70-200 f4L - not sharp when open...

[JusSmith]

Just cannot get a sharp picture with this lens opened up (f4 or f5.6). Took some test shots at the weekend and used the Depth of Field calculator which says both have about 4-5 inches DOF. Yet the second looks alot better than the first (especially the hair). As I said, this happens with all open shots, not just this example.

The first was 1/800s, f5.6, 200mm, iso 100, 15ft from subject, 100% crop of centre focus point...

http://www.pbase.com/jussmith/image/41926046/large.jpg

The second was 1/500s, f8, 110mm, iso 200, 7-8ft from subject, 100% crop again from the centre...

http://www.pbase.com/jussmith/image/41926047/large.jpg


Is the 70-200 f4L not as sharp as reported when open? What else could be the problem?

Many thanks in advance for any comments.

[JusSmith]

What am I doing wrong with the 'Insert Image', it doesn't embed on the page?

The links are http://www.pbase.com/jussmith/image/41926046 and http://www.pbase.com/jussmith/image/41926047

[roanjohn]

Add ".jpg" at the end of the link :-)

This is one of Canon's sharpest zoom lens. I think that you have to post process your shots to maximize its potential. Even at f4, my copy is sharp as tack.

BTW, your shots don't look bad..........but this could be due to my crappy work monitor.

Ro1

[JaertX]

It looks to me like your focus is off in the first picture.

The stray hairs in the upper right hand corner of the picture are sharper than the eyebrows.

Hope that helps?

[JusSmith]

Is it PBase not letting me do this? Ah, just realised, haven't paid up, still on trial, must be that!

[JusSmith]

It looks to me like your focus is off in the first picture.

The stray hairs in the upper right hand corner of the picture are sharper than the eyebrows.

Hope that helps?

This is where I'm confused, it's consistently out of focus below f8, so that might point to some front or back focusing problem of the lens. But when I take another picture at f8 or above and adjust zoom/distance of subject (in an effort to get roughly the same DOF) it looks fine. So it can't be front/back focusing with the same DOF?? Or am I on the wrong wavelength here?

Cheers for all comments, please put me right when I'm being stupid!

[mr.photoguy]

Try to put the Center Dot on one of the eyes, and only use the center dot for focus.
Use F4, and then usm the image in CS, and let us know what you get.

Take some test shots also.

[JusSmith]

Fixed the problem by coughing up my $23 to PBase.

Thanks Mr. Photoguy, I'll do some more tests.

[JMAS]

It is sharp alright.
http://images.fotopic.net/?iid=ys59kk&outx=760&oq=0&original=1&noresize=1&nostamp=1

Check if you have the focus button (up to 1,2m; greater than 3m) adjusted to the correct focusing distance, or if you are at the minimum distance required for taking the shot.

[roanjohn]

Check if you have the focus button (up to 1,2m; greater than 3m) adjusted to the correct focusing distance, or if you are at the minimum distance required for taking the shot.

Good advice!!! The first shot................the hairs on the ear seemed more focused than the face..........could be back focus issue.

Ro1

[Mike H]

Be careful about your focus point. The depth of field for your first shot (200mm, f/5.6, 15') is about 4 inches. If you focus with the center point and then recompose the shot you will move the focus point away from your subject when you recompose, probably by a couple of inches--just enough to have the subject slightly out of focus.

Try this: pick an AF sensor that is close to the main subject so that you don't have to focus and recompose.

I have that lens and it's terrific. It's solid as a rock, focuses well, and is one of the sharpest that Canon makes.

An easy-to-use online depth of field calculator can be found at the link below:

http://www.dofmaster.com/dofjs.html

A good discussion of the "focus lock and recompose" method can be found at this link:

http://visual-vacations.com/Photography/focus-recompose_sucks.htm

Good luck.

[JusSmith]

Mike H - yep, good point, I or the subject may have moved more in the first pic than the second. Guess I ought to test with these out of the equation, ie tripod and static subject.

[griff2]

Came upon this problem with my 70-200 f/4 yesterday, but it tunred out my shutter speed was just too low: I forgot to factor in the extra zoom because of cropping (on 300D) and ended up with lots of soft pictures due to motion blur:evil:

I've attached a modified spreadsheet which I posted earler on this forum, and which will calculate the depth of field for a given focal length and aperture.

[JusSmith]

Came upon this problem with my 70-200 f/4 yesterday, but it tunred out my shutter speed was just too low: I forgot to factor in the extra zoom because of cropping (on 300D) and ended up with lots of soft pictures due to motion blur:evil:

I've attached a modified spreadsheet which I posted earler on this forum, and which will calculate the depth of field for a given focal length and aperture.

griff2 - do you mean the 1.6x factor for Canon digital? What were your shutter speeds? I thought mine of 1/800s would be ok to rule out motion blur or am I wrong?

[griff2]

JusSmith wrote: griff2 - do you mean the 1.6x factor for Canon digital? What were your shutter speeds? I thought mine of 1/800s would be ok to rule out motion blur or am I wrong?
Yes the 1.6 factor. I was using 1/200 instead of at least 1/320:rolleyes: The softness in your images is definitely depth of field related and not motion blur.

[roanjohn]

griff2 - do you mean the 1.6x factor for Canon digital? What were your shutter speeds? I thought mine of 1/800s would be ok to rule out motion blur or am I wrong?

There would still be blur if your movement was rated at 1/900s!!! :lol: :lol: :lol:

j/k.

Agree with all the other post. Try not to shoot and recompose. At these focal lengths, nailing your target is a bit tricky........and will take some practice.

Ro1

[JusSmith]

Cheers everyone, as ever the best advice can always be found ar POTN

[tim]

Do the same test I did in this thread (http://photography-on-the.net/forum/showthread.php?t=66959), on a tripod, and post the result.

[mr.photoguy]

So have you had any luck.
I still have like 50 images I have to edit, that were taken with my 70-200 f4. I am so behind on my editing.

[JusSmith]

Hopefully get the some shots off tonight with the tripod. Don't have a tripod ring, but the lens feels so secure against a 20D, do I really need it? Had a 300D last week (got my 20D on Friday) and that felt like I shouldn't have it on a tripod without a ring with the 70-200!

[mr.photoguy]

No, you won't really need it.

Only one time that I needed it was on a windy night, when I was trying to do some shots of the Triborough bridge, but then @ 200mm I would have had the blurriness no matter what .. meh.

[weemannie]

Just a thought, have you got a filter on the lens? I've read that there can be sharpness issues when UV filters are used on this lens for some reason.

[mr.photoguy]

http://www.pbase.com/brucescott/image/41985565
http://www.pbase.com/brucescott/image/41985564

can you tell which has a UV filter, and which doesn't?

I just did these today.

[blue_max]

65 seems darker. Don' t know what that means re filtes though.

Graham

[mr.photoguy]

yeah 1 has a UV, and one doesn't.
I was seeing some little horizontal, and veritcal lines on my images, and was curious as to what the heck they were, so I figured I would do a test to see..

but not trying to hijack the post... so...

[Mike H]

Hopefully get the some shots off tonight with the tripod. Don't have a tripod ring, but the lens feels so secure against a 20D, do I really need it? Had a 300D last week (got my 20D on Friday) and that felt like I shouldn't have it on a tripod without a ring with the 70-200!

The need for a tripod ring is situational. In bright light you won't need a monopod or tripod, but in dimmer light those will come in handy. I have the ring for my 70-200/4L and really love it. Mounting the lens and camera is really quick with the ring. Also, it causes the whole rig (camera plus lens) to balance well on my tripod and ball head, and rotating from vertical to horizontal is quick and easy. :-)

[JusSmith]

Just taken some indoor shots with the tripod and the pictures look a lot sharper (sorry, don't have time to process them yet, just viewed using EOS Viewer Utility). I did get it a smidgen sharper with manual focus, but it was low light conditions (1/30s at f4, ISO 400) so I should give the lens the benefit of the doubt. Tested 70mm and 200mm zoom from between 20 feet and 5 feet.

Looks like it is my technique!

I'll setup a proper 45 degree ruler shot in daylight to confirm that my 70-200 is working fine.

[JusSmith]

The need for a tripod ring is situational. In bright light you won't need a monopod or tripod, but in dimmer light those will come in handy. I have the ring for my 70-200/4L and really love it. Mounting the lens and camera is really quick with the ring. Also, it causes the whole rig (camera plus lens) to balance well on my tripod and ball head, and rotating from vertical to horizontal is quick and easy. :-)

Mike - think I'll get one as I'm planning on getting the 1.4x extender, so as you say, the balance will be alot better.

[JusSmith]

Just a thought, have you got a filter on the lens? I've read that there can be sharpness issues when UV filters are used on this lens for some reason.

Yes, I do use a filter, Hoya Pro 1 though, so not a cheap one!

[weemannie]

Yes, I do use a filter, Hoya Pro 1 though, so not a cheap one!

There was an article in EOS magazine sometime ago about it, (Can't find it now!:( ) where from memory it stated that some lenses have a problem regardless of the quality of the filter, and that they could find no apparent reason for it.

Just thought it might help to mention it. :)

[JusSmith]

Cheers weemannie, I'll definitely have a go without the filter now and see if it makes a difference.