I have learned a cool new trick; how to take screen shots on my computer. Today I did an experiment to compare the sharpness of images captured using the centre versus one of the outer focal points on my camera. I have pretty much stopped using the outer points because I felt that they just weren't getting the job done. It is a bit of a pain not using them though so I was keen to take a closer look.
These pictures are SOOC with no editing. I have zoomed in on the eyes for each image to get a better idea of how much sharpness was achieved. I used the Tamron 24-70mm set at 50mm.
First up we have Rexy in the desirable rule of thirds composition. To achieve this without having to focus and recompose I used the outer focal point. It sat right on top of the eye closest to us and neither of us moved a muscle. The image doesn't look too bad from a distance, but when you zoom in... yikes! It was at a good shutter speed too so there shouldn't be any camera shake or motion blur. It was a high ISO so of course noise is a factor here.
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| Outer focal point - f/2.8; 1/160; ISO 1600 |
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| Outer focal point - f/2.8; 1/160; ISO 1600 |
However, look what is achieved at the same settings but using a centre focus. I didn't recompose as I wanted to compare the focal points alone. The eyes are so much clearer!
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| Centre focal point - f/2.8; 1/160; ISO 1600 |
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| Centre focal point - f/2.8; 1/160; ISO 1600 |
I wanted to see what would happen if I lowered the ISO to reduce some of the pesky noise. Again I started with the outer focal point but this time the ISO was 400. This meant that I had to drop the shutter speed to 1/30. The result... not good!
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| Outer focal point - f/2.8; 1/30; ISO 400 |
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| Outer focal point - f/2.8; 1/30; ISO 400 |
I tried again using the centre focal point and .... wow! I can't believe how much sharper it is given the low shutter speed.
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| Centre focal point - f/2.8; 1/30; ISO 400 |
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| Centre focal point - f/2.8; 1/30; ISO 400 |
Just for kicks, I decided to go even lower. I took the ISO down to 100 and the shutter speed to 1/13. The outer focal point was disastrous. There must be some motion blur and camera shake setting in now.
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| Outer focal point - f/2.8; 1/13; ISO 100 |
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| Outer focal point - f/2.8; 1/13; ISO 100 |
Even so, the centre focal point managed to capture a reasonably sharp image even at those settings. My Tamron lens is amazing though. There is no way I could have achieved that with the 50mm f/1.8.
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| Centre focal point - f/2.8; 1/13; ISO 100 |
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| Centre focal point - f/2.8; 1/13; ISO 100 |
After my fun little experiment I have to conclude that I cannot use the outer focal points at all. The results are so much worse than using the centre focal point. It is disappointing and I can only hope that things will get better when I can upgrade my camera in the (long term) future. In the mean time I am left with compositions that I don't want or using focus recompose. This can be hugely challenging when the kids are bouncing around. I need to be able to focus and click almost simultaneously. It also means that I lose much of the benefit of back button focus. Very frustrating.
Speaking of frustrating and bouncing around, we got the trampoline out today. The bouncing was fun, if a little difficult to capture. The frustrating part is white balance in this room. The images still look a tad warm to me but the skin tones are supposedly "correct". I am starting to think that it is the wall colour that is the problem.
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