Slightly Unsharp Images

Just a bit of a general question if may folks....

I went wandering in the woods today with the 70-200mm f/2.8L mkII on my Canon 6dmkII.

I took about 20 pics, all on a tripod and all with a 2 second timer.

Most have them don't really have any sharpness to them at all when zoomed in. I took various f stops from 2.8 up to about 18 and ISO100.

The one thing I did do which I saw in a youtube video, but never done before, was to use a polarising filter. I have to admit that when turning it, I could see no difference at all. The idea from the video, was that it would add more warm to the images.

Do you think this may have been the cause of the images not too sharp?

Thanks all

Some samples would be good.

Why are you zooming in to look for sharpness? You zoom in to fix problems, not to look for them. If you zoom in far enough on any photo, regardless of the hardware used to make it, it will, eventually, appear soft.

You can see a difference with a polarizer when turning it while looking at something with reflection, water, glass, shiny surfaces. If you are in a darker area and, or, there are no reflective surfaces, you probably won't see much of a difference. It won't make your pictures 'warmer'....at least not by my definition. It will reduce or eliminate reflections and it can make your colors a little brighter.

tuttifrutti wrote in post #18781574
Just a bit of a general question if may folks....

I went wandering in the woods today with the 70-200mm f/2.8L mkII on my Canon 6dmkII.

I took about 20 pics, all on a tripod and all with a 2 second timer.

Most have them don't really have any sharpness to them at all when zoomed in. I took various f stops from 2.8 up to about 18 and ISO100.

The one thing I did do which I saw in a youtube video, but never done before, was to use a polarising filter. I have to admit that when turning it, I could see no difference at all. The idea from the video, was that it would add more warm to the images.

Do you think this may have been the cause of the images not too sharp?

Thanks all

Sample images would help.

Speaking from my own experience, when on a tripod, I turn the IS off because I used to have the same problem at times.
Here is an article that may shed some light onto your issue.https://cpn.canon-europe.com …es/image_stabil​isation.do

Polarizers help on blue sky with a little haze, but only at certain angles to the sun/haze.

Any additional glass can effect sharpness, cheaper filters more than better filters. And yeah, without good 100% examples and exif, the sharpness problem/solution is just guesswork.

Thanks all for the very quick replies.

Here's a link to the album on Flickr - i you don't mind, i'll let you have spooky and make your judgements on what you see. Maybe i'm being over-critical but up until now, i've only really used this lens for fast action sports and it's been tack sharp, so was expecting the same from today's images

https://flic.kr/s/aHsm​yjneon

Again, thanks all for your replies s far

I see some motion blur in a couple....maybe a breeze moved the ferns. The one with the barbed wire is sharp.

Img 009 is simply not focused on anything.....not sure what you did there. Img 010 has a point in focus but no depth of field. Please know that depth of field is affected by not only aperture but distance between you and your subject, distance between your subject and focal length.

I don't really think any of these pictures display a problem with your equipment.

Thanks for taking the time to have a look Bob, much appreciated.

I have to say, now i've looked at them again, you could be right in all that you say. A few of these did have between 2-5 seconds so could well have been a bit of blur.

Also noticed that many of these I shot at f/2.8 which is a bit disspointing when a) I had all the time in the world to think things through, and b) I didn't really need such a low depth of field considering I needed a lot more of the subject in focus.

Real schoolboy errors there

tuttifrutti wrote in post #18781598
https://flic.kr/s/aHsm​yjneon

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Ok, so I see the fern picture, shot at f5.6 and that seems ok?

But multiple other shots are at f18 - wowsers, that increases your Depth of field, but that also brings in light diffraction - this happens at tighter/higher fstops.

Basically, images shot at 5.6 will be sharper than the same item shot at f18 due to physics of light and whatnot.

one of many spots that talk about light diffraction:

Light Diffraction Calculator

Google light diffraction to find resources, and somewhere it will be explained so it makes sense to you.

And then the IS needs to be OFF when on a tripod has been mentioned.

Another possibility is that use of a cheap filter can harm IQ

Thanks so much for that.

I'm learning all the time.

I had no idea that shooting at f18 would be any different to f5.6 with regards to sharpness. I assumed I would just be getting more sharpness from corner to corner rather than shooting at f2.8.

I will have a read about light refraction later when I get a mo.

So is this situation more dependant on whether I'm in woods or a dark location as opposed to being in good light, as if not, I don't understand why higher than say f11 Is offered in a lens?

Thanks again for your comments and advice all

tuttifrutti wrote in post #18781717
So is this situation more dependant on whether I'm in woods or a dark location as opposed to being in good light, as if not, I don't understand why higher than say f11 Is offered in a lens?

A smaller aperture than f/11 is offered because sometimes you need to reduce light because you are unable to select a faster shutter speed (or you are shooting with film which does not permit you so easily choose a slower ISO rating!) But f/11 is NOT ALWAYS going to result in diffraction degradation...it happens with the smaller APS-C format, might not happen until f/16 with the larger FF size, it does not happen with medium format until f/22, and with even larger format it might not be seen until f/45...because while diffraction is 'the same' for all formats with a larger format you do not have to MAGNIFY the image as much in order to make the same size print!...the diffraction is still there, it simply is not yet 'oobjectionable' in magnitude with larger formats.

I agree with Wilt.

I have seen this 'diffraction warning' thrown around way too freely. ".....you're going to degrade the image at anything above f8...'. I've shot at f 18-22 more than a few times and the images show no ill effects. I wouldn't be too worried about diffraction.

I did this comparison of diffraction effects quite a while ago...

https://photography-on-the.net …showthread.php?​p=11920404

While it's common for lenses to be sharpest at f8 or f11, the 70-200 2.8 II is sharper at f5.6 than at f8.