Lens Shopping Again

[ElizaMM]

Can someone please give me an opinion on lenses -- I would like a lens with a little faster aperture than F4 for the night sky. I am looking at the Canon EF-S 24MM F2.8 STM lens. Would this be a big improvement over my Canon 24-105 at 24mm & F4, on a 7D? I don't need IS, as I will use it only with a tripod. The price seems to go up exponentially, the shorter the lens and the larger the aperture. Since I'm an amateur, cost drives the choice.

 

[qmr55]

If you're using a tripod, then you don't really need a faster lens for "night sky". Open your lens up to f7-f9 and bump the shutter speed up.

 

[ElizaMM]

When using an aperture of f7, or smaller, I have to use longer exposures and end up with star trails. I am thinking more of milky way photos and the shortest exposure possible to capture as little movement as possible, which is why I think a wider angle lens might be better. Increasing the ISO causes graininess.

 

[kundalini]

At f/2.8, your depth-of-field is extremely shallow. How does that help you focus on objects millions and millions and millions of miles away?

 

[sw_]

At f/2.8, your depth-of-field is extremely shallow. How does that help you focus on objects millions and millions and millions of miles away?

Infinity focus

OP: have you looked at 3rd party such as rokinon? Heck even a 35mm prime is fantastic, to be fair I'm not a canon shooter so I don't know their primes.

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[ElizaMM]

Thanks for the lens suggestion, I will see what Henry's has in a 35mm prime. Re the shallow depth of field at f/2.8, can you point me to examples taken with smaller apertures? The sites that I have visited re this question have advised the use of the shortest focal length possible and the largest aperture possible - f/2.8 or lower - for trying to capture the center of the Milky Way. I was able to capture it in August of last year at f/5, 24mm, 20s, and it's okay when viewed at 4" x 6", but looks amateurish when enlarged. I would like to have a larger "hangable" photo, that looks a little closer to professional.

 

[benhasajeep]

You don't have to get an AF lens unless you want to use it for general photography as well. Infinity focus is all you need for galaxy shots. You can use Nikon or screw mount lenses with adapters on Canon. But you need a special adapter that increases focal length to use old FD lenses. There are faster lenses than f/2.8 available for fairly low cost compared to new fast L glass.

 

[petrochemist]

For night sky (star field) shots I often want something significantly wider than 24mm.

 

[petrochemist]

At f/2.8, your depth-of-field is extremely shallow. How does that help you focus on objects millions and millions and millions of miles away?

At f/1.2 & focused on stars the DOF is many billions of miles even with longer focal length lenses.
Getting the focus spot on does become much more critical with fast lenses, but if you can manage it then the only advantage of stopping down is to reduce aberrations.

 

[Designer]

I suggest that you search the forums on here for threads that discuss shooting the Milky Way. Lots of them.

Also; I found this:

How to Photograph the Milky Way the Easy Way

 

[Destin]

Since nobody else has actually suggested a lens, check out the rokinon 14mm 2.8. It's manual focus only but lots of people use it for astrophotography with great results.

Also, there is lots of bad information floating around in here. You definitely want a fast lens to shoot the Milky Way and you'll want to be wide open. DOF is a non issue unless you want the foreground also to be I focus because when focused at infinity, even wide open, your DOF is massive.

 

[qmr55]

Since nobody else has actually suggested a lens, check out the rokinon 14mm 2.8. It's manual focus only but lots of people use it for astrophotography with great results.

Also, there is lots of bad information floating around in here. You definitely want a fast lens to shoot the Milky Way and you'll want to be wide open. DOF is a non issue unless you want the foreground also to be I focus because when focused at infinity, even wide open, your DOF is massive.

To be fair, when I responded Milky Way was not mentioned yet. I took "night sky" as meaning outside at night. Aka long exposures.

 

[petrochemist]

To be fair, when I responded Milky Way was not mentioned yet. I took "night sky" as meaning outside at night. Aka long exposures.

IMO 'Night sky' implies stars. Which means the same conditions as Milky way shots unless star trials are wanted.
Just outside at night would not have included the word sky.

With a tracking mount long exposures of stars are possible, but this sis normally only used for deep sky objects which are dim enough to need long exposures at the widest available aperture...