55-300mm f/4.5-6.3 PLM infinity focusing

eric3929 · 04-06-2020, 08:55 AM

Hey all, I'm wondering if anyone knows the 'maximum' focal distance as this lens approaches focusing to infinity? I took it out for some astro shots the other night (I know, it's slow but in the telephoto category it's what I have). I'm not used to the focus by wire set up. With some of my other lenses, like HD 15mm f/4 I can easily focus to infinity in the dark, no problem. Here I've got no hard stops, no numbers, nothing. I'm thinking I may set up a bright flashlight near a tree or something, walk away, focus on that, and then aim at the sky. But, I'm wondering how far away I'd need to walk? 50 feet? 100 feet? If anyone has some experience using this lens (or any focus by wire lens) at night let me know how you're managing. Thanks!

bertwert · 04-06-2020, 08:58 AM

Originally posted by eric3929

Hey all, I'm wondering if anyone knows the 'maximum' focal distance as this lens approaches focusing to infinity? I took it out for some astro shots the other night (I know, it's slow but in the telephoto category it's what I have). I'm not used to the focus by wire set up. With some of my other lenses, like HD 15mm f/4 I can easily focus to infinity in the dark, no problem. Here I've got no hard stops, no numbers, nothing. I'm thinking I may set up a bright flashlight near a tree or something, walk away, focus on that, and then aim at the sky. But, I'm wondering how far away I'd need to walk? 50 feet? 100 feet? If anyone has some experience using this lens (or any focus by wire lens) at night let me know how you're managing. Thanks!

Now, I've never used any focus-by-wire lenses. But when the camera is off, the focus will not change when turning the lens - right?

Could you focus it to infinity during the day when you can see, then leave the camera off until nightime with it switched to MF or use AF with back button, and not refocus.

Just a shot in the dark (ha), but in theory this should work...

eric3929 · 04-06-2020, 09:03 AM

Originally posted by bertwert

Now, I've never used any focus-by-wire lenses. But when the camera is off, the focus will not change when turning the lens - right?

Could you focus it to infinity during the day when you can see, then leave the camera off until nightime with it switched to MF or use AF with back button, and not refocus.

Just a shot in the dark (ha), but in theory this should work...

This was my plan as well - although when I arrived at the place I intended to shoot it was way out of focus. I'm not sure if it is just really easy to spin by accident, of if it doesn't always come back to life at the same focal point? But if this technique has been working for people with this lens I'd like to hear that!

bertwert · 04-06-2020, 09:06 AM

Originally posted by eric3929

I'm not sure if it is just really easy to spin by accident, of if it doesn't always come back to life at the same focal point?

Again, I don't know what I'm talking about.... but have you tried this method when leaving it in AF mode, but using back-button focus so you don't refocus with the shutter button. This way you shouldn't have to worry about accidentally spinning it. I don't know however if the focus moves over time. With non-focus-by-wire lenses, it's easy as you just tape the lens in focus position or mark it in some way...

**microlight** · 04-06-2020, 10:08 AM - **2 Likes**

What about using LiveView and magnification to focus?

Chris_K · 04-06-2020, 10:36 AM

The focus-by-wire in this lens doesn't work when the camera is off (just checked it) so accidental turning the focus ring when the camera if off shouldn't be a problem...

**SteveinSLC** · 04-06-2020, 12:32 PM - **1 Like**

For astro, you shouldn't be going off of numbers or stops with any lens.
Switch to manual focus and Live View. Find a bright star, magnify and focus until the star is as small and sharp as possible. If you're concerned about bumping the focusing ring, use gaffer tape to tape it in place.

eric3929 · 04-06-2020, 02:02 PM

Originally posted by Chris_K

The focus-by-wire in this lens doesn't work when the camera is off (just checked it) so accidental turning the focus ring when the camera if off shouldn't be a problem...

Chris (and Bert), you're right. I tried this also just now and focus will not change while the camera is off. I was using an OGPS1 unit, and perhaps during calibration I hit the zoom ring. I'll try this again next time I have clear skies and time to get out.

As far as LiveView - I've tried this technique at night with mixed results. I sometimes come home to find decent images and other times come home to find they all missed focus but a small amount. That's why I'm quite happy with the hard stop on my 15mm. I've tested it in daylight a few times, and the hard stop at infinite is a really good focus. I have other lenses that will focus a little past infinite - so I don't use that technique with all of them.

Thanks everyone for your input. Astro is a genre I have only tried a handful of times. It's fun - but it seems like you never really know how good your images will be until the back at a computer. So, I just want to be as prepared as possible while in the field to minimize user error.

Bertrand3000 · 04-07-2020, 03:15 AM - **1 Like**

Hard stop is unfortunately not enough to garantee an easy infinite focus. My Tamron 70-300 has a hard stop beyond infinity, all my night shots were blurred.

**ThorSanchez** · 04-07-2020, 04:27 AM

You could try a Bahtinov Mask. I've 3D printed one for the 55-300PLM, but haven't tried it out yet. You put it on the front of the lens like a filter. The mask creates a diffraction pattern that has a particular look when you're exactly at infinity focus. Then you take it off and shoot away.

I forget that I have the thing, I need to take it out tonight to try it out.

eric3929 · 04-07-2020, 06:50 AM - **1 Like**

Originally posted by ThorSanchez

You could try a Bahtinov Mask. I've 3D printed one for the 55-300PLM, but haven't tried it out yet. You put it on the front of the lens like a filter. The mask creates a diffraction pattern that has a particular look when you're exactly at infinity focus. Then you take it off and shoot away.

I forget that I have the thing, I need to take it out tonight to try it out.

I like this idea, let us know if your printed mask works well. Unfortunately I don't have a 3D printer. Or any printer for that matter (as I'm currently working from home).

**rogerstg** · 04-08-2020, 05:07 AM

Originally posted by eric3929

Unfortunately I don't have a 3D printer.

Do you have internet access?

Amazon, B&H

**ThorSanchez** · 04-08-2020, 05:50 AM

Originally posted by rogerstg

Do you have internet access?

Amazon, B&H

The link I provided showed a Bahitnov mask made out of cardboard or construction paper with an exacto knife.

04-06-2020, 08:55 AM	#1
eric3929 Senior Member Join Date: Aug 2019 Posts: 106	55-300mm f/4.5-6.3 PLM infinity focusing Hey all, I'm wondering if anyone knows the 'maximum' focal distance as this lens approaches focusing to infinity? I took it out for some astro shots the other night (I know, it's slow but in the telephoto category it's what I have). I'm not used to the focus by wire set up. With some of my other lenses, like HD 15mm f/4 I can easily focus to infinity in the dark, no problem. Here I've got no hard stops, no numbers, nothing. I'm thinking I may set up a bright flashlight near a tree or something, walk away, focus on that, and then aim at the sky. But, I'm wondering how far away I'd need to walk? 50 feet? 100 feet? If anyone has some experience using this lens (or any focus by wire lens) at night let me know how you're managing. Thanks!

04-06-2020, 09:03 AM	#3
eric3929 Senior Member Join Date: Aug 2019 Posts: 106 Original Poster	pre focus Originally posted by bertwert Now, I've never used any focus-by-wire lenses. But when the camera is off, the focus will not change when turning the lens - right? Could you focus it to infinity during the day when you can see, then leave the camera off until nightime with it switched to MF or use AF with back button, and not refocus. Just a shot in the dark (ha), but in theory this should work... This was my plan as well - although when I arrived at the place I intended to shoot it was way out of focus. I'm not sure if it is just really easy to spin by accident, of if it doesn't always come back to life at the same focal point? But if this technique has been working for people with this lens I'd like to hear that!

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04-06-2020, 08:58 AM	#2
bertwert Veteran Member Join Date: Jun 2015 Location: Golden, BC Posts: 15,173	Originally posted by eric3929 Hey all, I'm wondering if anyone knows the 'maximum' focal distance as this lens approaches focusing to infinity? I took it out for some astro shots the other night (I know, it's slow but in the telephoto category it's what I have). I'm not used to the focus by wire set up. With some of my other lenses, like HD 15mm f/4 I can easily focus to infinity in the dark, no problem. Here I've got no hard stops, no numbers, nothing. I'm thinking I may set up a bright flashlight near a tree or something, walk away, focus on that, and then aim at the sky. But, I'm wondering how far away I'd need to walk? 50 feet? 100 feet? If anyone has some experience using this lens (or any focus by wire lens) at night let me know how you're managing. Thanks! Now, I've never used any focus-by-wire lenses. But when the camera is off, the focus will not change when turning the lens - right? Could you focus it to infinity during the day when you can see, then leave the camera off until nightime with it switched to MF or use AF with back button, and not refocus. Just a shot in the dark (ha), but in theory this should work...

04-06-2020, 09:06 AM	#4
bertwert Veteran Member Join Date: Jun 2015 Location: Golden, BC Posts: 15,173	Originally posted by eric3929 I'm not sure if it is just really easy to spin by accident, of if it doesn't always come back to life at the same focal point? Again, I don't know what I'm talking about.... but have you tried this method when leaving it in AF mode, but using back-button focus so you don't refocus with the shutter button. This way you shouldn't have to worry about accidentally spinning it. I don't know however if the focus moves over time. With non-focus-by-wire lenses, it's easy as you just tape the lens in focus position or mark it in some way...

04-06-2020, 10:08 AM - 2 Likes	#5
microlight Site Supporter Join Date: Sep 2011 Location: Hampshire, UK Posts: 2,129	What about using LiveView and magnification to focus?

04-06-2020, 10:36 AM	#6
Chris_K Pentaxian Join Date: Sep 2018 Location: Poland Photos: Gallery \| Albums Posts: 1,800	The focus-by-wire in this lens doesn't work when the camera is off (just checked it) so accidental turning the focus ring when the camera if off shouldn't be a problem...

04-06-2020, 12:32 PM - 1 Like	#7
SteveinSLC Site Supporter Join Date: Mar 2017 Photos: Gallery \| Albums Posts: 568	For astro, you shouldn't be going off of numbers or stops with any lens. Switch to manual focus and Live View. Find a bright star, magnify and focus until the star is as small and sharp as possible. If you're concerned about bumping the focusing ring, use gaffer tape to tape it in place.

04-06-2020, 02:02 PM	#8
eric3929 Senior Member Join Date: Aug 2019 Posts: 106 Original Poster	Originally posted by Chris_K The focus-by-wire in this lens doesn't work when the camera is off (just checked it) so accidental turning the focus ring when the camera if off shouldn't be a problem... Chris (and Bert), you're right. I tried this also just now and focus will not change while the camera is off. I was using an OGPS1 unit, and perhaps during calibration I hit the zoom ring. I'll try this again next time I have clear skies and time to get out. As far as LiveView - I've tried this technique at night with mixed results. I sometimes come home to find decent images and other times come home to find they all missed focus but a small amount. That's why I'm quite happy with the hard stop on my 15mm. I've tested it in daylight a few times, and the hard stop at infinite is a really good focus. I have other lenses that will focus a little past infinite - so I don't use that technique with all of them. Thanks everyone for your input. Astro is a genre I have only tried a handful of times. It's fun - but it seems like you never really know how good your images will be until the back at a computer. So, I just want to be as prepared as possible while in the field to minimize user error.

04-07-2020, 03:15 AM - 1 Like	#9
Bertrand3000 Veteran Member Join Date: Feb 2019 Posts: 2,009	Hard stop is unfortunately not enough to garantee an easy infinite focus. My Tamron 70-300 has a hard stop beyond infinity, all my night shots were blurred.

04-07-2020, 04:27 AM	#10
ThorSanchez Site Supporter Join Date: Dec 2012 Photos: Gallery \| Albums Posts: 2,806	You could try a Bahtinov Mask. I've 3D printed one for the 55-300PLM, but haven't tried it out yet. You put it on the front of the lens like a filter. The mask creates a diffraction pattern that has a particular look when you're exactly at infinity focus. Then you take it off and shoot away. I forget that I have the thing, I need to take it out tonight to try it out.

04-07-2020, 06:50 AM - 1 Like	#11
eric3929 Senior Member Join Date: Aug 2019 Posts: 106 Original Poster	Originally posted by ThorSanchez You could try a Bahtinov Mask. I've 3D printed one for the 55-300PLM, but haven't tried it out yet. You put it on the front of the lens like a filter. The mask creates a diffraction pattern that has a particular look when you're exactly at infinity focus. Then you take it off and shoot away. I forget that I have the thing, I need to take it out tonight to try it out. I like this idea, let us know if your printed mask works well. Unfortunately I don't have a 3D printer. Or any printer for that matter (as I'm currently working from home).

04-08-2020, 05:07 AM	#12
rogerstg Loyal Site Supporter Join Date: Oct 2007 Location: Rhode Island Photos: Albums Posts: 1,168	Originally posted by eric3929 Unfortunately I don't have a 3D printer. Do you have internet access? Amazon, B&H

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04-08-2020, 05:50 AM	#13
ThorSanchez Site Supporter Join Date: Dec 2012 Photos: Gallery \| Albums Posts: 2,806	Originally posted by rogerstg Do you have internet access? Amazon, B&H The link I provided showed a Bahitnov mask made out of cardboard or construction paper with an exacto knife.