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Any advantages shooting astrophotgraphy with film over digital?

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#26 Nightfly

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Posted 27 November 2017 - 08:22 PM

Peter,

 

It's been a dogs age.   Nice to see you posting again and with a nice round of images.

 

A few of us are still shooting film in one fashion or another.  Not bothering to post images, but glad to see yours.



#27 ClownFish

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Posted 28 November 2017 - 01:36 AM

Hey James!

 

Yes, I have been away for quite a while. Since I was last in New Mexico, I did three years in Pakistan, one in Iraq, two in Singapore, and three in Budapest Hungary - all very light polluted - which is a no no for film work.  Now I starting two years in Kampala Uganda, a country where 80% of the country has no electricity, but here in the capitol there is LP.  So I also am starting down the digital road now.. as it's just about the only way to do decent work in light polluted skies.  I packed up a new iOptron CEM25P mount, Loderstar CCD guider and a Williams Optics Star71 to match my Canon 6D.  I have them all connected wireless to my Macbook Pro via a small lightweight Stellarmate and use EKOS software to run the works.  I may pop on my trusty Olympus OM-1 occasional just to grab some film shots from time to time.

 

I also just bought a 15 acre ranch in New Mexico - so when I stop tramping around the world in 2019 I can build another observatory there.

 

Can't wait!

 

Peter


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#28 WillCarney

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Posted 30 November 2017 - 06:22 PM

The biggest difference is time.  I took some excellent pictures of the Orion Nebula with film.  I have yet to equal that with DSLR.  With the DSLR you have to take hours and hours of exposures.  Including lights, darks, flats etc.  Then spend hours processing.  With film it is getting harder to find processors.  I still have one Pentax camera I use from time to time.  I had at one time two Pentax Super Programs and two Praktica FX3.  The FX3 was great since it never froze or had batteries that died.



#29 17.5Dob

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Posted 07 December 2017 - 12:44 AM

The biggest difference is time.  I took some excellent pictures of the Orion Nebula with film.  I have yet to equal that with DSLR.  With the DSLR you have to take hours and hours of exposures.  Including lights, darks, flats etc.  Then spend hours processing.  With film it is getting harder to find processors.  I still have one Pentax camera I use from time to time.  I had at one time two Pentax Super Programs and two Praktica FX3.  The FX3 was great since it never froze or had batteries that died.

Lol ! I started taking my first AP's back in the Tri-X days of the late 60's. I never got a decent Orion image.

I took this shot 2 weeks ago using an "old" Nikon D5300. No darks, flats ,or bias.

2 1/2 hrs of 6 min subs @ ISO 200. Maybe an hour of processing, the same as film.

 

27062734359_7a68f56a41_c.jpg


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#30 seriousfun

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Posted 21 June 2018 - 02:15 AM

It is a long time since I shot film and I guess most are in the same boat.

 

Modern film shooters are lucky in that they can incorporate digital technology to assist them with auto guiding and locating targets with goto, ensuring the subject is nicely framed.  

 

 

I recall the days of trying to locate a galaxy or nebulosity fainter than the telescope could detect and hoping that I had it framed right before sitting in the cold making manual corrections over the following 60 mins as my precious faint light rays accumulated on the ever increasingly unresponsive emulsion.

 

But the joy of the result in those halcyon days far exceeded the "hmmm thats got promise" response the unprocessed digital images produces.

 

Even so, I'd never go back.  The end results now achievable, justify the means.


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#31 SandyHouTex

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Posted 21 June 2018 - 06:10 PM

25 microns?  That number surprises me -- it's 1/40mm or 20 line pairs per millimeter.  I notice the specs for Acros 100, for example, are 40 lpm (12.5 microns) at a contrast of 1.6:1, and 200 lpm (2.5 microns) at a contrast of 1000:1.  Where does the discrepancy come from?

Yes, you are correct.  The big advantage to film is resolution.  Mr. Mcovington is incorrect.  Velvia 100’s resolution is 160 lines per mm (lpm).


Edited by SandyHouTex, 21 June 2018 - 06:12 PM.


#32 SandyHouTex

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Posted 21 June 2018 - 06:16 PM

MTF is a more common way to specify in my experience. I was looking at the Kodak Elite Chrome 200 data sheet just before I posted above. It specifies MTF curves for each emulsion layer but does not give target contrast numbers. I looked at other data sheets for Kodak films. Same thing. Fuji also specifies MTFs in addition to target contrast numbers for all of their current consumer films. (I also looked at some Ilford spec sheets. No resolution spec at all. Oh well.)

Here’s a calculation for Velvia.  Resolution is 160 lpm:

 

https://kenrockwell....-resolution.htm



#33 SandyHouTex

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Posted 21 June 2018 - 06:17 PM

Hello, everyone,

 

I am no longer into film astrophotography having boxed up my Honeywell Pentax Spotmatic many years ago but I raised an interesting subject over in the DSLR group and someone suggested I post it here.

 

Has anyone ever compared the mechanics of a 35mm film camera lens iris and shutter design to those of a DSLR? Until a few days ago I never considered this until I began comparing some photos I took of the 1970 total eclipse in Virginia where I captured a striking image of the diamond ring effect to what DSLR cameras being used today have tried to do.

 

Looking at everyone's eclipse photos I just realized how bland and flattened the diamond ring affect appears when photographed with modern DSLR cameras. I was so excited in planning to venture 400 miles south to shoot the August 21st eclipse with a whole array of high tech equipment that I rented but last minute problems caused my plans to unravel and I had to stay home. I was very fortunate to witness the 1970 total eclipse in Virginia and photograph it with my trusted Spotmatic 35mm camera with roll film, although with only a 200mm prime telephoto lens. And the striking appearance of the diamond ring effect that I captured must have been because of the design of the shutter and iris in the camera which modern cameras don't have.

 

I am far from being an expert on the subject but I would be interested in reading some comments.

 

Regards,

Nelson

I love the detail in the corona.  Can’t get that with digital.



#34 SandyHouTex

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Posted 21 June 2018 - 06:20 PM

The biggest difference is time.  I took some excellent pictures of the Orion Nebula with film.  I have yet to equal that with DSLR.  With the DSLR you have to take hours and hours of exposures.  Including lights, darks, flats etc.  Then spend hours processing.  With film it is getting harder to find processors.  I still have one Pentax camera I use from time to time.  I had at one time two Pentax Super Programs and two Praktica FX3.  The FX3 was great since it never froze or had batteries that died.

You’re in luck.  Films making a comeback.

 

It’s also true that film’s sensitivity can be increased by hypering with hydrogen gas, or cooling, just like they do now with dedicated astro cameras.  Back in the day we used dry ice.


Edited by SandyHouTex, 21 June 2018 - 07:09 PM.


#35 Shakedown St.

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Posted 22 June 2018 - 12:55 AM

Wow I'm looking back at this thread I posted last year, amazing shots!

 

The big thing for me is, with film you would not have to worry about hot pixels. You would not have to invest in a cooled CCD sensor, or build mechanisms to cool your DSLR. I imagine bigger film like medium and large format would be more sensitive to light and give you a higher resolution.

 

It is something I've always wondered about and wanted to do successfully, partly because of costs too. High resolution color CCD sensors can be very costly. Seeing pictures like that motivates me to try film again. I have a Bronica S2, it makes you wonder if I could somehow get that mounted to one of my scopes.


Edited by Shakedown St., 22 June 2018 - 12:59 AM.


#36 ClownFish

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Posted 22 June 2018 - 03:18 AM

Last week, I shot 80 exposures and after processing, the result was less than a single 40 minute exposure on film.  Yes, the detail was better, and the stars much smaller, but the image appeared flat.

The film shot I was comparing it to was guided by HAND, so the accuracy was very poor compared to using a Lodestar X2!  Also, I was tracking with a low cost wobbly LXD75 mount.  I wonder now how a highly accurately tracked 30 minute color image would look today using my guiding equipment on the accurate CEM25P.  

 

The other film downside is that the whole exposure has to be one shot.  Have the tracking off 20 minutes in, and you have to start over.

Polar alignment is critical.  Dec errors continue to multiply until the whole image is rotated.  In digital, you only need your alignment to allow perfect DEC tracking for as long as one sub.

In film, it must be perfect - ideally with zero DEC corrections - for the whole long exposure.  In a home observatory, that is not too difficult, but in the field, can be really hard to get.

 

Got satellites or planes?  You cover the the objective (without touching the scope) until the offending object passes by.  You can'y rely on post processing to remove the streak.

 

Also - with film, a truly dark sky is needed.  Filters to cut light pollution do not work well, and most film is very sensitive to light pollution.

 

I still have my trusty OM1 camera.  I may try it when I get to a really dark site again.



#37 hfjacinto

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Posted 22 June 2018 - 08:28 AM

 

. I imagine bigger film like medium and large format would be more sensitive to light and give you a higher resolution.

 

It is something I've always wondered about and wanted to do successfully, partly because of costs too. High resolution color CCD sensors can be very costly. Seeing pictures like that motivates me to try film again. I have a Bronica S2, it makes you wonder if I could somehow get that mounted to one of my scopes.

Wonder what would be more costly a big chip CCD or a telescope that can illuminate a Medium/Large film Format camera.


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#38 SandyHouTex

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Posted 22 June 2018 - 09:04 AM

Wow I'm looking back at this thread I posted last year, amazing shots!

 

The big thing for me is, with film you would not have to worry about hot pixels. You would not have to invest in a cooled CCD sensor, or build mechanisms to cool your DSLR. I imagine bigger film like medium and large format would be more sensitive to light and give you a higher resolution.

 

It is something I've always wondered about and wanted to do successfully, partly because of costs too. High resolution color CCD sensors can be very costly. Seeing pictures like that motivates me to try film again. I have a Bronica S2, it makes you wonder if I could somehow get that mounted to one of my scopes.

Medium format film only buys you a larger field of view.  The reolution of film and sensitivity to light doesn’t change.  And since most scopes don’t have huge highly corrected and flat fields of view, I’m not sure it buys much.  To see what film can do just look at the pictures taken with the 48” Schmidt camera at Palomar.  It’s a curved focal surface, but the results are astounding.  With auto-guiding, amatuer equipment could do almost as good.

 

The dirty little secret about DSLRs is how they burn through their camera shutter counts so quickly.  Dark frames, subs, etc. etc..  I’ve heard of people reaching their cameras tested shutter limit in 3 or 4 years.  Throw it away and buy another camera.



#39 Shakedown St.

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Posted 22 June 2018 - 05:25 PM

My 6X6 medium format negatives are four times the size of a 35mm negative. That means they can be scanned at four times the resolution without adding considerable grain. Of course you are also limited to the resolution of your optics. Large format negatives can be blown up drastically larger, they were used by advertsing companies for billboards in the city.

Edited by Shakedown St., 22 June 2018 - 05:34 PM.


#40 Shakedown St.

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Posted 22 June 2018 - 05:41 PM

The other film downside is that the whole exposure has to be one shot. Have the tracking off 20 minutes in, and you have to start over.
Polar alignment is critical. Dec errors continue to multiply until the whole image is rotated. In digital, you only need your alignment to allow perfect DEC tracking for as long as one sub.
In film, it must be perfect - ideally with zero DEC corrections - for the whole long exposure. In a home observatory, that is not too difficult, but in the field, can be really hard to get.

Got satellites or planes? You cover the the objective (without touching the scope) until the offending object passes by. You can'y rely on post processing to remove the streak.


On my old scope I would get star drift after more than four minutes of exposure so it does concern me, but had an interesting proposal. Stacking short exposure shots on film like you would a digital file, after scanning them into your computer as a light file. I wonder what the results would be, and if that would even work.

#41 Michael Covington

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Posted 22 June 2018 - 07:22 PM

On my old scope I would get star drift after more than four minutes of exposure so it does concern me, but had an interesting proposal. Stacking short exposure shots on film like you would a digital file, after scanning them into your computer as a light file. I wonder what the results would be, and if that would even work.

I have done it.  It's a great way to reduce grain.  It also can increase dynamic range if you stack exposures of different lengths.

 

All the exposures have to be long enough to show appreciable detail.  Because film images are nonlinear, they do not stack additively the way digital images do.


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#42 Shakedown St.

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Posted 22 June 2018 - 07:57 PM

I have done it.  It's a great way to reduce grain.  It also can increase dynamic range if you stack exposures of different lengths.

 

All the exposures have to be long enough to show appreciable detail.  Because film images are nonlinear, they do not stack additively the way digital images do.

I see, what would you say is the shortest exposure you could take with film? Let's say, two minute exposures?



#43 Michael Covington

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Posted 22 June 2018 - 09:02 PM

I see, what would you say is the shortest exposure you could take with film? Let's say, two minute exposures?

Depends on the f-ratio and the speed and reciprocity failure of film.  Bear in mind that because of reciprocity failure, if you can get into the film's usable response range in 2 minutes, it is much better to take ten 2-minute exposures than one 20-minute exposure.

 

At f/2.8 with some light pollution, you might find 2 or 5 minutes sufficient.  Light pollution can actually help overcome "inertia" at the low end of the film's response.


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#44 Shakedown St.

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Posted 22 June 2018 - 10:38 PM

I'll be bringing it up to our local astronomy club, very far up into the wilderness. I think it would be a good opportunity to find out, very low light pollution.

 

Problem is I feel my mount would not track for twenty minutes without introducing star movement, it would be very trial and error.


Edited by Shakedown St., 22 June 2018 - 10:39 PM.


#45 Uwe Pilz

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Posted 23 June 2018 - 12:01 AM

>  At f/2.8 with some light pollution, you might find 2 or 5 minutes sufficient.  Light pollution can actually help overcome "inertia" at the low end of the film's response.

 

I have some old negatives of M57 and M13, mad with an 6 inch Mak, around f/12 from suburb. I think the light pollution effect to overcame the interial of the film has played a role her. I gave the photographs one or two minutes with TMZ 3200 film. 


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#46 SandyHouTex

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Posted 23 June 2018 - 09:56 AM

My 6X6 medium format negatives are four times the size of a 35mm negative. That means they can be scanned at four times the resolution without adding considerable grain. Of course you are also limited to the resolution of your optics. Large format negatives can be blown up drastically larger, they were used by advertsing companies for billboards in the city.

For film, the resolution is usually specified in lines per millimeter.  So the resolution for 35mm film is the same as medium format.  I have a couple of Pentax 645Ns, and while the area they capture is wider for a given lens focal length, the resolution is still the same.  For Fuji Velvia it’s 160 lpm in both 35mm and the 120 rolls I use in my 645Ns.



#47 Michael Covington

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Posted 23 June 2018 - 10:27 AM

What blows my mind would be that, somebody had told me that a 50 minute film exposure is equivalent to a 1 minute digital exposure because film only has a 1% quantum efficiency. I really don't buy that, looking at those gorgeous 30 minute film exposures.

Film does have lower quantum efficiency, but the main factor at work there is reciprocity failure.  1 minute vs 50 minutes might be appropriate for a film with low quantum efficiency and high reciprocity failure, such as Tri-X Pan.  My experience (thinking of pictures of M31 at f/4) is that 20 minutes on film look like 1 minute on digital; that's with Ektachrome 200, pushed.

Films like Tri-X follow a three-for-two rule in exposures longer than a few seconds: to double the effective exposure, you have to triple the actual exposure.  Witih some newer films it's more like five-for-four.  Reciprocity failure is terribly costly!  It's the biggest reason for moving to digital imaging.


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#48 Shakedown St.

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Posted 23 June 2018 - 11:57 AM

Sorry about that, website froze last night and posted same responce three times. Woops!

Edited by Shakedown St., 23 June 2018 - 12:00 PM.


#49 Todd N

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Posted 23 June 2018 - 06:40 PM

My 6X6 medium format negatives are four times the size of a 35mm negative. That means they can be scanned at four times the resolution without adding considerable grain. Of course you are also limited to the resolution of your optics. Large format negatives can be blown up drastically larger, they were used by advertsing companies for billboards in the city.

A few have already made this point that larger format in and of itself doesn't translate to greater resolution. The implication is to compare larger format with a proportionally higher focal length to that of 35mm with a comparable field of view.. The larger format then has higher resolution due to the image being magnified(higher focal length) while the grain(noise) is smaller in relation to details over 35mm.



#50 sparksinspace

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Posted 24 June 2018 - 07:20 AM

I think its a lot like vacuum tube amplifier's  vs transistor amps. cant get that richness and roundness of sound with a transistor.


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