Fast Wides vs "slow" wides and night photography

[FredrickSummers]

Fredrick, it can be done. I've been working with and using my 4x5 camera for astrophotography for just about a decade now. One of the lenses I keep on hand for the sole purpose of astrophotography is the Nikon 90mm f/4.5. For sharp, pin-point stars across the entire frame, it's no good wide open at 4.5. Sorry. Every time I've tried it wide open stars take on a UFO-like shape in the corners due to diffraction in the lens. However, once stopped down to f/8 the lens is really good, corner to corner. If this also corresponds to the similar but slower 90mm f/8 Nikkor used wide open at f/8 I can't say. I don't have one of those lenses. But I can confirm the 4.5 works nicely once stopped down.

I've never done star trails with the 90mm f/4.5. It may very well be just fine wide open for that.

I've attached two images below. One is a equatorial setup I use for the camera. The other is the result (taken with the Nikon 90mm f/4.5 lens.)

Attachment 153990 Attachment 153991

And we have a winner! WOW, that is AMAZING! May I ask which film you use for that? I have been kicking around one of the geo tracking set ups, but I couldn't find much info that wasn't digital specific. It looks like an expensive set up!

Knowing how they perform as points of light tells me all I'd need to know about how it would perform for star trails (I don't think points of light is possible still without the tracking set-up though, not without the ability to get a very high ISO).

[Corran]

What equatorial mount do you use (brand, model)? I've been very close to purchasing a nice German equatorial mount several times but stopped myself. I think I will soon, perhaps also with a telescope to go with.

The UFO or batwing shaped stars in the corners I believe is called coma. Very common on my older fast primes on 35mm when shot wide-open or near. I wonder if the modern aspherical LF lenses have made that issue go away. I have yet to try my Schneider 90mm XL for stars which is my newest wide-angle but I guess it's still not aspherical. The 80mm Super-Symmar is.

[FredrickSummers]

What equatorial mount do you use (brand, model)? I've been very close to purchasing a nice German equatorial mount several times but stopped myself. I think I will soon, perhaps also with a telescope to go with.

The UFO or batwing shaped stars in the corners I believe is called coma. Very common on my older fast primes on 35mm when shot wide-open or near. I wonder if the modern aspherical LF lenses have made that issue go away. I have yet to try my Schneider 90mm XL for stars which is my newest wide-angle but I guess it's still not aspherical. The 80mm Super-Symmar is.

It is Coma, and even many modern lenses have it wide open. Oddly Rokinon/Samyang a low cost and fairly cheap built lenses are the lowest to exhibit it even wide open at 1.4! This is what I was asking about the fast wides. My Fuji 210 didn't appear to have any, but I did such a terrible job trying I doubt I could tell either. They are not as bad doing trails.

On a related note the oddest coma I have had is my Minolta 17-35G wide open (3.5) it's huge and looks like the batman symbols at the far counters!


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[konakoa]

Fredrick, Corran; I’m using two films currently. Both are black and white. One is Fuji Acros. The other is gas hypersensitized Kodak Tech Pan that I started using last year. I had to build the “hypering” system entirely from scratch. For no-fuss results, use Acros. It’s fantastic, fantastic stuff for low light, moonlit landscape, and astrophotography. The image I posted previously was made on Acros.

I used to shoot color, but have put all my efforts into black and white as I can print that in my darkroom. Still, astrophotography on a big color 4x5 transparency can be a beautiful thing. Attached below is one I did many years ago.

The equatorial mount is a Vixen GP2. It’s a nice and simple little mount that sadly isn’t made any more. They go for a few hundred bucks used. It’s perfect for my needs as I wanted something small, compact and not computerized. Another option would be a Losmandy GM-8, (still being produced new) should you be similarly inclined.

Corran, you might be interested to hear I have tried an aspherical lens for stars. A Schneider 150mm XL. Long story short, it also suffers from coma (thanks for the correct term) as well. In the center, perfectly sharp. Stars are nice and round. Go out to the edges of the frame, they’re smeared. I really, really, wanted the 150 XL to perform wide open at 5.6 yet it has the same “UFO” problems as my Nikon 90mm f/4.5. Perhaps moreso. I have a Schenider 150mm HM waiting in the wings to be tried when I can get a break in the weather.

[Corran]

Thanks, I'll take a look at those mounts. Interesting that the asperical lens didn't perform. I've got to try my 90mm and 72mm XL lenses one of these days. Too much rain lately.

I haven't tried shooting startrails with b&w for years. I love the color aspect. I've heard of hypering, that's pretty neat.

[Pfsor]

I would challange that as well from experience. I have shot stars with digital, and my best lens was (well, I do still have it) the Minolta 16mm fisheye. I also had a Rokinon 35mm f1.4 which has a huge "real aperture" but, if I stoped it down to f2.8 and the Minolta wide open, even with the same exposure the starts were slightly brighter, but there were more of them (within the same area). I have tried it on a number of lenses and the "real aperture" as you call it was not the determining factors. I also never said the lens was for that purpose, just that it was a consideration of getting faster over slower. If I'm buying a lens I may as well consider all potential uses of it, at least that is my idea. I do have my digital kit (two actually, a6000 for night I normally use my Rokinon 12mm f2 which is quite impressive of a lens) as well as my A99 which a handfull of lenses. I used the a99 this past winter to conduct a test between various 50mm for the mount, and the one with the SMALLEST "real aperture" the 50mm f2.8 macro, actually had the best performance and most visible stars. You do also realize that its not just how bright, but a faster lens will pick up more starts within the given time, right? That, coverage (coverage is normally measured at f22, how bad is fall of at larger apertures), and flare charastics is what I was asking for on that part. Do you have any star/star trail images from large format to share?

Now when you're comfortably seated in your - my experience is more than the optical science theory - seat go and do yourself a favour. Read the book Wide-field astrophotography by Robert Reeves published by Willmann Bell publisher and learn about the roll of physical and numerical aperture of lenses (yes, even LF lenses, the guy went through it all) in star trails photography, the background night light etc.
But! I warn you - this astrophotographer he too uses the optical science laws you deny. As a starter for this brain washing experience take a look at his www. robertreeves.com website - you can read some chapter of the given book there.

One thing I would discourage you to do though - asking him for his LF lens photographs to prove the optical science laws he talks about. I think it would be too revelatory and he could lose interest in further communication with you.

[Corran]

Now that you are comfortably seated in your - condescending and ultimately unhelpful - seat, I would ask again for you to elaborate and further this discussion, rather than pushing us to purchase a book.

I am here to learn. I welcome further discussion and perhaps the actual optical science theory / equation / whatever. A link to a relevant article would be helpful. I could find nothing on Reeves' site pertaining to this physical vs. f/number aperture thing, even in the first chapter. Sorry if I've missed it, but please feel free to point it out.

[Corran]

There's also the difference in magnification if one goes from 35mm to 4x5 film. Surely this plays into it as well?

I did a simple experiment - 50mm at f/2.8, and then a 135mm at f/8, so roughly the same aperture size like you say, same exposure time and ISO. Equalized the magnification to simulate using different formats, and got this:

50mm:



135mm:



Sure both have the brighter stars but some of the dimmer stars are gone in the 135mm photo and they are all dimmer in general. Factoring in reciprocity, it would seem the dimmest stars would start to drop off even faster due to not registering on the film before it moved. Again, I am interested in learning and I would like to read more if you have a source of some kind.

[Pfsor]

Again, I am interested in learning and I would like to read more if you have a source of some kind.

Why not trying the book Wide-field astrophotography by R. Reeves I told you about?

[Corran]

You implied all kinds of sources were just a Google search away. Why not provide a link to the specific information/explanation in question? It's really fairly simple. Are you here to contribute meaningful discussion and discourse or just sell books?