dustychow

Gear setup:
Canon EOS 90D + Canon EF 100-400mm F/4.5-5.6L IS II USM Lens or Canon EOS 90D + Canon EF 100-400mm F/4.5-5.6L IS II USM Lens + 1.4TC


I always shoot in Manual mode. I Use Back-Button-Focus exclusively. This doesn't really matter because two years ago I did not know how set up BBF or use it, I still had some the same focus issues. The settings that I use are AI SERVO, S shutter butt half press: Metering start, AF-ON Button: Metering and AF start. Before Each photo shoot I do the following: Clear all Custom Func (CFn), Format SD card-in camera. Clear all camera settings. When I shoot raptors or waterfowl, I often use a Canon 1.4 Teleconverter. I don't use this adapter all the time.


At times I cannot get a focus on a subject, such as a bird either in flight or perched on a post. All I get is a blur through the view finder. Sometimes the camera keeps refocusing but then shifts back to no focus. This is especially true when I might have some image competing elements such as bird in a shrub or tree. birds (raptors) in flight are the toughest its often a problem with focusing on raptors or I cannot get a focus at all on a raptor in flight. Sometimes adjusting the focus ring works but then at time this doesn't work either. Most of the time this is not an issue with the camera+lens as it focuses ok. Aside from this issue I generally get a fairly sharp image. I don't have this problem when I use my macro lens for flowers, plants insects or when using my wide-angle lens for scenery, landscapes, vistas.


What am I doing wrong or what do I need to do to correct this problem?

User ID

Hard to decipher your description but that mention of a shutter button half press jumps out at me as something that ought to be disabled.

Not really sure cuz I cant fully unravel your post, but try disabling that and see what happens. If its not the solution you can just re-enable it.

CHG_CANON Loc: the Windy City

Not being there and not seeing any attached example images, consider a few things:

1, as User ID notes, you should have no focus actions related to the shutter button. With the BBF assigned to a rear button on the body, nothing related to 'focus' should occur with the shutter release button.

2, Check the focus limiter switch on the lens. If your subject is too close and the limiter switch is set to a longer distance, that would explain being unable to focus on a closer subject.

3, Confirm your BBF usage. In addition to having no focus actions on the shutter release button, you need to engage focus with your thumb, holding down the assigned BBF button with your thumb. So the process would by:

i, Raise the camera to your eye.
ii, Press and hold the BBF.
iii, Track the subject (moving) or the static subject, both situations using AI Servo
iv, Release the shutter with your index finger while still holding / pressing the BBF.
v, Remove your index finger from the shutter, when you're done capturing images, either a single frame or short burst.
vi, Release your thumb from the BBF when there is no need to focus on the subject.

4, If applicable, review your touch screen settings and assure your face isn't accidently repositioning the AF location when your have your camera raised in a shooting position.

5, Check your AI Servo settings and see if you linked the AF location to the camera orientation, horizontal vs vertical. See page 565 of the EOS 90D Advanced User Guide.

6, Re-read the AF Settings in the Advanced User Guide, starting on page 123, especially the settings related to the Initial AI Servo AF position and Face+Tracking, Continuous AF, AF-assist beam, and Eye Detection AF.

7, Review your Tracking Sensitivity settings, starting on page 559 of the Advanced User Guide. I prefer customized settings for 'locked' tracking and 'responsiveness'. Read these settings and consider making the camera more likely to remained 'locked' (-1) and more responsive (+1). Consider too making the camera responsive to sudden movements, page 560, with +1 for Acceleration. Finally, encourage the camera to switch points with +1 on the AF switching.

Capn_Dave

You nailed it and saved me a lot of tyhping

Bultaco Loc: Aiken, SC

tcthome Loc: NJ

To add what is the above post. Sometimes you need to turn the Focus Ring on the lens until you have some type of contrast or subject recognition if your camera doesn't see the subject. Then use BBF. The AF-ON button should be pressed while tracking the bird. Also depending on your camera, sometimes you need to take your thumb off the AF-ON button for a split second & press it again to aquire focus. Practice, practice, & practice this some more until it becomes second nature & you don't have to think about it. One other option would be to upgrade to a newer more capable model mirrorless with very sticky-to-your- subject AF. Also more focus points covering the whole EVF that some just use the shutter for focus grab & not the back button AF-ON. Good luck.

SuperflyTNT Loc: Manassas VA

Some of what he described, loosing focus with a busy background, is gonna happen occasionally, but it also sounds like he’s not making use of the focus limiter switch.

dustychow

I need to clarify what I meant to say about BBF - In Custom Functions I set the camera to "Metering start" & "Metering and AF start". I also set the camera to "AI SERVO". When I take a shot I first press the AF-ON button - focuses & composes the image. Next I press the "Shutter Button", as there is no half-press - it takes the shot. I have watched quite a few Youtube vidoes to learn about this technique.

User ID

Thaz the simple basics, so hopefully ALL the many videos were in lockstep on procedure.

CHG_CANON Loc: the Windy City

You don't 'press', you hold the assigned BBF button with the AF mode set to AI SERVO. See process described above. Try it. You'll like it.

dustychow

I should have used the word "hold" instead of "press", but that's what I mean.

CHG_CANON Loc: the Windy City

Great. Thanks for the clarification. So, we seem to have the process correct. With this clarification, have we resolved the issues in usage?

dustychow

UHH Thank-you all - I very much appreciated everyone's feedback & input to my issue of focusing.