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Old 03-09-2008, 07:58 AM
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Hutech LPS P2 Front Filter Woes...

Hello all...
Received a Hutech LPS P2 Front Filter for my 40D last Friday, only managed to use it last night.
I've attached a stack of 5x10min subs - as you can see there's a severe vignetting effect on the image which was also present on each sub.


I've asked the supplier if I can replace the front filter with the old school 67mm version for the lens end of the camera instead - hopefully that will fix any vignetting issues.

This may be peculiar to lenses and may not occur when used with scopes, but I thought I might share so that we all learn.

Any other experiences/tales of woe!?

I found this article online in which an almost identical problem occurs with a different front filter...
http://www.saratogaskies.com/articles/ha-ff/index.html

...from the conclusions in the article, looks like the problem may be caused by internal reflections.

There are 2 ways to mount the filter so that the filter glass will be 2-3mm closer or further from the sensor - that may make a difference.

Cheers
Doug
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Last edited by dugnsuz; 03-09-2008 at 08:27 AM.
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Old 03-09-2008, 10:13 AM
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Thinking about this on the drive to work...
It's obviously a reflection of the rear element of the lens.
Is this fixable with flats?
Doug
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Old 03-09-2008, 10:16 AM
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RB (Andrew)
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Did you have a filter on the front of the lens?
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Old 03-09-2008, 10:25 AM
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Did you have a filter on the front of the lens?
No Andrew - just used the clip in front filter within the camera
Doug
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Old 03-09-2008, 01:09 PM
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Tandum (Robin)
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Does setting a custom white balance with the filter in place get rid of it from images?
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Old 03-09-2008, 02:02 PM
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Does setting a custom white balance with the filter in place get rid of it from images?
Not sure...
How would that work Robin?
Doug
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Old 03-09-2008, 03:20 PM
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I not sure either, but I'm using an astronomik front filter and my custom white balance shows vignetting similar to what your seeing. The raw file looks like it has a spot in the middle when converted to RGB in maxim. I don't get any distortion in images when using the CWB but I used to without it

I have attached my CWB file but this one looks a lot smoother out of PS than it does on screen in maxim. What do your normal daytime shots look like?
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Last edited by Tandum; 03-09-2008 at 03:41 PM.
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Old 03-09-2008, 03:47 PM
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Quote:
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I have attached my CWB file but this one looks a lot smoother out of PS than it does on screen in maxim. What do your normal daytime shots look like?
This is getting confusing! I thought this might be a physical problem due to internal reflections.

Is the attached file the one you use to set the CWB?
Daytime shots are fine with a CWB, but obviously the filter is not in the optical path then.

I'll experiment!

Doug
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Old 03-09-2008, 03:55 PM
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Yep Doug, it is definitly the rear lens of the scope, that is causing your problem, you would be better off ( yea I know this wont help now) with the Hutech filter screwed into the T-Mount Adapter.

I have a 72mm Hutech filter screwed to the rear element of the Tak, which works great, but I can also get away with a 48mm screwed into the T-Mount adapter, I use either.

If you like I could send up the 48mm one to you to give it a try, and if that fixes the problem than you have your answer.

Leon
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Old 03-09-2008, 03:58 PM
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Oh dear wrong answer, just realised your using a lens Doug. sorry

Leon
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Old 03-09-2008, 03:58 PM
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Yes, I took it with the filter in and a canon lens on the front, as the astronomik filter was turning everything blue. I get pretty reasonable daytime images using that CWB and with the filter in place.

After what you've said, I'm sort of thinking that the "hot spot" I see in the image in maxim is due to using a canon lens to get a CWB and it might go away if I can get a CWB image through the scope.

Will need to fiddle more here too.
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Old 03-09-2008, 04:10 PM
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Quote:
Originally Posted by leon View Post
Yep Doug, it is definitly the rear lens of the scope, that is causing your problem, you would be better off ( yea I know this wont help now) with the Hutech filter screwed into the T-Mount Adapter.

I have a 72mm Hutech filter screwed to the rear element of the Tak, which works great, but I can also get away with a 48mm screwed into the T-Mount adapter, I use either.

If you like I could send up the 48mm one to you to give it a try, and if that fixes the problem than you have your answer.

Leon
Thanks leon,
I've contacted the dealer in HK who I bought the filter from - hopefully he'll replace it with a 67mm filter and all will be well!
Before I send it back though, I'll try it out at different focal lengths and with my 50mm lens.
I can also reverse mount the filter so that the glass element of the front filter is a few mm further back from the rear lens element.
Otherwise I like the performance of these filters

Doug

Last edited by dugnsuz; 08-09-2008 at 04:49 PM. Reason: protecting the innocent!
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Old 03-09-2008, 04:37 PM
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No worries mate, I sure stuffed up that wonderful piece of advice,

Leon
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Old 03-09-2008, 04:39 PM
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Quote:
Originally Posted by dugnsuz View Post
- hopefully he'll replace it with a 67mm filter and all will be well!
Shame though because if you get another lens of different filter size you'll be stuck but I suppose you can use a stepdown ring.

I thought maybe it was internal reflection from perhaps a filter on the front of the lens like a 1A Sky filter or UV but as you say you're not using anything else.

I'd say try it the other way and see if it makes a difference before you exchange it because you're better off having it internal than one that is fixed at 67mm.
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Old 03-09-2008, 05:00 PM
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Quote:
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Shame though because if you get another lens of different filter size you'll be stuck but I suppose you can use a stepdown ring.
I'd say try it the other way and see if it makes a difference before you exchange it because you're better off having it internal than one that is fixed at 67mm.
Agreed - right now a 67mm is OK...it'll screw onto the 70-200mm f4 and I could use a 67-52mm step down for the nifty fifty. Problem arises if I get the 80mm refractor I've been promising myself
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Old 03-09-2008, 05:40 PM
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Quote:
Originally Posted by dugnsuz View Post
Agreed - right now a 67mm is OK...it'll screw onto the 70-200mm f4 and I could use a 67-52mm step down for the nifty fifty. Problem arises if I get the 80mm refractor I've been promising myself
You'd probably be better off with a 2" LPF like a Lumicon DSF when you use the camera at prime focus.

I had been wondering about vignetting with clipin front filters and so not bought one yet.
The 70-200mm has quite a wide cone at the image plain, I want to get a 70-200 f2.8 L IS with the AUD is right , did you see the same effect at longer focal lengths ?

I don't fancy buying a LPS-P2-82 at 349.00usd , the idea of these dropins (front filters) is to not need a different filter for different EF lenses.

Last edited by Ian Robinson; 03-09-2008 at 08:09 PM.
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Old 03-09-2008, 06:46 PM
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I'd like to see you resolve this rather than bypass it. I was looking at changing to one of these to solve my blue tint problems and an FF filter is definately the way to go.

I found this tip on the Hutech site :-
Front-mounted filters do not affect the camera's autofocus operation but, when installed, preclude the use of Canon EF-S lenses or some lenses designed for APS-C sized sensors. These filters also affect the closest focusing distance for each lens.

And this review does not describe any of the problems you have.

Last edited by Tandum; 03-09-2008 at 07:10 PM.
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  #18  
Old 03-09-2008, 09:08 PM
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I would have thought it to be internal reflections..
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Old 05-09-2008, 10:04 AM
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Update…
Managed to do a quick test last night.
Flipped the filter over so that the filter glass was now about 3mm further back from the rear lens element.
Attached pic shows the effects of the filter in its 2 different positions.

Left hand pic – filter closer to lens
Right hand pic – filter further from lens

The vignetting/reflection effect seems to be less defined and demarcated in the right hand pic – looks more like a vignetting effect that could be dealt with by flats.

I’m too lazy for flats though!!!
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  #20  
Old 05-09-2008, 02:46 PM
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UPDATE #2...
Dealer I bought the filter from has informed me that Hutech have discontinued the 67mm version of this filter, next size up is 72mm with a step down ring needed!!
Think I'll give the flats a go after all!!!!!

Although I may try a trade/wanted ad too

Cheers
Doug
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