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Articles Table of Contents   Page 1: Introduction Page 2: Build quality and ergonomics Page 3: Operation Page 4: Bokeh Page 5: Examples—40/4 Page 6: Examples—80/2.8 Page 7: Examples—120/4 Page 8: Resolution and Diffraction Page 9: Resolution chart—40/4 Page 10: Resolution chart—80/2.8 Page 11: Resolution chart—120/4 Page 12: Stitching with the 40/4 Page 13: Field shot aperture series crops—40/4 Page 14: Field shot aperture series crops—80/2.8 Page 15: Field shot aperture series crops—120/4 Page 16: MTF for Hartblei 40mm f/4 Page 17: MTF for Hartblei 80mm f/2.8 Page 18: MTF for Hartblei 120mm f/4 Page 19: Conclusions

Resolution chart—80/2.8

Introduction

The MTF charts suggest that sharpness will be degraded by field curvature and astigmatism for the Hartblei 40/4 and 80/2.8, but not much by the 120/4.

Please see test notes on the 40/4 page.

Resolution chart

Results here are similar to those from the 40/4 in terms of contrast/sharpness and field curvature.

Contrast at f/2.8 is quite low, and it should be avoided except for a dreamy effect; the effect is similar to that seen with DSLR 50mm f/1.4 lenses, and might indicate spherical aberration (and therefore possible focus shift, though the image crisps up nicely at f/4).

The results show that with a flat (planar) subject:

• unshifted performance is excellent over most of the 35mm frame, slightly weak at the far corners until f/8 (astigmatism);
• fully shifted, the corner and center cannot be sharp at the same time unless the lens is stopped down to the f/11 - f/16 range;
• some trace uncorrected chromatic aberration is present;
• fully shifted, contrast is low in the corners (due to field curvature) unless focus is near the corner;
• astigmatism is unavoidable; even optimal focus for the corner does not avoid it;
• Overall best results near f/16; stopping down to f/22 degrades contrast and resolution substantially.
• field curvature comes into play significantly at about 5mm of shift; the last 5mm of shift is where the field curvature really is seen as a problem (for planar subjects).

Conclusions

Shifted performance on flat (planar) subjects reveals field curvature and associated astigmatism beyond about 5mm of shift, for which stopping down to f/11 - f/16 is strongly advised. For 3D subjects such considerations may be safely ignored.