I am going to Panama at the end of next month, and want everything in top order before leaving.
As the weather over here in Switzerland has been pretty gloomy ever since I got my 7D I have not had much chance to really test it outside with birds in decent light. So therefore, I wanted to run through the microadjust with the few lenses I will be taking with me (due to weight restrictions on domestic flights that will be 50mm f1.8, 100mm macro, 300mm f4 + 1.4TC). I have a few questions concerning the experiences people have had with this and methods.
- Do people prefer a printed target and comparison of multiple images post hoc or the moire interference method on screen?
- If it is the multiple image method I assume one shoots in Fine JPEG to speed up the process?
- It is suggested that the distance away from the target is 50 times focal length. Is this absolutely necessary? It would be no problem with the 50 or 100mm, but even though my longest focal length is not monstrous (300 + 1.4 TC) my house does not have such a long hallway.
Thanks for any help on this and any other advice that you may have. I know there are many articles out there on microadjust, but they all seem to use different setups, so I thought I would ask I group I can trust.
I believe it is the most accurate to do. The instructions say to perform the adjustment at 50 times the focal length. However, some say to do it at the distance you mostly shoot. I have done both and not found a difference.
Some hints are that even though the article is on the MK3 it applies to all cameras with the adjustment feature and also Live View. You should also ensure you have zero exposure compensation. The LV screen needs to be able to show all tonal ranges. Once I forgot I had +1 dialed in and could not visualize the diffraction pattern.
I would also check the results a few times. All in all a great way to do this adjustment.
Ed, I tried your suggestion on the 50mm before going into work this morning. The principle seemed to work well and it seems to have been back focusing by 10. I will recheck the 50mm again when I am home tonight to make sure it is repeatable, and run the test with the 100mm.
For the 300mm and 300mm + 1.4TC I am going to have to bring my setup into work. That is the only place where I am going to be able to get sufficient distance between myself and the computer screen.
I have just been working on the calibration for the Mark IV the last two days. I tried the moire pattern method and just don't find it that exacting. The lens align looks to be a perfect solution but you could spend up to 300 dollars for the one with the long ruler. I used the target that you set on a 45 degree angle for right now and like this method the best. The trick is that you must get the target at the exact angle of 45 dgrees and square to the lens-camera as possible. On my 600 after performing ten shots per adjustment value it was entirely clear that at -9 I would be ever so slightly back focsed and at -10 I would be ever so slightly front focused. I'm choosing -9 as I feel a little BF is okay and even desirable. And I have also been considering that when photographing BIF usually the front focused part of the DOF is wasted on thin air so it might be desirable to put a setting in(temporarily for that shot) that would intentionally BF and thereby capture more of the bird in focus than what would be otherwise a possibility. Especially when you shooting at a large aperture opening trying to keep your BG blur under control.
The targtet I'm using is the one by Tim Jackson. I used a draftsman 45-square and a small laser level and 2 inch tape over the end of the lens shade with an X at the exact middle on it to precisely line up the target to the camera-lens. 25X your focal length should be sufficient. Keep in mind this distance suggestion has a lot to do with the exact ammount of DOF on either side of focus point and how that ratio varies from distance to subject and to lens used. It sould be averaged for the actual distances at which your shooting usually--but that is meaningless for most people here I would think. Maybe studios would shoot consistantly at a certain distance.
By the by--the Mark IV nailed such consistant readings in the test shots that sometimes I couldn't see a change when flipping through them using cntrl tab viewing the ten shots with the same adjustment value. The consistancy was like I have never seen before. Gave me great confidence in my final readings for the setting in micro adjust.
Chuck Westfall, Canon Technical Services Advisor, does not recommend using targets that are angled to the sensor plane. He states in his writings, that angled targets will produce inaccurate results.
Do not attempt to autofocus on an angled chart, because doing so will degrade the consistency of the camera's focusing measurement. Keep in mind that the camera's AF sensor is comprised of multiple pairs of linear pixel arrays. If you attempt to autofocus on a single line in an angled focusing chart, only a few pixels from each active pixel array will "see" the target. Ideally, the contrast in the reference target should cover the entire area of the camera's center focusing point, and the reference target should be perfectly parallel to the camera's focal plane. - Chuck Westfall, December, 2008 The Digital Journalist
7D microadjust questions
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