Is my 7D & 300 f4 sharp?

redmonkee

redmonkee

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PHILIP
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I've never been good at judging if a lens is sharp so I'd love your thoughts on the 100% crop of the image below.

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This was set up at the end of my drive approx. 10m away. Camera was tripos mounted. I used centrpoint AF with mirror lock up, though I didn't have a cable release to hand. Oh and it was taken at F4 at 1/1000

Heres the crop

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any good?
 
I think that's okay - remember the anti-alias filter on the 7D is fairly harsh and 18MP is asking a lot on the 300/4 wide open.
 
redmonkee said:
Hi Andy

does Ok mean sharp then or just ok:thinking:

and what's the anti-alias filter:shrug: sorry if that's a dumb question lol

oh I think I should mention I have not added any sharpening to this image, this is straight from the camera
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I think okay is 'as much as you can reasonably expect'. The AA filter is a piece of glass that sits over the sensor. Its purpose is to very slightly blur the image hitting the sensor. This prevents diagonal lines appearing jagged ('aliasing') and also prevents high-frequency (i.e. slightly higher than the pitch of the pixels) resulting in moiré (remember the grey-flannel check suits on the TV in the seventies and eighties and the mad patterns they produced). Moiré is very difficult to (actually impossible to completely) remove in software without a priori knowledge of what you are shooting.
AA filters also help prevent colour artefacts appearing when you 'de-mosaic' from the separate Red, Green (and another Green) and Blue pixels in the sensor array by spreading the light out a bit so a single point of light can't just hit, for example, a single colour of pixel.

So, AA filters are good... But they reduce absolute resolution. So you can never truly get 'pixel-level' sharpness.

When I say 'harsh', I mean the degree of blur of the 7D sensor is a little harsher, per pixel, than you see on your 5D.

Andy
 
Second time today I've asked someone if their test shot has been unsharp masked...

As I said elsewhere Canon say:

Canon EOS digital cameras have an anti-aliasing filter installed on the image sensor.
This filter improves color rendition and practically eliminates moiré. The liability is a
slight reduction of sharpness. To reduce the softening effect of the anti-aliasing filter we
recommend applying an unsharp mask to the image in Adobe® Photoshop
Click to expand...
 
redmonkee said:
Hi Andy

does Ok mean sharp then or just ok:thinking:

and what's the anti-alias filter:shrug: sorry if that's a dumb question lol

oh I think I should mention I have not added any sharpening to this image, this is straight from the camera
Click to expand...

I noticed just how soft the 7D images looked straight from camera (RAW), but they do scrub up exceptionally well with a little USM in PS.
 
It's worth remembering that 18MP on the 7D is same pixel pitch as 46MP on a full-frame - this is going to push your lenses hard.

Take the 100mm f2.8 L USM Macro. This is (and should be) one of the sharpest Canon lenses you can get. I don't think it is unreasonable to say that the 300/4 won't be as sharp as the 100 macro...

Now look at the results for the macro lens on a 50D (15MP):

http://www.dpreview.com/lensreviews/canon_100_2p8_is_usm_c16/page3.asp

Wide open, it can't quite reach the nyquist frequency of the sensor-lens combination. (This is the point where the maximum possible sharpness is obtained - the sensor, rather than the lens, is the limiting factor). Bearing in mind the 7D is 18MP - the macro lens will be slightly further from the nyquist limit for the 7D.

Obviously, stopping down, and the macro now out-resolves the sensor. But you see my point - it really is a big ask to get your 300/4 lens to not be the limiting factor in the sharpness when it is used wide-open.

It's been said by others - treat the 7D like a 10 or 12 MP camera with really good AF, noise and DR, and you'll be happy. Start expecting miracles, and you won't.

Andy
 
redmonkee said:
No it hasn't has unsharp mask applied. Can I ask what settings you would typically apply to a 7D file using this sharpening method?

Cheers
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Depends on the output, USM is generally the last thing I do before saving for web, but generally around 30% and radius of 0.5 as a starter for an 800 pixel image.
 
redmonkee said:
No it hasn't has unsharp mask applied. Can I ask what settings you would typically apply to a 7D file using this sharpening method?
Click to expand...

USM isn't an exact science, there are lots of variables to think about when making the settings (final image size, whether its for screen or print etc). However, the main tip is to make USM the last step of your process... so tweak colour, levels, whatever, resize and then hit USM just before you save the file.

Just playing a little with it, it does sharpen up a fair but with USM, however the 100% crop is still showing a fair bit of CA'ing. Did you have a UV filter on the lens?
 
desantnik said:
USM isn't an exact science, there are lots of variables to think about when making the settings (final image size, whether its for screen or print etc). However, the main tip is to make USM the last step of your process... so tweak colour, levels, whatever, resize and then hit USM just before you save the file.
Click to expand...

:thumbs:

It's also important, if you subsequently have to downsize a JPG for the web (you really should go back to the RAW file!!), that you re-sharpen the downsized image, or, again, it will look soft.

Andy
 
desantnik said:
Just playing a little with it, it does sharpen up a fair but with USM, however the 100% crop is still showing a fair bit of CA'ing. Did you have a UV filter on the lens?
Click to expand...

That looks like purple fringing rather than lateral CA (e.g. on the white letters of the soup can against the black). That may indicate a slight back-focus as the 300/4 does tend to show a bit of longitudinal CA (bokeh fringing - purple in front, green behind) when wide open. Or it may be the focus point isn't on the can...
 
From my own experience (with the 300f4 IS) the dreaded UV filter can also exagerate PF/CA too ;-)
 
desantnik said:
Second time today I've asked someone if their test shot has been unsharp masked...

As I said elsewhere Canon say:
Click to expand...

If ALL Canon EOS cameras have that as the article says (although I still see a quite a bit of moire on mine) then it may explain why the images look a bit soft when I pixel peep.

Not everyone has photoshop though so can ordinary sharpening fix this or does it have to Unsharp in photoshop? And why call it unsharp if its sharpening? :thinking:
 
trencheel303 said:
If ALL Canon EOS cameras have that as the article says (although I still see a quite a bit of moire on mine) then it may explain why the images look a bit soft when I pixel peep.
Click to expand...

:thumbs:

Not everyone has photoshop though so can ordinary sharpening fix this or does it have to Unsharp in photoshop?
Click to expand...

Some sort of proper image editing suite is essential if you are going to get the most out of your photos. USM is not just an Adobe photoshop feature...

And why call it unsharp if its sharpening? :thinking:
Click to expand...

http://en.wikipedia.org/wiki/Unsharp_masking
 
redmonkee said:
I did have a UV filter attached.
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Save the UV filter for the times that you think your lens might take a battering. Rest of the time, keep it in the box.
 
redmonkee said:
I did have a UV filter attached.

are you saying the 300 f4 is too good for the 7D??? i've seen the 7D paired with the 300 2.8 and the images from that are truly stunning:thinking:
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The 300/4 is a good lens. The 300/2.8 is a better lens. If you pixel-peep on the 7D, neither will look that amazing. Best not to...

Andy
 
redmonkee said:
I have Adobe CS3 and Adobe Lightroom 2. which one would you use to sharpen with?
Click to expand...

Well, personally, I only use lightroom to catalog and grade my images, everything else I do with Photoshop. Lightroom has basic controls, but nothing like photoshop does.
 
I guess I'll have to look into using a USM as well, and I'm now wondering whether the soft images my camera produces aren't focus problems at all but just by design. Gonna do some tests when I get that tripod me thinks...
 
redmonkee said:
Does this go for all camera/lens combos?
Click to expand...

Not exactly. The Canon L lenses are designed for full-frame. Most will easily out-resolve the full-frame sensors like the 5D mk2. Pixel peep on the 5D, it'll look very good (the pixels are larger).

Some cameras (like mine) have lenses only designed for the smaller sensor. E.g. the Olympus super-high-grade lenses are designed to out-resolve a 20MP fourthirds sensor (which doesn't yet exist!). Pixel peep on those lenses on a fourthirds body, it looks very sharp. In the same way as pixel peeping with a full-frame lens on a full-frame body is sharp...

Check out the example of my 300/2.8 with a 2x TC on as well here:

http://www.talkphotography.co.uk/forums/showthread.php?t=213231

Edit: It's also true if you pixel peep on say, a 40D with the 300/4 - the lower pixel pitch (40D has the pixel pitch of about 25MP on full-frame) is comfortable for the lens.

Edit 2: It might look like the 7D has too many pixels to be useful - and there is an argument that says that had Canon reduced the number and given better dynamic range and per-pixel signal-to-noise, that would have been better. However, the extra pixels do help by reducing the appearance of de-mosaicing artefacts (i.e. taking the 4 coloured pixels to work out what the actual colour is at a given point) by virtue that those artefacts are smaller relative to any detail you will see at a given print size.
 
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