topic Re: my 400mm 5.6 wont focus sharp in EF & RF Lenses

my 400mm 5.6 wont focus sharp

colin333 — Tue, 08 Jan 2019 19:57:33 GMT

Hi Guys

Appreciate any help here

I have my camera (5d mkiv) set up on tripod and trigger with my 400mm lens. It is set up as one shot with the center focusing point. I take a picture in live view at 25m and it is pin sharp, however when i use normal position it is not as sharp, I have gone thru the micro settings from -10 to +10 but still cannot get it as sharp as live view. Any suggestions would be most welcome

Re: my 400mm 5.6 wont focus sharp

ebiggs1 — Tue, 08 Jan 2019 20:48:20 GMT

"... it is pin sharp..."

This tells you it is not the lens or camera. That means you need to look elsewhere for the issue.

Re: my 400mm 5.6 wont focus sharp

kvbarkley — Tue, 08 Jan 2019 21:12:46 GMT

You need something like an AlignRite - or a yardstick at 45 degrees - to tell *where* it is focusing.

If it is severly front/back focusing, you can send it to Canon to be calibrated with your camera.

Does it Focus OK with other lenses?

Re: my 400mm 5.6 wont focus sharp

jrhoffman75 — Tue, 08 Jan 2019 23:36:04 GMT

@ebiggs1 wrote:
"... it is pin sharp..."

This tells you it is not the lens or camera. That means you need to look elsewhere for the issue.

When you focus using Live View you are looking at excatgly what the sensor is recording. If its in focus in Live View it will be in focus in the digital file.

When you are focusing through the view finder you are indirectly focusing the lens; you cannot actually see whether it is in focus or not.

If its "pin sharp" in Live View but not when you use the "normal" AF system it means there is a problem in the phase-detection AF system "flowpath". It could be badly out of adjustment or damaged, so that camera repair is necessary, or it could just need autofocus micro adjustment "AFMA".

https://cdn.static-bl.com/images/manual/Canon-AF-Micro-Adjust-Guide.pdf

Re: my 400mm 5.6 wont focus sharp

colin333 — Wed, 09 Jan 2019 07:18:49 GMT

i have not tried it with other lens, but will do - thank you

Re: my 400mm 5.6 wont focus sharp

colin333 — Wed, 09 Jan 2019 07:20:42 GMT

It is a brand new camera so I hope that isnt the issue. Could it be the mirror action that is sending it slighty out

Re: my 400mm 5.6 wont focus sharp

jrhoffman75 — Wed, 09 Jan 2019 12:08:31 GMT

With only one lens and camera yo cannot isolate the problem. Need to get an additional item and then see what happens.

Re: my 400mm 5.6 wont focus sharp

ebiggs1 — Wed, 09 Jan 2019 13:54:10 GMT

"This tells you it is not the lens or camera. That means you need to look elsewhere for the issue."

My intention was to confirm the lens and camera can be "pin sharp". That is why I suggested the OP look "elsewhere".

Re: my 400mm 5.6 wont focus sharp

TCampbell — Wed, 09 Jan 2019 18:22:22 GMT

You mentioned using center focusing point and getting a sharp result.

But then you said "i use normal position it is not as sharp".

What's "normal" position?

Are you referring to a different focus mode? Different focus points?

In "One Shot" mode the system only focuses until it achieves focus... then stops focusing. If anything moves after it achieved a focus lock, it does not re-focus unless you force it. In "AI Servo" mode it will continuously track focus.

As for focus points... if you force it to use a specific AF point, then that's the point it will use (you can also use AF point expansion or surround modes to increase the area, but again... it will stick to that cluster of points).

If you start to give the camera more freedom ... zone focus or allow all AF points... then the camera uses some rules to decide how to choose a focus point.

In typical One-Shot mode (if all AF points are active), it will typically try to find the AF point that can achieve focus at the CLOSEST focus distance to the camera. This means you would want to make sure there is are no focus points located on anything in the scene which is closer than your intended subject.

In AI Servo mode it will follow the rules based on the intelligent Tracking & Recognition system (iTR). You can do things such as set an initial point of interest and then select the "case" rule for how it should behave when trying to follow that subject around the frame and it will do its best to keep up. It will typically highlight (with a few squares) the points that are being tracked so you know what it thinks it is focused on. There are also rules about how it should behave when doing a burst of shots. Note that iTR is only active in viewfinder mode (not available if doing live-view) and also you must be using either zone-AF, large-zone-AF, or full auto-AF (all points active). It is not available if using spot, single-point, AF-expansion, or AF-surround modes.

If single-point AF nails focus for you... then my guess is when you say "normal position" you are letting the camera pick the AF point and when that happens, it has different rules to decide which AF point should be used. This isn't a big deal if you know the rules.

Re: my 400mm 5.6 wont focus sharp

colin333 — Wed, 09 Jan 2019 21:59:57 GMT

sorry for not explaining myself better.

So I took a picture of a static object with small lettering on at a distance of about 25m. the 1st picture was taken in live view. This was sharp and lettering was crisp.

I then took a picture through the view finder with the single center focus point selected, it was in one shot mode. this produced a picture with blurred lettering.

I went 10 points both negative and positive microadjustment, I did get a slightly more foccused lettering but not as good as I got in live view

Re: my 400mm 5.6 wont focus sharp

jrhoffman75 — Wed, 09 Jan 2019 22:03:51 GMT

An you go more that 10 points AFMA with that camera?

Re: my 400mm 5.6 wont focus sharp

colin333 — Wed, 09 Jan 2019 22:08:20 GMT

as i went further in either direction it seemed to get worse, so I didnt go any further

Re: my 400mm 5.6 wont focus sharp

jrhoffman75 — Wed, 09 Jan 2019 22:18:28 GMT

If I understand correctly you are getting your best result at 10 units of AFMA (worse results on either side of 10) but still not sharp at 10. That’s strange behavior.

Re: my 400mm 5.6 wont focus sharp

colin333 — Wed, 09 Jan 2019 22:39:49 GMT

yes best result was at plus 4 but not as good as in live view

Re: my 400mm 5.6 wont focus sharp

jrhoffman75 — Wed, 09 Jan 2019 23:24:36 GMT

Try this, using single AF point focus on a bright contrasty subject:

1. Focus with Live View. Note position of focus ring/scale.

2. Switch off Live View and half-press shutter button to focus.

3. See which way the lens focus ring moves - towards or away in distance from the LV position.

4. Move AFMA adjustment in opposite direction. If focus moved in direction of infinity add negative AFMA or vice versa

5. Repeat until lens doesn’t move between LV and viewfinder focus.

Re: my 400mm 5.6 wont focus sharp

TCampbell — Thu, 10 Jan 2019 01:01:53 GMT

Liveview focus and viewfinder focus use completely different focus systems. On a 5D IV it's a little different than older cameras because the 5D IV has Dual-Pixel CMOS AF.

In any case, Liveview focuses the image directly ON the sensor itself. The reflex mirror is "up" so the light can hit the sensor. When you shoot via the viewfinder, the reflex mirror is down ... light can't reach the sensor. The mirror bounces most light up to the viewfinder screen ... but there's a semi-silvered area in the middle of the mirror that lets some light pass through. A second (smaller) mirror is hiding behind the first mirror and this mirror is angled to bounce light down to the floor of the camera ... this is where the phase-detect AF sensors are located.

The theory is that if the distance light has to travel to go through the first mirror, hit the sencond mirror, bounce down, and reach the AF sensors is *precisely* the same distance that the same light would travel if the mirror were out of the way so the light could go straight to the sensor, then a focused image on the AF sensors would mean a focused shot on the camera imaging sensor.

But the sensor has to be shimmed into position to locate it at *precisely* the right point. And it turns out different lenses can also have different effects.

SO... the 5D IV (and most high end bodies) have Auto-Focus Micro-Adjustment that lets you tweak the focus to tell the camera to focus slightly closer or slightly farther than it otherwise would.

There are focus calibration tools (X-Rite makes one called the "LensCal"). LensAlign is another popular tool. They both work very similar to each other.

The idea is there is a flat target that you use for focus.

Adjacent to the flat target is something resembling a yardstick or a ruler .. except it is resting at an angle (like a ramp). It has a scale on it.

You point the camera at the FLAT target (not the ramp) and take the shot. But when you pull the photo into your computer, you inspect the focus on the ramp ... to find the spot where you think focus is the best. This might be either closer or farther than the flat target (or it might be bang-on accurate).

As you see how these things work... you could acctually just use a flat target and rest an actual yardstick at a ramped angle immediately adjacent to your target (make sure the AF point is actually ON the target ... not the yardstick.)

You should be able to adjust the camera for each lens so that it nails focus. I actually suggest deliberately de-focusing the lens so that focus is deliberately closer than the target... make the camera adjust focus outward to achieve focus and take the shot. Repeat this a dozen times. THEN... deliberatetly run the focus out too far (toward infinity) and make it adjust focus inward to achieve focus and take the shot. Also repeat a dozen or so times.

Just a single sample could just have a freak incident... but if you take a dozen samples in each direction you *should* be able to see a trend and you want to adjust the camera based on the sweet spot in that trend.

If focus is all over the place (there is no trend) ... try a different lens (the lens may have sloppy mechanics and require service).

If the focus is all over the place regardless of lens... send in the camera (and you may want to send the lenses along).

If the camera is so far out of focus that even the limits of the AFMA can't correct for it ... send the camera in for service (sensor probably needs to be re-shimmed to the correct spot.)

Re: my 400mm 5.6 wont focus sharp

kvbarkley — Thu, 10 Jan 2019 01:20:38 GMT

I hope you are using a tripod

Re: my 400mm 5.6 wont focus sharp

Waddizzle — Thu, 10 Jan 2019 01:28:07 GMT

@colin333 wrote:
yes best result was at plus 4 but not as good as in live view

Maybe you do you need an AFMA adjustment, but I would doubt it with new gear. But, who knows?

Follow Tim’s suggestions on setting up a target. You need to be about 25-50x the focal length, so you seem to be at a good distance. I think 50x would be better, though. For super telephoto lenses, I like to use either a yardstick or a tape measure.

Check the focus range settings on the lens. You can get soft images if it is set to the wrong range. Which way should you adjust the lens, with a positive or negative value? The answer is pretty simple. Think of the AFMA value as a correction to the focusing distance.

If the lens is back focusing, then enter a negative value to bring the distance to the plane of focus closer. If the lens is front focusing, then enter a positive value to increase the distance from the camera to the plane of focus.

I have found that the “Dot Tune” video on YouTube to be very simple to use. It takes all of the guess work out of making an AFMA. Just take numerous sample shots, and calculate an average. Hope this helps.

Re: my 400mm 5.6 wont focus sharp

colin333 — Thu, 10 Jan 2019 07:01:59 GMT

Thanks guys, I will have to try this at the weekend as it is dark when I go to work and dark when I come back.

The camera is new but the lens is a few years old

thanks again, I will get back

Re: my 400mm 5.6 wont focus sharp

jrhoffman75 — Thu, 10 Jan 2019 12:19:17 GMT

Do you have another lens? Then you could at least rule out the camera.

Can you describe what you are trying to photograph?