I recently dusted off my Sigma 30mm f1.4 lens that I had been using with my Canon 40D. Once I upgraded to the 5D I figured that setup became redundant because I could achieve the same (except better) result with the full frame camera and the 50mm f1.4. I was right.
Then my “40D Walking Around 17-85mm” broke so I unretired the 30. I found myself in situations where I wanted to bring a DSLR but really didn’t feel like carting along the tool that buys my kid new shoes. Not that I would be thrilled if somebody spilled punch on my 40D but it wouldn’t be nearly as drastic.
So with that epic backstory behind us I decided to shoot a quick test comparing the 30mm on a crop vs the 50mm on a full. Buckle your seatbelts, here we go.
I tried to shoot both photos from the same angle and distance as best I could. Both cameras have identical settings but you can see slightly different exposure/colour results.
The first set was shot at f2.8 with the focus being set on one of the leaves of the tree on the beige t-shirt. Aide from the slight framing differences (I based framing on the focal points in the viewfinder. Turns out they are not identically placed in each camera…..) the images dont look wildly different to me. I would suggest there are subtle differences in the DOF as evidenced by the lettering on the beige t-shirt but if these weren’t viewed side by side I think you would be hard pressed to distinguish.
Where we do notice the difference is in the shape of the suitcase. Because we are using a wider angle lens to achieve the same framing as a standard 50mm lens, our perspective changes slightly. This results in the slight distortion of the suitcase. Once again I feel that if these photos were viewed independently nobody would complain about the warped suitcase, but when shooting a close up portrait of someone we might not be doing them any favours.
Next, I moved in slightly and cranked both lenses wide open to f1.4. In this case the focus is on the “A” in nature. This comparison illustrates the subtle difference in the shallow DOF.
I much prefer the image from the 5D but only when compared side by side.
Conclusion? This test confirms my earlier assessment that full frame is awesome and I recommend getting one if you can get it to pay your bills. If not, go with the crop sensor. You’ll save a few Deutschemarks and the chicks will still dig you.