Canon 70D and 70-200 F2.8L sharpness

amaFotho

amaFotho

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Michael
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Apologies for the cross post but I am confused by the lack of sharpness with my Canon 70D and 70-200 F2.8L lens :thinking: I took some test shots which seem to indicate that I need to use F5.6 or higher at 200mm with a subject 1.5m away, does this make sense ?

See my other post for my test images http://www.talkphotography.co.uk/forums/showpost.php?p=5851077&postcount=4 (which have not been cropped or pp in any way. I used spot focusing with the center point selected)
 
What's the minimum focus distance for the lens?
Was there any slight breeze?

I'm no expert but I would expect that you are testing focus too close to the lens. I think focus testing is recommended at no less than 50 times the focal length - ie at 10m in the case of 200mm.
 
Hi Michael.

You'll have to get used to this I'm afraid, at that sort of subject distance at 200mm the DOF is going to be wafer thin at pretty much any aperture below the diffraction limit of the sensor, and especially wide open as you have discovered.

Part of the "penalty" you pay for having the resolution and high ISO capabilities of a bigger sensor as opposed to a little point and shoot.

Keep experimenting, you'll get the hang of it.

David
 
According to the DOF calculator on Cambridge in Colour the DOF of a 200mm lens at F2.8 focussed at 1.5m is a whopping 1cm!

A F5.6 it's barely any deeper.

I have a 70/200 f2.8 l that I use on a 60D and a 5D3 and hand held I could easily move more than a centimetre, which on one shot focus, would easily throw the shot out of focus and make it look soft (very).

At anything less than 10m or so I use servo focussing to compensate for my body movement.

Darren
 
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I wonder how accurate Servo mode can be, presumably it's dependant on the lens focussing speed, the predicting capability of the camera software as well as the focus point detection on the sensor.
 
If you have a smartphone download DoF Master and you will have 'in your pocket' access to all you need to know. Select the Camera/Lens/Aperture/Distance from the drop down menus and "Voila"! instant near and far readouts.
 
Thanks for all response, too many to respond to just now but some further info
- used a tripod with 2sec timer delay to avoid any camera movement
- lens IS on
- lens set to "1.4m-infinity" focussing

Steeper learning curve than I ever expected 😄
 
Not that it'll make a huge difference, but you can (some say should) turn off IS when on a tripod - I know some lenses/bodies have a sensor so do this automatically.

Minimum focussing distance is 1.4m, so if the subject was 1.5m away it's pretty close, and if it was "about" 1.5m away, you might have been under.

DOF would also be tiny at that closer range.
 
drounding said:
I wonder how accurate Servo mode can be, presumably it's dependant on the lens focussing speed, the predicting capability of the camera software as well as the focus point detection on the sensor.
Click to expand...

You're right Duncan, on my 5D3 I can feel the lens gently changing focus as I breathe. I was taking some head shots of my wife the other morning and if I focused on an eye I could feel the camera changing focus if she blinked!

My 60D is not quite so sensitive, but even with the 60D I get more keepers at close to min focus with servo than single shot. perhaps I've particular shaky hands?

Darren
 
drounding said:
I wonder how accurate Servo mode can be, presumably it's dependant on the lens focussing speed, the predicting capability of the camera software as well as the focus point detection on the sensor.
Click to expand...

There are some very intersting articles on this over on the www.lensrentals.com/blog. It would seem that some of the older Canon lenses are just not capapble of using the full focusing capabilities of some of the newer bodies like the 1DX and 5D mkIII.

I leave my 70-200L in servo and use back button focus, but use that method with my 10-22 and lots of fuzzy photos :'(

David
 
Cheers all, will do some reading of DoF, back button focusing (and get the app) - had not appreciated that the DoF got that small :bonk:
 
A few have mentioned DoFmaster. Great tool, BUT it tells you what the DoF is of a 10"x8" viewed at a distance of 12". If you pixel peep and view it in a monitor at 100%, the DoF gets even smaller because you are viewing the print effectively much more closely...

Looking at the photos you posted on the linked thread, they all look equally sharp at the focus point in the resized versions that are posted in the linked thread, but not when viewed at 100% - that's exactly what you'd expect from theory.
 
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arad85 said:
A few have mentioned DoFmaster. Great tool, BUT it tells you what the DoF is of a 10"x8" viewed at a distance of 12". If you pixel peep and view it in a monitor at 100%, the DoF gets even smaller because you are viewing the print effectively much more closely...
Click to expand...

:thinking:

Sorry, what?
How would the depth of field change on a printed/viewed picture, after the photo has been taken?
 
I think he means more stuff appears to be sharper and in focus the smaller the image is. The DOF is always the same, obviously.
 
Durbs said:
:thinking:

Sorry, what?
How would the depth of field change on a printed/viewed picture, after the photo has been taken?
Click to expand...
Simply..

  • Everything off the plane of focus is actually out of focus - the further away it is the more out of focus it gets.
  • Depending on how big you print, and from how far away you view, will determine if you can see a point in the image as in or out of focus.
  • Depth of field is perceived (and depending on your eyesight, you may perceive it differently than someone else), NOT captured in the image

Have a look: http://photo.andysheen.co.uk/technical/depth-of-field-and-what-affects-it-explained/ and around wikipedia to get an idea of how and why it works the way it does and why sensor size plays an important fact in both DoF and sharpness.
 
Janesy B said:
I think he means more stuff appears to be sharper and in focus the smaller the image is.
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Yup (and the converse the larger the print, the more fuzzy it gets)

Janesy B said:
The DOF is always the same, obviously.
Click to expand...
Nope. DoF is NOT fixed into the image, it is something you perceive when the image is rendered on screen or in print. It is a consequence of your first statement ;)
 
My tuppence...

'Technically' DoF is a physical constraint, hence how it can be calculated. In practise the perception of the DoF of an object in an image is affected by ones eyesight and the dpi viewed.

If the DoF is very small then the effect on a small image view of a photo may be difficult to see, so much so that the object may perhaps seem OOF.

Many other factors are also involved as well such as the processing of the image and the jpeg quailty etc. etc.
 
drounding said:
'Technically' DoF is a physical constraint, hence how it can be calculated.
Click to expand...
It is calculated by making assumptions as to how good the eye is at discerning lines, how big the image is printed and how far away it is viewed. Go and have a look at wiki for the in depth maths, but the values come from calculations with assumptions about the human visual system.

So yes, it is a "physical constraint" in that it uses the physiology of the human body, but it isn't a physical constraint on solely the camera system (which is what a lot of people think when they view it as DoF being captured in the image).
 
Durbs said:
:thinking:

Sorry, what?
How would the depth of field change on a printed/viewed picture, after the photo has been taken?
Click to expand...

Because there is nothing at all fixed about DoF; There's a sharp plane of focus and everything else is perception of sharpness. That perception varies with image size and viewing distance.

For a simple proof of concept, how many 'sharp' pictures have you seen on your camera LCD screen that you binned once you'd downloaded them. That's not because your screen is inherently inaccurate, it's the size of the image and the viewing distance.

For a more scientific answer you can lose a day reading up on DoF and the circle of confusion.
 
If you want macro, get macro lens. 70-200mm is for portraits and action, and is really not meant to be used bang on at 1.5m. Having said that they are pin sharp wide open, technique dependent.
 
daugirdas said:
If you want macro, get macro lens. 70-200mm is for portraits and action, and is really not meant to be used bang on at 1.5m. Having said that they are pin sharp wide open, technique dependent.
Click to expand...

Fully agree*, to be honest I am playing with all sorts of pictures to work out what I like and enjoy taking.

As a rule of thumb, what is a minimum distance I should keep to with this lens?

* already looking at macro lenses or maybe extension tube with my 50mm as my wife keeps asking for a picture of this or that flower
 
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