016 Location: North Carolina Posts: 18 Original Poster	Originally posted by aleonx3 I have this lens... yes, the filter size is 55mm how is it possible that a 49mm filter is already too big, just curious? Can you show a picture of it when you try to fit a 49mm filter? If you mount the filter, it has to be mounted first before putting the lens hood on. FYI... I don't use filters for my lens. Oh... I feel sheepish... One more issue, though... the camera reads the widest aperture as 3.5, or either the aperture isn't opening up completely. ??

09-28-2016, 01:25 PM	#5
Kevin B123 Loyal Site Supporter Join Date: Jul 2016 Location: Hampshire Photos: Gallery \| Albums Posts: 3,176	Originally posted by dcsorrell Oh... I feel sheepish... One more issue, though... the camera reads the widest aperture as 3.5, or either the aperture isn't opening up completely. ?? It's a variable aperture lens, it will only be f2.8 at 20mm to somewhere around 25mm I think.

09-28-2016, 01:26 PM	#6
dcsorrell New Member Join Date: Sep 2016 Location: North Carolina Posts: 18 Original Poster	Never mind; I figured it out. User error. (No more drama, I promise!) ---------- Post added 09-28-16 at 01:28 PM ---------- Originally posted by Kevin B123 It's a variable aperture lens, it will only be f2.8 at 20mm to somewhere around 25mm I think. Thanks..(sheepish again.... Baaa...)

09-28-2016, 02:49 PM	#7
atcoombs Senior Member Join Date: Jan 2007 Posts: 124	On the subject of filters for the 20-40, I use a 67mm step up ring that lets me use 67mm filters for both the 20-40 and the 60-250mm.

09-28-2016, 04:08 PM	#8
microlight Site Supporter Join Date: Sep 2011 Location: Hampshire, UK Posts: 2,129	I'm another one who doesn't use filters on any lens, including the 20-40...

09-28-2016, 06:17 PM	#9
dcsorrell New Member Join Date: Sep 2016 Location: North Carolina Posts: 18 Original Poster	I about can't live without my polarizer, but my UV is only for protection. I noticed today that my filter is much more dust resistant than the lens, as well.