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Old 25-04-2020, 08:22 PM
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Outcast (Carlton)
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Clip-in LP filters - Need some advice please

I've recently purchased a Samyang 14mm f2.8 Ultra Wide angle lens which is paired with an unmodified Canon EOS 70d.

I'm using it for Ultra widefield milky way shots & at present, due to the various restrictions in place I'm having to shoot from my moderately light polluted backyard.

I'm dealing with skyglow from highway & suburbs to the South/South West which is intruding into the lower right of my shots as well as generally reducing my overall contrast & detail.

Can anyone recommend a clip in LP filter to improve my images...

Attached are 3 sample images, straight out of the camera, no processing applied, in order:

30sec @ ISO 3200
25sec @ ISO 4000
20sec @ ISO 4000

Images are untracked
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Last edited by Outcast; 27-04-2020 at 09:43 PM.
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  #2  
Old 27-04-2020, 09:34 PM
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Outcast (Carlton)
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Anyone used a Svbony CLS, clip in or screw on... same glass, same result I presume...

I only want it for if I'm mucking around with the camera in the backyard...

Svbony is nice cheap option at around $80 for a clip in compared with $199 for the Astronomik version or $350 plus for an Optolong L-Pro... but..., I'd rather not blow $80 if it's a rubbish option...

Anyone at all got any experience with these or any other filters that are available in a clip in version for Canon EOS please...
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Old 28-04-2020, 08:58 AM
JA
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Quote:
Originally Posted by Outcast View Post
Anyone used a Svbony CLS, clip in or screw on... same glass, same result I presume...

I only want it for if I'm mucking around with the camera in the backyard...

Svbony is nice cheap option at around $80 for a clip in compared with $199 for the Astronomik version or $350 plus for an Optolong L-Pro... but..., I'd rather not blow $80 if it's a rubbish option...

Anyone at all got any experience with these or any other filters that are available in a clip in version for Canon EOS please...
With the Samyang 14mm f/2.8 an in-camera filter is really the only option given the size of the front element and angle of view, but before you buy I'd encourage you to try hard with the no filter option, as I can see some structure in the Milky Way even in the lower-res sample images posted, which may be able to be improved significantly with:
  • Multiple exposure stacking*
  • Exposure to the Right
  • Processing to reduce the appearance of the light pollution

The reason I say that is because I have been amazed with what it is possible to see in the night sky, even from my light polluted backyard, SQM 18.8 mag/arcsec^2 ..... i.e:Bortle Heaps), even with a non-modified DSLR and the above techniques and your sky looks darker to me.

Happy hunting

Best
JA

* Stacking Wide angle lens images will be more challenging, but thankfully the Samyang 14mm f/2.8 is, in the samples I've seen, very low in image abberations at the extremes AND you will not be using all of the image circle of the lens as you will be using it on a crop body DSLR. Given the huge field of view, just watch out for unwanted light at the edge of the frame (street light, etc), which can in certain situations cause image ghost/flare.

Last edited by JA; 28-04-2020 at 09:25 AM.
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Old 28-04-2020, 11:07 AM
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Outcast (Carlton)
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Thanks JA,

many thanks for your advice & encouragement,

I am still playing with the processing however, I've found that to tease out anymore significant detail I have to overstretch the histogram & the end result is not particularly pleasant....

I have tried some stacking but, will look more closely at trying that again.

I don't quite understand the 'Exposure to the Right' point, would be grateful if you could explain that a little more.

Cheers

Carlton
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Old 28-04-2020, 12:52 PM
JA
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Quote:
Originally Posted by Outcast View Post
Thanks JA,

many thanks for your advice & encouragement,

I am still playing with the processing however, I've found that to tease out anymore significant detail I have to overstretch the histogram & the end result is not particularly pleasant....
I'm not sure if you are talking about a single image in that experience, seems as though you might be in light of your comment below, BUT the end result will improve significantly with stacking compared with a single image. It may be more challenging at 14mm f/2.8, but the fact that you are using a cropped camera means you won't see all of the image circle from the lens and hence fewer edge aberrations.

Also were you shooting in RAW or JPEG when you mentioned the end result not being "particularly pleasant"?

Quote:
Originally Posted by Outcast View Post
I have tried some stacking but, will look more closely at trying that again.
I am always amazed with what a good camera, lens, stacking and processing can dig out. I too have a Samyang 14mm f/2.8, but I've only ever used it for Landscape photography so far, preferring a slightly longer 35mm and 50mm on fullframe for most nightscapes. In any event for your next session with the Samyang 14mm on a moonless night: I would try just as you already have 20 second exposures at ISO 3200 (and perhaps also try ISO6400) shooting in RAW, but this time collect as many of them as you dare. Go nuts 30, 40, 50 whatever.... Then stack them in SEQUATOR which has rudimentary light pollution reduction built in, if you engage it as well as stacking the stars and keeping any landscape component (ground) "frozen", once you tell it where the ground is. Sometimes you get some funky glows around ground objects, but experiment and you'll be amazed.
Quote:
Originally Posted by Outcast View Post
I don't quite understand the 'Exposure to the Right' point, would be grateful if you could explain that a little more.

Cheers

Carlton
Exposure to the right, ETTR as some call it, is about trying to obtain a strong image signal, and hence higher Signal to Noise ratio, by pushing the histogram to the right hand side, so that those very faint nebulous structures we all love to see in a final image, are not buried in the left hand tail of the histogram or truncated by insufficient exposure. The histogram is pushed to the right by as much exposure as possible without over exposure. But it is all a balancing act you want the lens wide open, to collect as much light as but on the other hand don't want the aberrations that that sometimes brings with it. You want long exposure length but not so much as to cause trailing if you are on a fixed tripod.

Oh BTW if you are stacking images on a fixed tripod you are also getting a form of dithering without any effort, since the stars are changing their position on the sensor (both during any given exposure and more importantly also from exposure to exposure).

Best
JA

Last edited by JA; 28-04-2020 at 01:13 PM.
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Old 28-04-2020, 05:55 PM
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Outcast (Carlton)
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Thanks again JA

All very useful information...

Just to clarify, I'm shooting in RAW with as much turned off in the camera as possible.

I did some earlier shots at only 13 sec @ ISO 800 which I stacked in both DSS (just to see what happened) & also in Affinity Photo. As these were pretty short exposures, the stacking wasn't as effective as it might have been plus, due to the movement of the stars over the range of shots, the foreground then came up somewhat fuzzy... I do have Sequator but, as yet, I haven't explored it.

The latest round shot at far higher ISO's & much longer exposures are also shot in Raw, I think I've probably just been a bit heavy handed when trying to process resulting in a somewhat overstretched histogram & an image result that just doesn't look good (can't think how else to put it sorry). I think I just need to be a bit more subtle with the sliders & spend a bit more time closely examining each step's results before moving on to other processing options.

I assume with the ETTR method you've discussed we are looking predominantly at the exposure level in post processing to 'move' the histogram to the right & then look at things such as contrast & brightness, black levels, etc...

All being shot on a fixed tripod at this stage & very much just beginnning to experiment. My skies to the east are somewhat darker as we back onto a reserve & the inlet is in that direction, hence less sky glow... might focus on that area as well to see what pops out in slightly darker skies...

Fortunately, dark skies aren't very far away here in Cairns... about 10 minutes down the road & I can get away from most of the light.. just hasn't been so much of an option with the current crop of restrictions in place but, they are about to eased so, popping down the road becomes an option again.

As you suggest, I'll keep experimenting for a bit, I love the FOV the Samyang gives, even if it is only on a crop sensor... it's unbelievably wide.. I have a 50mm f1.8 available too so, might give that a run... the whole thing largely acts as something fun to do when I don't feel like setting up a full on imaging rig or even a visual scope.. I'm mesmerised by some of the really widefield images I've seen on here & other sites, keen to see what I can produce for myself..

Might keep my money in my pocket for now...

Cheers

Last edited by Outcast; 28-04-2020 at 09:30 PM.
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Old 28-04-2020, 07:15 PM
raymo
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On the subject of LP filters, as far as I know, all light pollution filters put a colour cast on images that has to be removed during processing. Having said that, I have a new Svbony CLS filter that arrived after I stopped doing AP.
You can have it for $55 including postage. PM me if you're interested.
raymo
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