Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
04-07-2018, 04:24 AM   #1
Forum Member




Join Date: Jun 2017
Location: Cambridge
Posts: 93
Reversing Hoya Filters...? (DA 21)

Apologies if this is in the wrong forum....

Following some recent sea silliness, I have just had to carefully clean a very salty front element on my DA 21 - my fault entirely. It seems to have survived and I am now looking at using a filter in the future to prevent potential damage in the future - the question:

Using a 43mm filter inside the stock hood on a DA 21 requires it to be screwed in, in reverse (i.e. the side that is normally facing the lens is now facing the outside world) - does this matter? Are filters coated on both sides?

This is the specific filter being used...

HOYA | The Difference is Clear

Thanks in advance!

04-07-2018, 06:23 AM   #2
Loyal Site Supporter
Loyal Site Supporter




Join Date: Feb 2010
Location: Maryland
Posts: 595
I have done exactly the same. I think that is decent filter and the rear mounting does require it to be screwed into the rear of the hood. To my knowledge the "outer" and "inner" coatings are the same. I have never seen any problems with the mounting you suggest. Some will argue that you shouldn't use any filter on the limiteds but for dusty, salty and wet conditions, I think it is prudent.
04-07-2018, 06:33 AM   #3
Pentaxian
photoptimist's Avatar

Join Date: Jul 2016
Photos: Albums
Posts: 5,113
Hmmm... it's not clear.

Test 1: If you hold the filter almost edge-on, does the front surface reflect light differently than the back surface?

Test 2: If you apply a drop of water to the filter surface, does it bead just as much on the back or front surface?

Or a solution: If the front and back surfaces are different, can you reverse the glass? Many filters are constructed either with a screw-in retaining ring or a stiff split-ring clip/spring. If so, you can take the filter apart, reverse the glass and make it so that the magic anti-static, scratch-resistant, water-repelling side is where it needs to be for your DA21.
04-07-2018, 08:34 AM   #4
Veteran Member
Saltwater Images's Avatar

Join Date: Nov 2014
Location: Newfoundland
Photos: Gallery
Posts: 501
I use the Hoya Pro1D Protector inside the HD DA 21 hood. No issues. Works perfectly.

04-07-2018, 08:50 AM   #5
Moderator
Not a Number's Avatar

Join Date: Mar 2012
Location: Venice, CA
Posts: 10,510
Budget or bargain filters if coated at all may be coated on only one side. No way to tell except by careful examination.
04-07-2018, 09:08 AM   #6
Forum Member




Join Date: Jun 2017
Location: Cambridge
Posts: 93
Original Poster
QuoteOriginally posted by photoptimist Quote
Hmmm... it's not clear.

Test 1: If you hold the filter almost edge-on, does the front surface reflect light differently than the back surface?

Test 2: If you apply a drop of water to the filter surface, does it bead just as much on the back or front surface?

Or a solution: If the front and back surfaces are different, can you reverse the glass? Many filters are constructed either with a screw-in retaining ring or a stiff split-ring clip/spring. If so, you can take the filter apart, reverse the glass and make it so that the magic anti-static, scratch-resistant, water-repelling side is where it needs to be for your DA21.
Thanks all for the responses, I hadn't thought about flipping the glass as a solution - good thinking! I will do some testing and then try this if there seems to be a difference.
04-07-2018, 10:25 AM   #7
Site Supporter
Site Supporter




Join Date: Jun 2008
Location: Idaho
Photos: Gallery
Posts: 2,360
Most good filters (like Hoya) are coated on both sides, in most cases with the same type anti-reflection coating which consists of a number of thin layers and sometimes a hard topcoat. Even if coated on only one surface, flipping the filter will have little if any effect on the image since it just moves those surfaces to slightly different positions but doesn't change what they do.

04-07-2018, 11:29 AM   #8
dms
Site Supporter
Site Supporter




Join Date: Aug 2011
Location: New York, NY
Photos: Gallery
Posts: 2,192
QuoteOriginally posted by Bob 256 Quote
Most good filters (like Hoya) are coated on both sides, in most cases with the same type anti-reflection coating which consists of a number of thin layers and sometimes a hard topcoat. Even if coated on only one surface, flipping the filter will have little if any effect on the image since it just moves those surfaces to slightly different positions but doesn't change what they do.
I don't think this is correct--as regards filters with only a single side coated. I believe it is reflections off the lens front element that cause the problem, and thus the filter side facing the lens is the important one as regards presence or absence of coating.
04-07-2018, 03:41 PM - 1 Like   #9
Site Supporter
Site Supporter




Join Date: Jun 2008
Location: Idaho
Photos: Gallery
Posts: 2,360
QuoteOriginally posted by dms Quote
I don't think this is correct--as regards filters with only a single side coated. I believe it is reflections off the lens front element that cause the problem, and thus the filter side facing the lens is the important one as regards presence or absence of coating.
It really doesn't matter which way an uncoated side is facing - reflections from that uncoated surface are the same regardless of the direction the light comes. One way, the reflections have to go through a layer of glass and the other way they don't but the reflections are a function of the air-glass interface and don't care which is first or second.

If you take a piece of window glass (uncoated) and observe the reflections (actually two - one from each air-glass surface), then flip the glass around, nothing will change - same with a filter. The surface producing the noticeable reflections (uncoated side) will move a bit further away, but it will do the same thing reflection-wise. Reflections from front mounted filters would be a non-issue if it weren't for the reflection of the lens elements that follow which can bounce light back toward the filter. Otherwise, the only reflections from the filter would be away from the lens & camera, and wouldn't do anything. Inter-lens/filter reflections are what causes halos, ghosting, etc. (along with a few other things like reflections off iris blades etc,).

Another reason for coating lenses and filters is to enhance their transmission of light. Any light reflected cuts down on what goes through the lens - for regular window glass, that can be 10% or more. When reflection is reduced, transmission increases by a like amount. Again, however, there is no advantage here based on which side is coated; 90% one way - 90% flipped.
04-08-2018, 06:39 AM   #10
Pentaxian




Join Date: Apr 2007
Location: Oklahoma USA
Posts: 2,192
1. The main issue with having to reverse a filter is that I don't believe a polarizer will work when reversed (at least not a CPL, not sure about an LPL) so reversing for that is not a workable solution - you would have to reverse the mounting.

2. Due to my recent experience with the MeFoto filters (in the Price Watch discussion), I've concluded that it's impossible (for me, at least) to determine if a filter is coated or multi-coated. I used to go by the various colored reflections that most anti-reflection coatings produce, but at least according to MeFoto, their polarizers are two-layer coated on both sides for improving transmission. They don't say anything about anti-reflection properties of the coating. Their UV filters on the other hand have the traditional multi-colored look I'm accustomed to from anti-reflection multi-coatings.
04-08-2018, 04:11 PM   #11
Veteran Member
Saltwater Images's Avatar

Join Date: Nov 2014
Location: Newfoundland
Photos: Gallery
Posts: 501
QuoteOriginally posted by tibbitts Quote
1. The main issue with having to reverse a filter is that I don't believe a polarizer will work when reversed (at least not a CPL, not sure about an LPL) so reversing for that is not a workable solution - you would have to reverse the mounting.

2. Due to my recent experience with the MeFoto filters (in the Price Watch discussion), I've concluded that it's impossible (for me, at least) to determine if a filter is coated or multi-coated. I used to go by the various colored reflections that most anti-reflection coatings produce, but at least according to MeFoto, their polarizers are two-layer coated on both sides for improving transmission. They don't say anything about anti-reflection properties of the coating. Their UV filters on the other hand have the traditional multi-colored look I'm accustomed to from anti-reflection multi-coatings.
With my set of HD DA Limited’s - I only have one good 49mm polarizer and one good 49mm variable ND. Both filters work on The DA Limited’s plus the D FA 100 Macro WR. All of these lenses have a 49mm filter thread. On the 21 Limited once you remove the bayonet hood, the lens itself has 49mm thread. Put your polarizer on there and a 49mm pinch cap. Problem solved.
04-08-2018, 11:43 PM - 2 Likes   #12
Forum Member




Join Date: Jun 2017
Location: Cambridge
Posts: 93
Original Poster
Hoya got back to me. Hopefully this helps to clarify things. Thanks again for all the advice.

Thank you for contacting us.

We would like to inform you that the way to reverse attach of the filter is not affect the filter's performance since the filters are coated equally on both sides.

Thank you for your continuous support.

Best regards,
Ken H.
Tokina/HOYA supporting unit, Kenko Tokina Co., Ltd

Last edited by tbelf; 04-08-2018 at 11:44 PM. Reason: Typo
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
da, filter, future, hoya, tripod
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
For Sale - Sold: Pentax SMC DA* 16-50mm f/2.8 AL SDM IF ED + HOYA UV(C) - HOYA Circ-Pol - HOYA Warm libbe Sold Items 3 02-03-2017 08:35 PM
Filters, Filters, and more Filters! alamo5000 Photographic Technique 7 12-18-2016 08:36 AM
For Sale - Sold: Hoya ND filters and Cir-polarizng filters and more... TOUGEFC Sold Items 3 08-09-2012 04:10 AM
DA 21 LE vs CARL ZEISS DISTAGON T* 21/2.8 ZF yipchunyu Pentax SLR Lens Discussion 4 10-06-2009 06:51 PM



All times are GMT -7. The time now is 11:02 PM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top