Query about IQ on focal length (FL) of 200mm and 300mm


Omahom

New Member
Dec 14, 2010
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#1
Hi bros, I have a query on cropping of photos taken from FL of 200mm and 270mm.
I recently took a photo of the moon from my Canon 70-200 F4 L lens (FL @ 200mm)and cropped the photo when doing PP.
The IQ was not as sharp compared to the same shot taken from the Tamron 18-270 PZD (FL @ 270mm), same cropped size as well.
Is it due to different FL despite the Canon being a 'superior' lens than the Tamron?
Or should I get the calibration done?
I am using the 550D body.
Thks!
 

Rashkae

Senior Member
Nov 28, 2005
19,105
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#2
200mm and 270mm will definitely have a noticeable difference. The longer focal length will result in the moon having a higher "magnification" on the sensor, thus giving the appearance that it's sharper.

Also, you should know that lenses are generally sharper when stopped down - the 70-200 would be sharper at f/5.6 or f/8 than at f/4.

Try shooting with the Tamron at 200mm, f/5.6 and the Canon at 200mm, f/5.6 and compare. That would be fairer.
 

Cowseye

Senior Member
Mar 7, 2010
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Singapore
www.ttlo-cowseye.com
#3
Rashkae said:
200mm and 270mm will definitely have a noticeable difference. The longer focal length will result in the moon having a higher "magnification" on the sensor, thus giving the appearance that it's sharper.

Also, you should know that lenses are generally sharper when stopped down - the 70-200 would be sharper at f/5.6 or f/8 than at f/4.

Try shooting with the Tamron at 200mm, f/5.6 and the Canon at 200mm, f/5.6 and compare. That would be fairer.
If I'm not wrong, I think the aperture has reached F/6.3 @ 200mm for tamron.
 

Omahom

New Member
Dec 14, 2010
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#4
Rashkae said:
200mm and 270mm will definitely have a noticeable difference. The longer focal length will result in the moon having a higher "magnification" on the sensor, thus giving the appearance that it's sharper.

Also, you should know that lenses are generally sharper when stopped down - the 70-200 would be sharper at f/5.6 or f/8 than at f/4.

Try shooting with the Tamron at 200mm, f/5.6 and the Canon at 200mm, f/5.6 and compare. That would be fairer.
Thks for the simple but vy clear explanation.. Much appreciated. Been trying to get it as sharp as the Tammy the whole night.. :)
 

Omahom

New Member
Dec 14, 2010
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#5
Cowseye said:
If I'm not wrong, I think the aperture has reached F/6.3 @ 200mm for tamron.
Not sure as I hv since sold the Tammy.. But at 270mm it's f6.3
 

Omahom

New Member
Dec 14, 2010
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#6
I am also aware that each lens hv their own 'sweet' spots. Meaning being IQ being sharpest at a particular f. I tried by taking a scene at different f but could not really tell the diff between f8-f16 for most of the Canon lens I own. From the collective experiences here, is there a better way to do this?
 

giantcanopy

Senior Member
Feb 11, 2007
6,232
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SG
#7
I am also aware that each lens hv their own 'sweet' spots. Meaning being IQ being sharpest at a particular f. I tried by taking a scene at different f but could not really tell the diff between f8-f16 for most of the Canon lens I own. From the collective experiences here, is there a better way to do this?
All i usually gather about sweet spot info from lens reviews and testings. I usually use the required aperture for my shots.
I guess if you really want, you can shoot a same scene with a wide variety of apertures and identify 100% pixel peep from there.

However the effects of the aperture is probably more important than fine print sharpness.

Ryan
 

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