Sharpness testing with Canon 50MM 1.8.....a bit weirb i think ?


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Arvin

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Jan 14, 2006
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After got my Canon 50mm 1.8, just today have time do some tests about the sharpness
of this lens.
Here the setting :
-The distance btw cam and object around 1.5 metre
- quality setting in cam : jpg super fine
- center point focus
- crop by ACDsee ver 7 ( centre point )
- save with best quality ( acdsee )
- no tripot but the cam put on table with self timer setting (cam keep still no movements)
- miss some description ?

The conclusion :
- Image more crisp and sharp at ISO 200 up at 1.8
- image more crisp at ISO 100 & 400 at 3.2 but blur at ISO200 ??? (2 times testing 1st more obvious)
- Images more crisp and sharp at ISO100 3.2 up ( but no other ISO testing)

I dont know does your lens like that also or my i have a badcopy ?
Any comments ?

( Forgive my bad English )


Cheers,

Caofei


First test at 1.8 (various ISO setting)
Resize full images


ISO 100 at 1.8 (crop from centre of above image)


ISO 200 at 1.8 (crop from centre of above image)


ISO 400 at 1.8 (crop from centre of above image)
 

Arvin

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Second test at 1.8 (various ISO setting)
Resize full images


ISO 100 at 1.8 (crop from centre of above image)


ISO 200 at 1.8 (crop from centre of above image)


ISO 400 at 1.8 (crop from centre of above image)
 

Arvin

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Jan 14, 2006
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Second test at 3.2 (various ISO setting)
Resize full images


ISO 100 at 3.2 (crop from centre of above image)


ISO 200 at 3.2 (crop from centre of above image)


ISO 400 at 3.2 (crop from centre of above image)
 

n0d3

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Feb 3, 2003
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You sure there isn't any camera shake? What I suspect is the higher the ISO you set, the faster the shutter speed and thus less blur due to shake.
 

Arvin

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n0d3 said:
You sure there isn't any camera shake? What I suspect is the higher the ISO you set, the faster the shutter speed and thus less blur due to shake.
Nope..even i scolded my kids not too close to the table.
Actually i have suspect there is some images problem at 1.8 on iso 100, once i take some pics with iso200, i have a feeling that images with the ISO 200 more crisp and sharp, thats make me want to test it out.

Cheers,
Caofei
 

Arvin

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Jan 14, 2006
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Even i tested twice at 1.8 with ISO 100,200,400
and the results above as a proof

Cheers,
Caofei
 

Hoky

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Arvin said:
Even i tested twice at 1.8 with ISO 100,200,400
and the results above as a proof

Cheers,
Caofei
Theoretically the ISO setting is the film sensitivity to light.
It should not have any effect on bokeh, sharpness of the lens... etc.
 

Arvin

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Jan 14, 2006
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Hoky said:
Theoretically the ISO setting is the film sensitivity to light.
It should not have any effect on bokeh, sharpness of the lens... etc.
Thats why i said abit weirb, i always thinks the ISO100 is the best interm of sharpness...

Cheers,
Caofei
( Just realised this member name belonged to my little brother, i have my own member named Caofei in this forum)
 

Hoky

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Arvin said:
Thats why i said abit weirb, i always thinks the ISO100 is the best interm of sharpness...

Cheers,
Caofei
( Just realised this member name belonged to my little brother, i have my own member named Caofei in this forum)
Digitally, lower ISO numbers purely gives you less grainy images (less sensitive to light as well). Doesn't affect sharpness.
Sharpness is obtained thru the lens with the good assistance of the photographer.

You should be having a relatively good copy from what I can see in some of the images.
I've got a bad copy Sigma lens recently and you can tell, it's crappy when you get one of those. Had it fixed up though but still ain't as perfect as what I expected.
 

Limsgp

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Dec 16, 2005
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Hi!

Some comments.

maybe you can consider re-doing the test, but take note of the following

With the camera in AF, press shutter halfway, let it focus, then set to manual (this prevents the AF from re-focusing and hence maybe result in different focus everytime you press the shutter).

The results should be more consistent at different ISO settings (e.g. all blur or all sharp).

Probably not relate to camera shake since you mentioned it is on timer mode. But when you press the shutter button the camera may "shift" a little and aim somewhere at the instant the shutter is pressed. Also, it may use different AF sensor out of the few available each time the pictures is taken if it is in full auto mode.

Somemore the subject distance is short, and the DOF could be only a few mm at so big aperture.



Regards


Arvin said:
Even i tested twice at 1.8 with ISO 100,200,400
and the results above as a proof

Cheers,
Caofei
 

Arvin

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Jan 14, 2006
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Thanks for u guys comments.
Oh..forgot to mention that all the pics, i took it with manual setting, was made sure that the center point get focus (the red flare sign), sometimes made me have to half press the shutter several times for ensure the center point get focus.

Cheers,
Caofei
 

Arvin

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Jan 14, 2006
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Maybe next time i use focus lock, what do you think.

Cheers,
Caofei
 

catchlights

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stick a page newpaper flat on the wall, and set you camera on tripod to do a test.

ISO will not affect sharpness, camera movement will.
 

Arvin

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The bad is i dont have a tripot to test...but put the cam on the table and set self timer setting at 10 secs does it make different when using tripot ? ( while the timer count down till the shoot finish, no other object neither my hand touch the table )

Cheers,
Caofei
 

catchlights

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Arvin said:
The bad is i dont have a tripot to test...but put the cam on the table and set self timer setting at 10 secs does it make different when using tripot ? ( while the timer count down till the shoot finish, no other object neither my hand touch the table )

Cheers,
Caofei
Your test already shows camera shake, when the mirror slam up and down, are your sure your camera will not move?
 

Arvin

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Ok as you said this method will couse the cam shake thus the image become blur, but did you notice the third test with 3.2 with ISO100 ? this pics shutter speed i think your must know is the shortest amongs all the pics i have taken, but this pics didint suffered from sharpness ?


Cheers,
Caofei
 

catchlights

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Arvin said:
Ok as you said this method will couse the cam shake thus the image become blur, but did you notice the third test with 3.2 with ISO100 ? this pics shutter speed i think your must know is the shortest amongs all the pics i have taken, but this pics didint suffered from sharpness ?


Cheers,
Caofei
the result of your test do not show anything.

1. are you certain that thru out the test, the focus, distant, does not change?
2. speed will not affect shapeness unless is too long.
3. a 50mm lens, of any brand of 35mm cameras, it suppose to be one of the sharpest lens, if your test can shows a 50mm lens is not sharp, out of 99% is something wrong with the test.
4. only one or two lens can offer sharp focus from corner to corner at wide open, but not this one.

Please do a google search of how to DIY lens test, I will not explain anymore.
 

Arvin

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Jan 14, 2006
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Thanks for the all you guys feedbacks, very apreaciate it
Firstly i want to make it clear, the intention of my test is want to find out if i have a badcopy or whats something wrongs with my test setting, thus i said a bit weirb.
About the focusing prob. i dont know if i have done it right : i just make sure when i half press the shutter button the red sign of the centre point have flare ; the distance btw cam and object did not change.

Cheers,
Caofei
 

Stoned

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Try a proper test again with tripod, mirror lock-up and cable/remote release. ISO does not affect sharpness at all.
 

jbma

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Dec 28, 2003
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I think you did not do the test properly. ISO should not affect the sharpness of the lens. Here's my suggestions

1. Use tripod
2. Place the newspaper flat on the wall
3. Focus and then lock focus
4. change the ISO and snap
5. Use mirror lock-up

It seem there is some camera shake.
 

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