What am I doing wrong?


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G-man

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Mar 2, 2006
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#1
Hi everyone,

I was trying out my lens at 70mm earlier on and here're 2 100% crops of the same image, one taken in Manual focus & the other in Autofocus. Much as my MF skills are subpar, I've been trying and somehow the MF results are always alot less sharp than the AF shots.

Can someone tell me what I'm doing wrong? I generally turn the focus ring till the image looks sharp on the viewfinder then take the shot, which has often worked pretty well for me in film SLR on my old Nikon. Using the Canon EOS 350D, I cannot seem to master the MF mode at all without looking like the focus was just the wee bit off.

Can someone advise me please?

Thanks in advance


Autofocus at 70mm


Manual focus at 70mm

Note how the MF mode seems to produce slightly blurrer results even at identical settings for both the aperture, ISO and shutter speed?

In case it helps, the lens I was using was the Sigma 17-70mm, at 70mm, f/4.5, 1/5 second mounted on a tripod and ISO 100. Cam was a Canon EOS 350D

Would appreciate any pointers from the pros on how to improve my manual focus technique. Presently, it's turning the focus ring till the image is sharp in the viewfinder, then turn a little more then turn back to where the whole image was sharp again, especially the area where I wish to focus on.

Many thanks in advance.
 

denniskee

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Oct 26, 2003
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#2
1st, pls do not post in critique corner for this type of technical question. you can post this thread under "general, review, tech talk".

now below is my suggestion.

1) i thinks 1/5sec is too slow to stop motion blurr, more so if the subject is close to the camera.

2) unless you have change the orginal foucsing in you camera (DSLR and SLR alike) to "manual focusing screen", it is not likely to have a high success rate in doing manual focusing. more so if the subject is close to the camera as the dov is very shallow.

3) modern day auto focus lenses have very short throw from min focusing distant to infinity (my canon EF lens 50mm f1.8 is about 80deg turn end to end, vs my takuma 50mm f1.4 manual focusing lens is aboput 200deg turn end to end.), this is to improve the focusing speed (logicaly, you will use AF more than 90% of the time). hence the camera and lens electronics are design to handle this much more accurately than human hands and eyes.

4) i suggest you pump up the iso, use smaller aperture to get more dov and increase the shutter speed, while still under-expose by 1stop, than do ps-ing.

5) or use smaller aperture to get more dov. set to at least 1/60, bounce flash.
 

G-man

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#3
Thanks for the suggestion. I'll post in review,tech talk in future. :)

Thanks once again for your tips too.:thumbsup:
 

Splutter

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#4
1 more pt, do make sure that ur focusing screen is in focus. Meaning that ur diopter has to be set correctly. To check, unmount lens, face the cam to a white wall and turn the diopter until the AF points etched on the focusing screen are the sharpest.
 

G-man

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#8
denniskee said:
but he say mounted on tripod liao lay.
Yes it's still possible to have camera shake, due to mirror slap as I did not use a remote release.
 

ortega

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#9
denniskee said:
but he say mounted on tripod liao lay.
notice the highlights in the eyes, can see 2 highlights or not
def camera shake

i'd suggest trying again in bright daylight, also easier to focus because the viewfinder also very bright.

Also film slr have bigger viewfinder - easier to see and thus focus.
 

G-man

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#10
Ortega, thanks for the information.

Hey maybe it's not camera shake, maybe it's fat boy shake! :bsmilie: :bsmilie:
 

raptor84

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#11
When you relase the shutter for low speeds you might need to do a morror lock up or timed release. Either that or time your shutter squeeze (gently) with your breating :D Both pics do look a little under ot me as well.
 

G-man

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Mar 2, 2006
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#12
Raptor84, yea makes sense. Didn't think of using the mirror lockup. In any case, the exposure was under, probably due to poor lighting and my desire to quickly take the shot. Will be working on those areas too.

Well, I managed to take a few decent shots today and will be posting 1 up later in the relevant section.

Thanks everyone for all your tips.:thumbsup: :thumbsup: :thumbsup:
 

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#13
Tripod might be too flimsy, try using a remote or timer..

Or the cat might just be moving :dunno:
 

Stoned

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#14
if you really really love MF, for some odd reason, then you might want to change your focusing screen to a split screen one.
 

Leinaj

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#15
how did u get the cat to pose in the exact same pose for both takes :p prolly explains the "handshake", it could be the cat slight adjustment itself.

Given the same light conditions and considering the other suggestions like checking on your diopter is in focus, try f4.5 ISO 400 to allow for faster shutterspeed. .....
 

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