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Film DSO photography with RBG filters

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#1 PABresler

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Posted 19 June 2019 - 11:33 PM

I just realized I could potentially save a thousand dollars or more on a CMOS mono camera by using film with RGB, and maybe even H alpha and O III filters. I am picking up a Canon EOS on Ebay for $50.00 (along with a 400 mm lens!) I already have RGB filters. I do darkroom work, and can develop the film myself. I also have a photo film scanner, which I have used for conventional photography. I figure using Tri-X 400 iso film.

 

So, I get some subs with each filter, develop and scan the negatives, and then stack them with Photoshop ..right? With ISO 400 film I would need 8 minute exposures for equivalency to 2 minutes at ISO 1600 with a DSLR.

 

What do you think?

 

Peter

 



#2 PDB

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Posted 20 June 2019 - 02:17 AM

Hi Peter,

 

not exactly. Film has what is called Reciprocity failure (Schwarzschild effect). See this wikipedia article look at the last paragraph https://en.wikipedia...y_(photography)

 

Many years ago, Kodak produced some special emulsions (103a series) to overcome this. (But these were costly, difficuylt to get (special orders) had to be kept refrigirated, and were fairly grainy)

 

So yes, you method will work. Has been done in the past (even in Darkroom without computer) but be prepared for much longer exposures than you might expect. (been there before the digital revolution)

 

Regards,

 

Paul


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#3 Todd N

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Posted 20 June 2019 - 03:06 AM

This isn't going to work as you anticipate primarily for what Paul has stated about reciprocity effect especially with off the shelf B&W film though some do work well enough. Blue and green bandpass filters or even a LPF kills film performance for typical B&W film other than something like the long gone Techpan. For B&W you are better off going full spectrum and forget color filters other than perhaps yellows to cut chromatic abberation if applicable. Off the shelf Tri-X is not a good choice. Ilford HP5 is way better.  If your insistent on color then use color film. Many Kodak films are sensitive to H-alpha and may perform well enough. I recommend using a color ISO 400 or 800 film and do many(4 to 6) five or ten minute exposures depending on the target  and then scan and sum them together to lesson grain. Color films have less grain than their B&W ISO equivalent and have way less reciprocity. I haven't used them but I would try Kodak Porta 400 & 800, Cinestill 800(Kodak color motion picture film) to get started.

 

I forgot to add that narrowband filters like OIII or UHC don't work on film; I've tried it. Plus, films like Tri-X and HP5 have negligible H-alpha sensitivity.

 

 

Todd


Edited by Todd N, 20 June 2019 - 03:11 AM.


#4 PABresler

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Posted 20 June 2019 - 03:10 AM

Would you gain anything over using a DSLR or low end color camera like the Orion G3 ( which I own)?

 

Peter



#5 Todd N

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Posted 20 June 2019 - 03:22 AM

Would you gain anything over using a DSLR or low end color camera like the Orion G3 ( which I own)?

 

Peter

Do you mean is there anything to gain using film over a DSLR or CCD?For the most part, no. Digital has superior performance and doesn't suffer reciprocity. I'm not familiar with the Orion G3. Unless it's modded a DSLR isn't going to have a lot of H-alpha sensitivity so that would limit it's use with such a filter. Galaxies and Globular clusters look better from stock cameras, IMO. It's hard to beat that $50 price point for a DSLR so, I can't even recommend buying a film camera which would be more expensive. Considering buying new though, a film camera could be way cheaper(<$200) and have a larger full frame than a smaller CCD/CMOS camera. That could be considered some limited advantages.

 

I shoot film because I like the look of particularly B&W and prefer the color rendition of film over DSLR's which look almost cartoon-like to me which I dislike despite the better resolution.


Edited by Todd N, 20 June 2019 - 03:26 AM.


#6 PABresler

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Posted 20 June 2019 - 03:25 AM

Just to get things straight...the $50.00 was for a film camera  I do own a modded T3I and an un modded 6D



#7 PABresler

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Posted 20 June 2019 - 03:26 AM

I was just speculating about getting mono quality on the cheap!



#8 Todd N

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Posted 20 June 2019 - 03:31 AM

Just to get things straight...the $50.00 was for a film camera  I do own a modded T3I and an un modded 6D

I would encourage you then to try film.



#9 PABresler

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Posted 20 June 2019 - 03:34 AM

So you suggest using color film?



#10 Todd N

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Posted 20 June 2019 - 03:46 AM

So you suggest using color film?

 

Well, that's up to you. I gave my recommendations in post #3. B&W is easy to develop at home and you will need a film scanner but it's more practical to send color film out to a lab for processing.



#11 PDB

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Posted 20 June 2019 - 04:41 AM

Nostalgia ...

 

Early in the 70's some German amateurs made some stunning pictures using film and tri-color techniques. Could find something about it the S&T archives:

https://archive.org/...08-cbr/page/n51

https://archive.org/...11-cbr/page/n59

 

Paul



#12 Michal1

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Posted 20 June 2019 - 09:14 AM

I just realized I could potentially save a thousand dollars or more on a CMOS mono camera by using film with RGB, and maybe even H alpha and O III filters.

Choose film only if your intention is specifically using film. Using film might be simpler only if you use a color film, wide field lenses and short exposures. Which doesn't mean that such photos aren't nice. Some tips:

https://stargazerslo...rolls-question/



#13 Nightfly

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Posted 20 June 2019 - 12:14 PM

Its an old post, but still applicable.   I had forgotten about it!  



#14 TxStars

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Posted 20 June 2019 - 11:04 PM

If you are looking to have a try at it there is no reason not to do it.

Sure it will not match digital cameras, but you can still learn something, and have fun doing it..

Look at the spec sheets of some films to get an idea of what they can and can not record.

 

*  I still manually guide a photo from time to time, just to stay in practice.



#15 PABresler

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Posted 20 June 2019 - 11:05 PM

What film do you suggest?



#16 Nightfly

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Posted 21 June 2019 - 11:51 AM

Acros would be terrible for the red channel.

Dave Malin made tricolor astrophotographs that were wonderful. He used Kodak spectroscopic films I believe.

#17 TxStars

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Posted 21 June 2019 - 03:34 PM

You could try using Tri-X or T-Max for Blue and Green, and a color film like Kodak Portra for the red..

Depending on sky condition and lens speed exposure times will need to be bracketed.

With filters 15 / 20 / 25  min for a start till you get some data to adjust times from.



#18 PABresler

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Posted 21 June 2019 - 04:02 PM

Its easier to use just one type of film for all the filters. What do you suggest? Color negative film with filters actually could be used. I do have a film scanner, and would use that for initial processing.

 

Peter



#19 TxStars

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Posted 21 June 2019 - 04:59 PM

You would need to look and see what the band pass of your filters are.

Then compare that to a films spec sheet to see if there is "One" that will work for all the filters.



#20 Todd N

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Posted 21 June 2019 - 06:32 PM

Its easier to use just one type of film for all the filters. What do you suggest? Color negative film with filters actually could be used. I do have a film scanner, and would use that for initial processing.

 

Peter

 

Using color filters with color film doesn't make sense with the possible exception of using a red to highlight Ha. Each separate color layer is in essence a filter since they pass a limited portion of the spectrum to make up the RGB channels of a color picture.



#21 Nightfly

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Posted 21 June 2019 - 06:52 PM

Rick Thurmond used hypered Tech Pan and Acros for tri-color work.

 

http://www.rickthurm...om/Astrophotos/

 

Rick is a master of his craft.  Tri-color astrophotography is daunting.   I for one will not be attempting it.  Exposures are long and work flow is difficult.  I'd stick with color film.


Edited by Nightfly, 21 June 2019 - 06:53 PM.

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#22 Michal1

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Posted 22 June 2019 - 03:36 PM

Using color filters with color film doesn't make sense with the possible exception of using a red to highlight Ha. Each separate color layer is in essence a filter since they pass a limited portion of the spectrum to make up the RGB channels of a color picture.

Agreed. Unless the way is the goal ;) . Tricolor astrophotography was used because Tech Pan or Acros had a much lower reciprocity failure than color films.



#23 Todd N

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Posted 22 June 2019 - 06:36 PM

Agreed. Unless the way is the goal wink.gif . Tricolor astrophotography was used because Tech Pan or Acros had a much lower reciprocity failure than color films.

 

I've never seen a tri-color image using Acros only . I once tested a Baader green color  filter with Acros and the details are a bit fuzzy being so long ago. But, I think I did a ten minute exp. on my C8 @f/6.5, It didn't turn out very good and just reinforced the futility of trying to do film color composite images. I think the rule for Techpan tri-color work was to double the exposure times for the green and blue images. Yikes!



#24 Michal1

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Posted 23 June 2019 - 03:29 AM

Rick Thurmond experimented with Acros, see the link posted by Nightfly. Rick wrote the details in older posts in this forum. If I remember well, he used Acros for the green and blue channels and TP for the red channel.



#25 Todd N

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Posted 23 June 2019 - 12:46 PM

Rick Thurmond experimented with Acros, see the link posted by Nightfly. Rick wrote the details in older posts in this forum. If I remember well, he used Acros for the green and blue channels and TP for the red channel.

Yes, Rick  did great film work with a C14 I believe.




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