How to focus Canon kit lens?

[almcl]

I went down to the dark sky site at the weekend, even though we won't get astro dark here for another two months. I went to see Saturn and to add another Messier object, neither of which ever get above the trees/houses in my back garden.

Just in case, I took the camera and associated paraphernalia along. Unfortunately it was cloudier and windier than forecast so prime focus astrophotography was out but I thought I might have a go at some widefield, using the Canon supplied 18 -55 mm kit lens and piggybacking the camera on the scope. I have had reasonable results with this technique in the past although haven't tried it with a DSLR before.

All went well and I spent much of the nautical twilight gazing at Saturn's rings and then at M80 which was quite low in the haze layer.

Then moved on to the widefield. Came up against a problem: how do you focus the late model Canons? Normally I have no difficulty with this at telescope prime focus, using live view x10 and connected to a 10" tablet screen, stars are easy to see and focus on but with the 18 - 55mm lens, even with the ISO wacked up to 12800, there was nothing to see to focus on. Using the auto focus didn't quite get things in focus, either.

So any other Canon 700 (Rebel T5i) users care to share their techniques?

Widefield view (Ophiuchus is roughly centre)

Blow up of out of focus stars

[cathouse42]

Canon kit lenses can focus past infinity.  (found this article about this issue, http://www.bhphotovideo.com/explora/photography/features/who-killed-infinity-focus)

I tend to focus with all settings max on a bright star or planet (Jupiter?)and focus manually using live view and it works most of the time.

Never really had a problem with manual focus on wide field this way yet. I also dumped my kit lens though, it was pure plastic rubbish. Even with it I could nail infinity focus.

You could try on a distant lamp?

That also looks like coma in your images. Try stopping down the lens aperture?

http://randombio.com/astrophotography-without-a-telescope.html

[Tinker1947]

I would take note of where the focus point on the lens rings, then depending on the speed of the lens drop it down a bit the get some DOF, my 100mm F2 i use at 2.8  or 3.5 this gives sharp stars........i  focus on a bright star then drop the f-stop never tried with the kit lens though..... 

[cathouse42]

Do vintage lenses focus past infinity on the focus ring? I'm guessing they hard stop at infinity, Seems to be a modern thing, focusing past infinity.

Would be nice if they still had a HARD STOP at infinity, and a means to focus past if need be, but with a reassuring CLUNK on the infinity mark.

[almcl]

Thanks for the thoughts both - silly of me not to think of stopping down!

There was a distinct lack of anything to focus on - even Vega refused to show up and of course the dark sky site has (almost) no artificial lights visible - apart from passing cars...

Not sure about marking the focus ring - wouldn't it be in a different place next time if the electronic auto focus had been in operation?

[hazegood]

Do vintage lenses focus past infinity on the focus ring? I'm guessing they hard stop at infinity, Seems to be a modern thing, focusing past infinity.

Would be nice if they still had a HARD STOP at infinity, and a means to focus past if need be, but with a reassuring CLUNK on the infinity mark.

My Vintage Zeiss Jenna 135mm hard stops at its infinity mark, but some times needs a vry sligh nudge backwards to focus,

Focusing past infinity on modern lenses is to do with how the auto focus system works, when hunting for foucs it needs to go past infinity then back again

[hazegood]

Thanks for the thoughts both - silly of me not to think of stopping down!

There was a distinct lack of anything to focus on - even Vega refused to show up and of course the dark sky site has (almost) no artificial lights visible - apart from passing cars...

Not sure about marking the focus ring - wouldn't it be in a different place next time if the electronic auto focus had been in operation?

Thanks for the thoughts both - silly of me not to think of stopping down!

There was a distinct lack of anything to focus on - even Vega refused to show up and of course the dark sky site has (almost) no artificial lights visible - apart from passing cars...

Not sure about marking the focus ring - wouldn't it be in a different place next time if the electronic auto focus had been in operation?

no you use a whit or other colour you can see in the darkish light marker pen and when you know the lens is at focus draw a line over the focus ring and onto the lens body, then no matter how much autofocus you use with the lens for other things if you switch to MF, and line the lines you painted back up, the lens will be focused the same

[almcl]

no you use a white marker pen and when the lens is at focus, draw a line over the focus ring and the lens body, then no matter how much autofocus you use, if you switch to MF and line the lines up, the lens will be focused the same

That's really useful to know, many thanks. I'll have to wait till the moon's about and have a play - never thought I'd be saying that!

[happy-kat]

My three different vintage lens focus past infinity

[wxsatuser]

Blow up of out of focus stars

out of foucs stars.jpg

That is sagittal coma flare.

This happens when sagittal astigmatism is combined with coma, often refered to as the flying bird.

Your not alone with this, even expensive lenses are not immune.

[Knight of Clear Skies]

The kit lens can be a bit of a pain to focus if there isn't a planet visible. It will only show the brightest stars in liveview even with the aperture wide open and ISO at maximum, which may be in a different part of the sky to your target. To focus I open the aperture right up then stop down to f5.6 for imaging, as this reduces coma. I also use a bit of blue-tac on the focus ring to stop it slipping out of focus, there isn't enough friction in the mechanism. My vintage lenses are much better behaved in this respect, manual focus is a bit of an afterthought with many modern ones.

[cathouse42]

Jupiter should do the trick

[Alien 13]

I have the 650D and IS version of the 18-55mm and have never had a problem seeing stars on liveview (provided the focus is close), as said for setting up use a high ISO, shutter speed to 20 seconds or so and zoom in to x10 but most importantly use the camera screen not a laptop etc.

Alan

[Skipper Billy]

I have only one vintage lens - a Super Takumar 200mm - its a cracking lens and it hard stops just past infinity - about 1mm on the focus ring.  I quite like this as if it stopped dead on infinity I would always be wondering if it would be sharper if it moved just that little bit more !!!  The only lens I have ever owned that hard stopped at dead on infinity was a Hasselbald that cost more than my entire imaging rig !!!

This also begs the question 'what is beyond infinity called ' ???     

[cathouse42]

I have only one vintage lens - a Super Takumar 200mm - its a cracking lens and it hard stops just past infinity - about 1mm on the focus ring.  I quite like this as if it stopped dead on infinity I would always be wondering if it would be sharper if it moved just that little bit more !!!  The only lens I have ever owned that hard stopped at dead on infinity was a Hasselbald that cost more than my entire imaging rig !!!

This also begs the question 'what is beyond infinity called ' ???     

I think it is called Buzz Lightyear

Anyway, a good lens in those days was one that had perfect infinity at the hard stop, however, a compromise would be some kind of tactile feedback (a little bump perhaps) and then the ability to focus past that bump.

[happy-kat]

There is a trick you can use with the kit lens to ensure that there is no focus slip.

Right now I can't exactly recall the steps but it is along the lines of set focus up using manual then switch to autofocus. On the camera you will have already set up focus lock, so it means that when in autofocus the camera will not hunt and will hold what ever position you have set the focus at.

[almcl]

Thanks for that happy-kat, I haven't investigated focus lock yet and can't find it in the 387 page EOS book - do Canon refer to it by another name?

I did try out focussing on Venus last night, made the yellow marks on barrel and focus ring but unfortunately after auto or switch off and switch on they were no where near each other at the focus point so that idea bit the dust, unfortunately.

[Mark62]

That's really useful to know, many thanks. I'll have to wait till the moon's about and have a play - never thought I'd be saying that!

You don't have to wait for the moon. You can do it through the day just auto focus on a distant object something about 1/4 of a mile and mark ur lens

Like so the dots are just a reference for my self as I've marked mine at 100 200 and 300mm

Mark

[Mark62]

Ps use in MF when using this method [emoji106]

[almcl]

Ps use in MF when using this method [emoji106]

Mark

Unfortunately, Mark, that didn't work and, yes, it was in manual mode when the marks were made...

My lens is an EFS, whereas I see the one in your image is an EF. Not sure if that is the explanation but it might have a bearing.

[Mark62]

Unfortunately, Mark, that didn't work and, yes, it was in manual mode when the marks were made...

My lens is an EFS, whereas I see the one in your image is an EF. Not sure if that is the explanation but it might have a bearing.

You set it up in auto focus put the marks on the focus ring and lens. Then when u come to use it you switch to MF. Set up ur Marks and it won't move off ur preset focus

Mark

[happy-kat]

Thanks for that happy-kat, I haven't investigated focus lock yet and can't find it in the 387 page EOS book - do Canon refer to it by another name?

Rather a chocolate T pot as I can't find the thread where I read about it, which is useless for me too as I was going to look into using it next time I did anything like that with my camera.

[happy-kat]

I have back button focus setup on my camera and got me thinking that this holds focus until I press the back button again, so using manual focus to set it and then switching the lens to auto focus the focus in theory should not alter until I chose to change it with the back button. This did work like that when I did a timelapse the focus did not change and I was using a remote trigger.

[RichM63]

Start with page 61 and work forward.

I'm with Happy and use 'back button' focus. Custom functions Cfn4 for AF but tend to use manual at night as the sensors are not generally good enough to use AF + I have  rather demanding manual lenses in the bag. 

As per others marking the real infinity setting even helps during long range day time shooting.

[Alien 13]

I have just looked through my manual and cant find any mention of "back button focus" is this something only available with Magic Lantern firmware.

Alan