Definition of sharpness


Sep 12, 2005
129
0
16
Sembawang
#1
Hi all,

I am a newbie to photography, would like to check with the senior of CS how would you define sharpness. I have got a sigma 30mm f1.4 and canon 17-55mm f2.8 on my 60d. However after I took a pic with both lens at 30mm and 35mm each at f8. It look the same but upon 100% crop, sigma is loosing so much detail as compare to canon lens.

I have bring my sigma for calibration and the engineer mention it is already calibrated. I would like to know if I am expecting too much from sigma 30mm as compare to the king of crop. How does everyone define sharpness? My friend used to tell me at 50% crop have details is already at the best but I some how is not convince. Hope to get your advice.
 

rhino123

Moderator
Staff member
Sep 1, 2006
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NA
#2
Hi all,

I am a newbie to photography, would like to check with the senior of CS how would you define sharpness. I have got a sigma 30mm f1.4 and canon 17-55mm f2.8 on my 60d. However after I took a pic with both lens at 30mm and 35mm each at f8. It look the same but upon 100% crop, sigma is loosing so much detail as compare to canon lens.

I have bring my sigma for calibration and the engineer mention it is already calibrated. I would like to know if I am expecting too much from sigma 30mm as compare to the king of crop. How does everyone define sharpness? My friend used to tell me at 50% crop have details is already at the best but I some how is not convince. Hope to get your advice.
How to you conduct your test? Handheld or on tripod? What is the shooting condition, what is the exif?

Note that the Canon lens that you mentioned had IS while Sigma's 30mm didn't have.

A photo with exif information would tell a lot.
 

TWmilkteaTW

Senior Member
May 30, 2011
2,251
1
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#3
To answer your question.. i have no idea too..im confused myself. Sometime as well..in a good light..my 2k++ lens is producing similar pic quality compared to a 18-55 kit lens. (Image quality is only better IF U CROP/Pixel Peep at 50%/100%). Things that really put them apart are..the quality of bokeh and flare control/distortion)
Color slightly more accurate too.

end of the day..you dont expect a $2000 lens to perform 4 times better than a $500 lens. (which is logical..and applies to many other things as well..)
 

Last edited:
Sep 12, 2005
129
0
16
Sembawang
#4
Hi all,

All test are done on a tripod with in door lighting. For 17-55mm it produce detail like the texture of the object will sigma 30mm with the same setting can't. Just want to confirm I am not expecting too much.
 

daredevil123

Moderator
Staff member
Oct 25, 2005
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lil red dot
#5
Why don't you post those test pictures here? So the nice and friend folks here can advise accordingly?
 

Nashaz

New Member
Jul 26, 2010
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#7
Just because the technician says its calibrated does not mean its calibrated properly. I myself had the same experience with my 50 1.4. However, there is some notable improvement after sending it to the sigma service center, the lens tended to jitter forwards and backwards when using ai servo on a stationary object. But after it came back, the jittering was reduced significantly. I suspect they might have done a firmware update on the chip inside the lens, updating its af algorithms rather then a physical calibration to the body as compared to canon's calibrations.

However, upon putting the lens to calibration charts it was very apparent that it was backfocusing at close distances and i had to manually key in -10 in the af settings. After that the AF was spot on and at F2 it was tack sharp that 100% crops on my 5d2 and 3 were completely usable as full blowups. At 2.8 it was even sharper then most of my canon L lenses.

Just one thing to note, fast primes are used primarily for its large large apertures and shallow depth of field. They may not be the sharpest when compared to some of the other "slower" primes, fast zooms or when stopped down. But in the absolute of things, the sigma 30 is already very sharp for a fast prime. Try comparing the 2 lenses at different apertures. Shoot from wide open for both and stop down maybe 3-4 stops and compare the shots. Check for any misfocusing by using af charts that can be easily downloaded from the web.
 

Sep 12, 2005
129
0
16
Sembawang
#8
Hi nashaz,

Thanks for the advice. I did a very simple focusing test. I lay 3 engezier battery across the table in a 45degree manners with each 1.5cm apart. I place my 60d on the tripod about a mentor from the subject. I shot with my 17-55mm at f2.8 at around 30mm focal length using center focus point on the middle battery and it is tack sharp and the other two battery which one is slightly in front and the other slightly behind the center battery is oof.

The same test is repeat for sigma 30mm f1.4 at f1.4. The end result is that the battery in the front tends to be slightly more sharp than the centre battery even though I am focusing at the center battery. However at 100% crop without pp. I still feel it is overall soft. I denote that the lens is having some front focus issue. The ca is also quite bad which result in the overall image even more soft. Since I got this lens as the second owners from CS forum I never got a tact sharp image at 100% crop. This is making me loosing a lot of faith in getting sigma lens. I have been holding back the 50mm f1.4 which I find it useful or half bod portrait shot. Maybe my expectation for tact sharp is too high. But then again the 17-55mm met my standard. Really lost.
 

simonsng

New Member
Jan 29, 2003
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#9
enghwee

have you shot the 30mm at anything above f1.4? for it it be front or back focus, the front or the back portion where you are focusing has to be sharp. If it is the case, then you should send it back to sigma to have it checked. Stop pixel peeping, not like you going to print blow ups of A1 size for your photo.
 

Sep 12, 2005
129
0
16
Sembawang
#11
Hi simon,

Tried f1.4, f2, f2.8, f4, all the same. It is not tact sharp but the front battery is obviously more sharp than the centre battery that I am focusing on. Heard review in CS that sigma 30mm f1.4 is quite sharp but then quite disappointing.
 

sinned79

Senior Member
Jun 18, 2009
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www.aboutlove.sg
#12
Hi simon,

Tried f1.4, f2, f2.8, f4, all the same. It is not tact sharp but the front battery is obviously more sharp than the centre battery that I am focusing on. Heard review in CS that sigma 30mm f1.4 is quite sharp but then quite disappointing.
let me repeat again. post your photos here. else no one here can comment anything. its like talking discussing war on paper.
 

oceanpriest

Senior Member
Apr 24, 2010
3,455
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Ghim Moh
#13
let me repeat again. post your photos here. else no one here can comment anything. its like talking discussing war on paper.
Perhaps his test subject is NSFW one. So can't post in public :bsmilie:
 

Sep 12, 2005
129
0
16
Sembawang
#14
Hi there,

I redid the test today with the NSFW enegizer batteries again;) .

Below are the test environment

Lighting: Normal Room lighting
Distance of object from focal plane: around 560MM
Camera: Canon 60D
Lens: Sigma 30MM f1.4
Mode: AV
Aperture used: f1.4 - f5.6 @ 1/3 increment
Focusing point used: Center focus point only
File type: jpeg
Color Space used: Adobe RGB
Framing: Subject place at the center of the frame

Subject:3 Engeziser AA Batteries arrange at 45degree with 1.5CM apart
Focusing area: at the + and | sign of the center battery

Crop: 100% crop using Photoshop save at JPEG @ 100% quality

Link to my photo set in flickr
Sigma 30MM F1.4 Test shot with Canon 60D 100% Crop - a set on Flickr

Hope to clear some light.
 

Sep 12, 2005
129
0
16
Sembawang
#15
Oh Forget to add, all are shot at ISO 100 with timer 2 sec countdown on tripod and auto white balance.
 

mccm33

New Member
Apr 21, 2007
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#16
TS must have pawned by sigma 30mm f1.4 har ?

trade the lens away,case close.
 

daredevil123

Moderator
Staff member
Oct 25, 2005
21,657
68
48
lil red dot
#17
Your 30/1.4 looks like it has some issues. You might want to bring it in to Sigma Service center to get it checked out.
 

TWmilkteaTW

Senior Member
May 30, 2011
2,251
1
0
#18
According to the pic..and what i can see..at F1.6..it does show front focus problem..then at F1.4 its not say sharp..center and front look the same..
 

Sep 12, 2005
129
0
16
Sembawang
#19
Bring back to Sigma service centre today. From f1.4 to f2.2, it shows front focus. F2.5 to 3.5 it back focus and then at F4 to f5.6 front focus again. Dame piss. Told the engineer about the inconsistency. He mention he recalibrate it for free and just bring back. Going to do the same test again. Anyone have the same issue with sigma 50mm f1.4 before. Between canon and sigma which one should I go?
 

daredevil123

Moderator
Staff member
Oct 25, 2005
21,657
68
48
lil red dot
#20
Bring back to Sigma service centre today. From f1.4 to f2.2, it shows front focus. F2.5 to 3.5 it back focus and then at F4 to f5.6 front focus again. Dame piss. Told the engineer about the inconsistency. He mention he recalibrate it for free and just bring back. Going to do the same test again. Anyone have the same issue with sigma 50mm f1.4 before. Between canon and sigma which one should I go?
Actually, I saw the pic was just full of blur and flare at wider apertures. It is not just something as simple as front of back focusing.

My copy of 50/1.4 has no issues and is tack sharp.
 

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