DA 70mm vs FA 77mm Limited

Image Quality: Sharpness

For sharpness testing, we used an Edmund Resolution Power Chart as well as field tests. A sample of the chart is seen below. The chart was originally designed to determine the maximum resolving power of an optical instrument. We’re not using the chart as it was originally intended, which was to distinguish the last group of visual lines to be discriminated. The purpose of using the chart is to compare one lens to the other. The chart allows the viewer an apple to apple comparison of different lenses using a standard measurement.

Lens test chart

Sharpness Test

For the field sharpness testing, we selected a fountain that has fine details that allow for a detailed examination. The camera was placed on a tripod to minimize changing either the camera location or settings.

Fountain

Outside Sharpness Test Crop

Conclusion

The results of the lens test chart were very interesting in that the difference between the two lenses was so minor. The FA 77mm was sharper at F1.8 than the DA 70 at F2.4. The FA continued to hold the advantage until it reached f5.6 and then the lenses were nearly identical in their resolution. The field sharpness test, which is perhaps more valuable, indicated that the lenses were almost impossible to differentiate. One interesting note was the difference in color rendition of the two lenses. It is easier to see that in the bokeh example.


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