Jump to content

Canada's top-tier Telescopes & Accessories
Be as specific as possible when reporting issues and *ALWAYS* include the full version number of the application you are using and your exact *CAMERA MODEL*
NEVER POST YOUR KEY IN ANY PUBLIC FORUM, INCLUDING THE O'TELESCOPE SUPPORT FORUM ::: IF YOU DO YOUR KEY WILL BE DEACTIVATED WITHOUT NOTICE!
  • 0

Cannot focus my Canon 300mm f/2.8 lens


karcoms@gmail.com
 Share

Question

  • Answers 7
  • Created
  • Last Reply

Top Posters For This Question

Popular Days

Top Posters For This Question

7 answers to this question

Recommended Posts

  • 0

Please provide more detail.  Have no clue what you mean. Can't see stars? Can't drive the lens focus motor?

As a general rule of thumb you will only be able to focus on very bright stars, and you need to be close to focus to begin with.  This is because at 300mm everything will be very small and nothing will show otherwise.

Link to comment
Share on other sites

  • 0

It is best to start by attempting Focus on a Distant Daytime object - a Tree or Powerline on the Horizon (or such).  The Brightness and Contrast overcomes the Lack of Focus at start.

If attempting at night, start with the Moon or a Streetlight.

Link to comment
Share on other sites

  • 0

When reporting an issue or asking a question about BYE, please provide both your camera model and the BYE version number, like 3.2.1, that you are using.

BYE should be able to adjust focus on any EF-compatible lens that is mounted on a BYE-connected camera. The lens must be in AF mode. When the lens is in manual focus mode, the lens motor is disconnected from the camera and you must focus manually by means of the lens focus ring.

You adjust the focus from the Frame & Focus Center by means of the chevron buttons that are shown above the active LiveView image. Use of the Chevron buttons is described on page 57 of the BYE User Guide. Those buttons are not displayed unless BYE detects a compatible lens is attached to the camera. You should not install or remove a lens from the camera while BYE is connected to the camera.

Do not expect that the lens will be able to autofocus on night sky targets. They are too dim and too small for the Canon AF circuitry to reliably detect them or focus on them. In that case, you need to put the lens in AF mode while on the Frame & Focus screen and with LiveView active. You should then be able to use the chevron buttons to adjust focus.

Once you are satisified with the focus you need some way to prevent the camera from attempting to autofocus when you take pictures. The default behavior is to autofocus when the shutter button is partially depressed. This also happens when BYE issues a take picture command. You need to prevent the camera from attempting to autofocus when the shutter is depressed. Depending on the camera model you may be able to change a custom setting to move the autofocus from the shutter button to another button on the camera. If not, you need to tape the focus ring in place and switch the lens to MF mode to prevent attempts to re-focus the lens.

On my T5i, for example, changing Custom Function IV (Shutter/AE lock button) from 0:AF/AE lock to 1:AE lock/AF moves the autofocus functionality from the shutter button to the Zoom - button.

I hope this helps.

 

Link to comment
Share on other sites

  • 0
On 3/1/2021 at 10:57 AM, astroman133 said:

When reporting an issue or asking a question about BYE, please provide both your camera model and the BYE version number, like 3.2.1, that you are using.

BYE should be able to adjust focus on any EF-compatible lens that is mounted on a BYE-connected camera. The lens must be in AF mode. When the lens is in manual focus mode, the lens motor is disconnected from the camera and you must focus manually by means of the lens focus ring.

You adjust the focus from the Frame & Focus Center by means of the chevron buttons that are shown above the active LiveView image. Use of the Chevron buttons is described on page 57 of the BYE User Guide. Those buttons are not displayed unless BYE detects a compatible lens is attached to the camera. You should not install or remove a lens from the camera while BYE is connected to the camera.

Do not expect that the lens will be able to autofocus on night sky targets. They are too dim and too small for the Canon AF circuitry to reliably detect them or focus on them. In that case, you need to put the lens in AF mode while on the Frame & Focus screen and with LiveView active. You should then be able to use the chevron buttons to adjust focus.

Once you are satisified with the focus you need some way to prevent the camera from attempting to autofocus when you take pictures. The default behavior is to autofocus when the shutter button is partially depressed. This also happens when BYE issues a take picture command. You need to prevent the camera from attempting to autofocus when the shutter is depressed. Depending on the camera model you may be able to change a custom setting to move the autofocus from the shutter button to another button on the camera. If not, you need to tape the focus ring in place and switch the lens to MF mode to prevent attempts to re-focus the lens.

On my T5i, for example, changing Custom Function IV (Shutter/AE lock button) from 0:AF/AE lock to 1:AE lock/AF moves the autofocus functionality from the shutter button to the Zoom - button.

I hope this helps.

 

I believe the 2 above points depend on the camera and lens.  With my 7D Mark II and my 70-200mm f/2.8 lens I can be in auto or manual focus and I'm able to adjust the focus via BYEOS.  In either mode, taking an image via BYEOS does not change the focus.

On the other hand, if I use my 55-250 f/4-5.6 lens, I can't control the focus in manual focus mode, only in AF mode, as you stated.  However, the focus still does not change if I take an image with BYEOS.

Link to comment
Share on other sites

  • 0

According to the manual for your 70-200 f2.8 lens, you are correct that you can manually turn the focus ring even when the lens is in AF mode, but pressing the shutter button halfway down should cause it to autofocus. The manual says "After autofocusing with the camera in ONE SHOT AF mode, you can adjust the focus by  keeping the shutter button pressed halfway and turning the focusing ring." So, unless the Canon SDK has different logic for your camera, taking a picture with the lens in AF mode should cause the lens to re-focus unless you have mapped the autofocus function to a different button as I mentioned in my previous post.

Thanks!

Link to comment
Share on other sites

  • 0

Maybe the One Shot selection is the key.  I'm in AI Focus mode.

I did test it to make sure, before posting, as it had been a while since I had used a lens with BYEOS.

 

I actually worked with the Canon SDK to debug an issue I was having with camera disconnects, with TheSkyX Pro.  I thought there were different commands in the SDK regarding whether to attempt autofocus when shooting, but I could be misremembering.

Actually, I just found my code, and yes, there is an SDK call, CameraCommand_ShutterButton_Completely_NonAF.  According to the developer I was working with at Software Bisque, that call was implemented in a later version of the SDK.  It could be that Guylain is using that call in BYEOS, as I never had the disconnect issue when using it.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Answer this question...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share


×
×
  • Create New...

Important Information

This site uses cookies to offer your a better browsing experience. You can adjust your cookie settings. By closing this banner, scrolling this page, clicking a link or continuing to browse otherwise, you agree to the use of cookies, our Privacy Policy, and our Terms of Use