5D mkiii video focus issues

[conran]

Hi everyone, 

My first post and i'm hoping to find some help.

Recently i've been seeing issues with focus on my 5dmkiii. The image looks sharp on the LCD (at maximum zoom) but soft when i check the file on the desktop. It's across all lenses and all picture modes.

I've been using 5D's for a few years now but this has me stumped. Any help would be much appreciated.

thanks

Jamie

[conran]

Cheers Tim, what could those other factors be?

It's been tested in studio conditions with lots of lights and in daylight too.

The shot shave DOF but the supposed point of focus is still soft.

[TCampbell]

Ordinally "other factors" might be blamed on issues with the lens' optical quality.  But since you are satisified with the results from a still image, it's clearly not the optical quality.

If you still suspect the camera is missing focus then you'll need a better focus target.  I use a Spyder LensCal.  The device has a flat card with a high-contrast focus target.  Adjacent to the target is a rule.  But the rule is leaning back at a 45º angle.  The 0 point on the rule is in the middle and this point is at the same distance as the face of the flat focusing target.  Since the scale is leaning on a 45º angle, if the camera is either front-focusing or back-focusing then you would notice that some other point on the scale has better focus than the 0 point in the middle.

Here's the website with a picture of the card:  http://spyder.datacolor.com/portfolio-view/spyderlenscal/

The other focus calibration tool I've seen is the LensAlign -- it's very similar to the Datacolor product in how it works.

The major purpose of both of these products is to provide a tool to help you perform auto-focus micro-adjust (on cameras that support it -- such as your 5D III.  Although micro-adjust only applies to focus performed by phase-detect AF sensors... it is not used when using live-view or video since that uses contrast-detect AF.)

Since your focus target is a simple flat card, you cannot easily tell if there is some point in space closer than your card that had better focus... nor can you tell if there is some point in space behind your focus target that would have better focus.  Although... in looking at your setup, it does appear to me that the focus target has better focus than other areas - it's just not possible to be precise.

[TCampbell]

Without looking at your LCD image and comparing to our computer screen image it would be hard to say why this happens.

BUT... the LCD is small.  Small images always tend to look sharper than large images.  The 3.2" LCD screen is merely a 1MP display.  Each single pixel of the LCD literally represents 22 pixel of image -- when you have to resample 22 pixels down to just 1 pixel it's difficult to use that to judge image quality.

[Peter]

Any example?