Resolution issue & Canon 1.4x TC

I've come across a bit of a puzzling situation, and recently learned that a fellow photographer experienced it as well:

I upgraded several months ago to a Canon 7D, as did he, although he has also added a 1D MkIV. Although he also uses a 500/f4, one of his primary lenses like mine is a 400/f4 DO. We both use Canon 1.4x II converters, as well as Tamron SP 1.4x converters and we've both recently experienced "softness" of our images when shot at full raw resolution with the Canon 1.4x and the 500 and 400DO lenses. Yet when the same lenses are used with the Tamron 1.4x converters, images are fine. What are the odds of us both (from different areas of the US) experiencing similar softness issues with the Canon converters, and none with the Tamron converters?! I also shoot with a 40D, and the combination of the 400DO and either the Canon 1.4x or the Tamron 1.4x delivers fine, sharp images.

My theory is that the pixel density of both the 7D (18 mp) and the 1D MkIV (15 mp?) sensors appear to be more than what the Canon converter can handle. Would it make sense to set the 7D raw setting to M-Raw which makes the image size approx 10 mp or roughly the same size as the 40D sensor?

Hi Chris,

What I would do first is test the focus adjustment under a controlled test. You might want to give Arash's focus calibration a try. It could be that the Canon TC is causing the camera to front or rear focus.

Here's the link to his test procedure: http://www.birdphotographers.net/for...ad.php?t=58042

I seriously doubt the Canon TC is being out-resolved.

Alan

FWIW I had big problems with my Mark IV, my 500 f/4, and my Canon 1.4x this morning! Still trying to sort things out.

Hi Doug,

Did you try it w/o the TC? Interesting.

Alan

Quote:

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Originally Posted by Alan Stankevitz

Hi Chris,

What I would do first is test the focus adjustment under a controlled test. You might want to give Arash's focus calibration a try. It could be that the Canon TC is causing the camera to front or rear focus.

Here's the link to his test procedure: http://www.birdphotographers.net/for...ad.php?t=58042

I seriously doubt the Canon TC is being out-resolved.

Alan

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Alan -

If the Canon TC is causing the 7D to front or back focus, why wouldn't it do the same with my 40D? Images made with both the Canon & Tamron TCs are fine.

Chris,

I'm not sure but it still might be worth checking it out. Firmware changes from camera model to camera model.

At least if you check the focus, you'll know if the resolution/sharpness is there or not. It's a pretty easy test.

Alan

Chris,

I had 400DO for a little while before I got the 500 it was tact sharp naked but not so good with 1.4TC on my 7D, or at least it did not meet my standards of sharpness.

1.4 does work well with 500 on 7D though, there is a little bit loss of quality but not very noticeable. It is true that when you view the photos from 7D at full size they will appear slightly softer than 40D because of extra-tight pixels and MLA that is on top of that, but 1D4 has the same pixel size as the 40D so files from that camera should look sharper and nicer.

It is possible that the TC performs well on the 40 but needs adjustment on the 7D because the AF sensors are different, and they are calibrated differently, so I would do a quick MA to verify.

checkout this thread here, I posted 100% crops of a dollar bill with 500 + TC wide open and Doug also provided some samples, you can compare yours against these samples, should be getting as good as these!!! good luck :)

http://www.birdphotographers.net/for...ad.php?t=55413

Thanks everyone for your assistance! I'll be doing a controlled test in the next few days and see if anything improves. I'm also going to set the 7D at the 10 mp M-Raw size as well and try it there. Fortunately I have the benefit of having the Tamron SP TC, which delivers nice sharp images when mounted on the DO and either the 7D or 40D. If the Canon 1.4x continues to give me problems, I'll ship it off to Canon.

Chris I have the same problem with my 7D and 1.4X TC II whereas my Kenko 1.4 is fine.

I have had the TC checked by Canon and done the MA but the images are still unacceptably soft and I no longer use the Canon TC on the 7D.

Sad but true.

Chris
unlike with lenses, Canon can NOT correct/adjust the focus on a TC
i have two 1.4 xTC's and wanted the older one adjusted to match the newer one - I was told there's nothing they can do with the optics in a TC

Quote:

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Originally Posted by Chris Brennan

Alan -

If the Canon TC is causing the 7D to front or back focus, why wouldn't it do the same with my 40D? Images made with both the Canon & Tamron TCs are fine.

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For what it is worth, on my Mark III I had to microadjust the 500/1.4xTC combo to +4. The bare lens was fine without adjustment. On the Mark IV, the same lens/TC combo does not need microadjustment.

Quote:

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Originally Posted by Peter Hawrylyshyn

Chris
unlike with lenses, Canon can NOT correct/adjust the focus on a TC
i have two 1.4 xTC's and wanted the older one adjusted to match the newer one - I was told there's nothing they can do with the optics in a TC

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Peter -

That's interesting because I've already spoken to a Canon Factory Service Tech here in the US who said that they can make adjustments to the Series II models. If yours are the earlier models, then I understand you are out of luck.But if they're the newer ones, you might consider sending them over the border to us...

Chris
good to know - they are both the newer Series II models
i'll enquire again at Canon Canada
thanks for the info

Not a controlled experiment, but this is what I've been experiencing. Both are 100% crops of unprocessed RAW files. The Osprey was shot with a bare 500 from a pontoon boat. The Caracara was photographed from land with a 500 and a 1.4x. I've never had a problem with this 1.4x before, and I've shot it on many bodies.

And here's the Caracara.

Quote:

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Originally Posted by Doug Brown

Not a controlled experiment, but this is what I've been experiencing. Both are 100% crops of unprocessed RAW files. The Osprey was shot with a bare 500 from a pontoon boat. The Caracara was photographed from land with a 500 and a 1.4x. I've never had a problem with this 1.4x before, and I've shot it on many bodies.

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Where is the Caracara?

Oh sorry I see now! what's going on :eek: ??? Did you try LV focus to see if it makes a difference?

Doug -

Your caracara shot illustrates perfectly what I'm experiencing with the 400DO + the Canon 1.4x on the 7D at full raw resolution. It's just soft, and it makes me wonder whether the Canon 1.4x just isn't capable of resolving fine detail with these denser (18 mp) sensors. I've not been able to get an acceptable MA with the Canon 1.4x and the 400DO, but results from the Tamron have been fine so it just doesn't appear as a front/back focusing issue..... it's all quite bizarre! But I'm very glad I've got the Tamron to use!

To some degree the degradation from a 1.4x TC on an f/4 lens is due to diffraction and the 7D pixel spacing is in the range where this should be apparent. The main effect will be loss of contrast at the pixel to pixel level, although the Caracara image Doug posted seems a little more degradation than I would expect.

Here is a graph showing loss of contrast:
http://www.clarkvision.com/articles/....html#DIFFRACT

It would be nice to see images using the Tamron and the Canon TCs on the same lens and target.

Roger

Roger -

Thank you for weighing in on this... I was actually waiting for a response from you because your deep technical and scientific knowledge on digital photography is unparalleled, IMHO.

It just occurred to me that the lens I'm using is a 400mm f4 DO which already has a penchant for diminished contrast and between using the higher pixel count of the 7D and essentially magnifying the reduced contrast with the 1.4x, that's probably causing the problem. My guess as to why the Tamron works is that the optical glass may not be as good as the Canon... just a thought.

My 1.4TC works well with the 500mm and produces sharp images on both my mkIV and 7D, both of which have been microadjusted with the convertor. I think there are two points to consider is the need to get the shutter speed up a bit as you are now effectively playing with a 700mm lens rather than a 500mm. The other is to reduce the aperature when using a teleconvertor which I find produes a better result, I usually aim for F7.1 as a starting point.

Here is a recent photo of skylark using the mkIV and 500mm with 1.4Tc handheld at ISO 400 F7.1 and 1/2000s

http://i89.photobucket.com/albums/k2...ylark20101.jpg

and a crop of the tail area off the raw file where you can see the setup is having no problem resolving detail. Apologies for the difference in colour I am having a few issues with colour balance with Caputre 5 which is tending to put a bit of a red cast on things.

http://i89.photobucket.com/albums/k2...ark20101-1.jpg

cheers

Rich

This image was taken with a 7D and the 4/500 + 1.4. No microadjustment. f5.6, ISO 200, 1/1250, tripod.
Imported into LR2 with standard settings. 100% crop exported with no adjustments and no output sharpening.
For a 100% crop I think this is ok. What do you think?

With the right post processing (e.g. some USM in CS4), this image will be very sharp.

I have noticed that the combination works pretty well (when you can get a short shutter speed). Quality is of course worse than without the 1.4x but not much. Stepping down to 7.1 as mentioned by Rich helps.

Markus

Well I am happy with the posts here and it shows that Chris and myself have a valid point, until Canon can fix it, no more 1.4TCs on my 7D.

And yes Canon CAN adjust the 1.4X TC IIs.

Quote:

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Originally Posted by Doug Brown

And here's the Caracara.

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Doug- Notice the shape of the highlight in the eye of the caracara. This has all the hallmarks of unstable air caused by heat and refraction. I have seen this many times now- you go out on a shoot and do what you have always done before and all the images are like you have shown. Of course you think it's you because there is nothing obvious to cause the problem.

Here's what I mean- this was a hot day on a local beach.

Frankly I think is common to underestimate the importance to IQ of good clean air between the lens and the subject.

Another day in the field with the Mark IV, the 500, and the Canon 1.4x. I'm happy to report that my problem was likely a poor connection between lens and TC (some Lens Coat had crept up to the edge of the 500). The combination worked flawlessly today after adjusting the neoprene. The 7D has also worked great with the 500 & 1.4x combination.

John beat me to it. Especially this time of year -- the sun is strong and the air is relatively cool and that can lead to nasty heat refraction. It should not be taken lightly. This commonly screws up images and this is the season for it in the northern hemisphere. It's best to photograph early in the morning before the sun's energy starts heating up the ground.

Now that most cameras offer video, it's a great way to see how bad heat shimmers can be.

Alan

Water vapour coming off vegetation also seems to play havoc with focusing and is another potential problem that shouldn't be underestimated.

Thanks Rich but I took that matter into consideration.:)