first get into Astro photography you may just want to use your kit lens or you
might want to buy a new lens with a much bigger aperture but then you look at the
price and they seem to get exponentially more costly with these wider apertures
so I'm going to look at the practical differences between these different
apertures as the price varies so much an F 2.8 zoom is typically double the price
of an f4 zoom and if you're looking at prime lenses and F 1.4 prime lens is
pretty much double the price of an F 1.8 prime lens now the difference between
the prime lens and a zoom is that a zoom has a range of focal lengths and it can
zoom in or it can go to a telephoto length whereas a prime lens has a fixed
focal length and it stays there it doesn't zoom in or out at all now if you
look online at all and do any kind of research on Astro photography everyone
says you need an F 2.8 or faster lens so that's F 2.8 or a lower F number now
even though the difference between F 4 and F 1.4 is three stops of light this
is massive when you're shooting at night and can make the difference between a
good shot and a bad shot so I went out last night and shot a series of photos
from f/4 right through to F 1.4 this first sequence shows you how much
brighter three stops actually is in real terms I've kept the ISO and shutter
speed exactly the same between all of these shots you can see the F 1.4 lens
let in so much more light and so this is why it's much better for
astrophotography so even though it's only three stops this is eight times the
amount of light that it'll actually let in so one stop is twice the amount of
light two stops is four times the amount of light and three stops is eight times
the amount of light with astrophotography you have the five
hundred rule for full-frame cameras and the 300 rule for crop censored
cameras so you're limited to how long the exposure is when shooting from a
fixed tripod so the only thing that you can play with really is your eye so if
you're not sure what the 500 rule is make sure to click on the eye in the
corner or the link in the description where I have another video on this I use
bright monitoring to frame up my shot I set the shutter speed for the given
focal length today I'm at 24 millimeters and I'm
going to be cautious so I'll keep my shutter speed to 15 seconds I then open
the aperture as wide as possible I set my ISO and then I start taking
photographs with these lenses with bigger apertures I can open up the
aperture and decrease the application of the signal from the sensor all to us
mere mortals lower the ISO this in turn lowers the amount of noise you will get
in your shot so let's say for example I'm shooting with a 24 millimeter lens
my lens has a maximum aperture of f/4 and I've chosen a conservative shutter
speed of 15 seconds with the conditions I had at a portal 3 location I had to
push the ISO up to 12,000 800 to get a good exposure and with ISOs at that
level it does come out a bit noisy but I was quite surprised with how good the
image actually looked now if I switch this out with a faster lens with an
aperture of f-14 with a 15 second shutter speed again I can bring the ISO
down to 1600 which is a massive difference and if you don't know what
dropping the ISO does it basically reduces the amount of noise in your
images because that signal doesn't have to be amplified as much this next set of
exposures was taken once the Milkyway had risen looking at the images like
this scaled down it is hard to tell the difference but when you zoom in the
image taken at one point four is less noisy especially in the foreground if I
crop in on the f4 and the F 1.4 images you could see the difference in the
noise patterns and when edited the one with the lower ISO can be pushed
around a lot more these images have been taken with the a 73 which is really good
at high ISOs but if you use a different brand it'd be worth going out and
checking it before deciding on what to do so if you are using a lens that has a
maximum aperture of f/4 this may be the reason why you're getting good Astro
shots but not great Astro shots when you use the kit lens or a lens with an
aperture of f/4 or smaller there is a lot less light being let into the camera
and this in turns means a lower quality image when you're taking photographs
with a full-frame camera and say a 14 millimeter lens and you're not going to
be blowing your images up to poster size you can shoot with anything up to 30
seconds so you could probably get away with an f/4 lens but with a 35
millimeter or a 50 millimeter lens it's the difference between getting a usable
shot and a non usable shot and this is when the wide apertures really do help
in saying that if you are shooting with a 14 millimeter lens if you get a lens
with a much wider aperture again this will let loads more light in and you'll
be able to drop your ISO even more and then you'll be able to get much cleaner
images now if you don't want to spend all of that money on really wide
aperture lenses because they are so expensive there are two ways around this
and this is by stacking your shots or by using a tracker these both enabled you
to get much better images with kit lenses and with lenses with smaller
apertures than these fast lenses that do cost all of that money and stacking is
the cheapest way if you want to learn more about that click on the eye in the
corner or the link in the description to another of my tutorials if you can only
afford the kit lens you can still go out and get some great photos of the stars
but I would suggest stacking your photos but to take your photos to another level
it's definitely worth saving up and getting a really wide aperture lens and
with companies such as samyang and Sigma you really don't have to spend that much
to get a good fast wide-angle lens for your camera
for what lenses to buy if you're on a budget get something like this samyang
14 millimeter F 2.8 or if you're shooting with a crop sensor camera get
the samyang 12 millimeter f/2 they are both great for astrophotography and come
in at quite a good affordable price if you have a little bit more to spend you
could try some of the lenses from Venus optics they do some great lenses but are
a little bit more expensive and if you have plenty to spend get the pro line of
prime lenses from the brand of cameras you normally shoot with for me this
would be the sony g master lenses and the 24 millimeter f one point four is a
fantastic lens for astrophotography there are tons of lenses out there so
just do the research on them and then you'll definitely find one that will
suit your budget in camera like I said if you can't afford any other lenses use
your kit lens I take a series of shots and then stack them afterwards on your