Why won't my Canon 400 mm prime lens focus?

[AnneEM]

Hello. I have a Canon 400 mm prime lens on a Canon Rebel camera. I am a wildlife photographer, so my camera has been used in some extreme temperatures. I have noticed lately that my camera does not always want to focus on wildlife. For instance, I was trying to take pictures of owls and while they showed up focused on the viewfinder and the auto focus was going off, they ended up not focused on my actual camera. This has been a problem for 3 months now. Sometimes it will focus, but half of the time it does not. I have never had this issue before. I use the P setting and my 400 mm lens a large majority of the time. I had my camera looked at very briefly at a shop and they found nothing obviously wrong with it. I'm not sure if its a problem with my lens or camera. I want to say it's my lens but I'm not sure because I only use the 400 since I photograph wildlife. Does this problem sound familiar to anyone?

[ebiggs1]

diverhank,

It is possible even for and old has been like me to get reasonably sharp photos with less than perfect technique.  This is hand held with the big Siggy at 600mm.  Av fixed at wide open, SS was 1/640 selected by the Mk IV and of course the ISO of 400.

 

A more reasonable SS might be in the 1/1000 range and higher for this combo.

A trip to the Omaha zoo with just snapshots in mind, grandkids were with me, this was the Mk IV with my 70-200 @ 200mm.

SS was selected of 1/250 and again ISO of 400.  To get a sharp photo with 200mm is going to be a lot easier than with 600mm or even 400mm.   That is why I suspect her crane is much better.

[ebiggs1]

diverhank,

BTW, both of those are pretty aggressive crops.  That possibility is one reason I don't use or like Auto ISO.  I want to know where it is.

[Waddizzle]

Food for thought.  When I use Auto ISO, I set an upper ISO limit in the menus.  No need to set it manually.  My preference is to keep an eyeball on the SS and let camera figure out ISO, especially under widely varying light conditions. 

One quirk with letting the camera determine SS or ISO, though, it makes exposure compensation misbehave.

[TTMartin]

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@AnneEM wrote:

Thank you everyone for your contributions. And sorry for the delay in response. I just now had time to get out and try out the different settings on my camera.

Unfortunately, the Tv mode did not work well on my camera. In fact, I did a little experiment. I tried the same exact settings with my lens on two different cameras, both of which are Canon Rebals. ( Mine is a t1i and my fiance's is a t3i). One person took pictures of the same subjects with the same shutter speed on Tv mode. We picked a shutter speed of 1/2500 and an auto ISO. Everything else was the same other than the camera body change. We even use a flat platform to act as a tripod to minimize shaking.

First, I'll present you a photo of my attempt to take a picture of a bird on the settings suggested. Link here: GREG on Tv mode

The shutter speed was 1/500, and the bird was not moving. I usually take images of birds when they are relatively stationary. I don't take flying images often. The ISO was auto and my camera chose 100. This was at 400 mm.

This image frustrated me, so that's when I started the experiment. Here are the results:

Tree on t3i

Tree on t1i

If you zoom in, you'll notice that the tree is sharper on my fiance's camera (t3i) than mine. My camera chose an ISO of 1000 while his chose an ISO of 800.

In the past, my camera has chosen decent shutter speeds on its own with P mode. For instance, this picture of sandhill cranes came out well and it was on P. (Link here: Sandhill Crane Family) The shutter speed for that image was 1/2000 with an ISO of 800. So it does seem fishy that P has not worked for me at all recently when it used to be fine.

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Take your camera and lens, and stop it down to f/32 and take a picture of clear blue sky. It looks to me like your sensor needs cleaning. 

[diverhank]

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@ebiggs1 wrote:

diverhank,

BTW, both of those are pretty aggressive crops.  That possibility is one reason I don't use or like Auto ISO.  I want to know where it is.

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Thanks for the explanation.  I guess I don't disagree with anything you said.  

Even though I'm no pro by any standards, most of the time I shoot in full manual (Av, Tv, ISO) except when shooting birds in flight where I use M with Auto ISO.  My favorite BIF action is to track and take pictures of  an osprey loitering 200ft above a lake, ocassionally swooping down into the water and emerging with a fish.  The whole sequence takes about 2 or 3 seconds flat and the light conditions change so dramatically, a fixed ISO would spell disaster (I had many ruined shots to show for).  An Osprey sequence like that only comes like twice a year so missing a shot is always cause for getting drunk to get rid of the sorrow :).  Like Waddizzle, I limit the upper ISO to something I can live it and auto ISO works really well, especially my 7D Mark II allows me to do exposure compensation in M mode so I can compensate for the darker bird.

[ebiggs1]

Whatever works.

[AnneEM]

Thank you again, everyone for the constructive feedback! I am happy to say that I have in fact found the solution to the focusing issue.

Basically, I was not convinced that it was user error. (Sorry) Simply due to the fact that I have shot handheld with a relatively slow SS on non-ideal weather days before and my pictures have been fine. Yes, I have shot handheld with a SS of 1/400 or 1/500 with my 400 mm fixed lens before and my pictures were fine up until recently. For example, I have three sharp images below with handheld technique and low SS.

GREG with 1/500 SS

SNEG with SS 1/500

PUGA with SS 1/500

This is why I had a difficult time understanding that motion was the issue with the camera. Yes, it very well could have been a factor. (I will try faster SS in the future!) But I still had a hard time understanding why it would blur my photos this consistently after being able to take perfectly fine photos for 3 plus years. So I took it into a Canon Certified Repair Shop. It was looked at by staff in a backroom for 25 minutes. They came back and told me that my camera was back focusing and that something in the camera was bumped out of place, which is understandable because I was using my camera intensively in Florida. When testing it, they used their own lens so it was not my lens at fault, but my camera body itself. So now, it is getting repaired.

Thank you again for the help.

[TTMartin]

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@AnneEM wrote:

Thank you again, everyone for the constructive feedback! I am happy to say that I have in fact found the solution to the focusing issue.

Basically, I was not convinced that it was user error. (Sorry) Simply due to the fact that I have shot handheld with a relatively slow SS on non-ideal weather days before and my pictures have been fine. Yes, I have shot handheld with a SS of 1/400 or 1/500 with my 400 mm fixed lens before and my pictures were fine up until recently. For example, I have three sharp images below with handheld technique and low SS.

GREG with 1/500 SS

SNEG with SS 1/500

PUGA with SS 1/500

This is why I had a difficult time understanding that motion was the issue with the camera. Yes, it very well could have been a factor. (I will try faster SS in the future!) But I still had a hard time understanding why it would blur my photos this consistently after being able to take perfectly fine photos for 3 plus years. So I took it into a Canon Certified Repair Shop. It was looked at by staff in a backroom for 25 minutes. They came back and told me that my camera was back focusing and that something in the camera was bumped out of place, which is understandable because I was using my camera intensively in Florida. When testing it, they used their own lens so it was not my lens at fault, but my camera body itself. So now, it is getting repaired.

Thank you again for the help.

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It makes sense that something was wrong inside your camera. There was something very funky going on in the bokeh of your camera that wasn't there on your fiance's camera.

That's why I thought it might have been some sort of contamination on your sensor. But, the anti-aliasing filter being loose makes sense.

[ebiggs1]

"Basically, I was not convinced that it was user error."

I am not going to belabor the point if you have a solution but back focusing only puts the focus point in a slightly different spot. It does not blur the entire photo.  In other words something in the shot should be in focus.  The problem is more apparent at wider apertures than smaller ones. It may disappear completely as the aperture gets very small.