Differences

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--- doc:appunti:hardware:olympus-e-m10:pergear_fisheye [2022/12/17 17:30] – [The Pergear 7.5mm F2.8 Fish-Eye] niccolo
+++ doc:appunti:hardware:olympus-e-m10:pergear_fisheye [2022/12/20 09:40] (current) – [Lens-flare] niccolo
@@ Line 1: / Line 1: @@
 ====== The Pergear 7.5mm F2.8 Fish-Eye ======
-**Obiettivo manuale fish-eye con la Olympus E-M10 Mark II**
+**Obiettivo manuale fish-eye su Olympus E-M10 Mark II**
 ^ Specifications  ^^
-| Focal length   | 7.5 mm  |
+| Focal length         | 7.5 mm           |
-| Angle of view  | 130° (on MFT)  |
+| Angle of view        | 130° (on MFT)    |
-| Aperture range  | f/2.8 - f/22  |
+| Aperture range       | f/2.8 - f/22     |
-| Focus range  | 12 cm - ∞  |
+| Focus range          | 12 cm - ∞        |
-| External dimensions  | ø61 mm x54 mm  |
+| External dimensions  | ø 61 mm x 54 mm  |
 | Weight (excluding caps and hoods)  | 320 g  |
-The specifications above are provided by the manufacturer and are quite approximative; checking with many on-line field of view calculators (you can try this one at [[https://www.scantips.com/lights/fieldofview.html|www.scantips.com]]), the angle of view for a 7.5 mm lens on a Micro Four Thirds sensor should be 98.15°. I made some measures on the field and it turned out that the actual **horizontal field of view** is about **107°**, which means a lens of about **6.5 mm** focal lenght mounted on a Micro Four Thirds system.
+The specifications above are provided by the manufacturer and are quite approximative; checking with the various on-line field-of-view calculators (you can try this one at [[https://www.scantips.com/lights/fieldofview.html|www.scantips.com]]), the angle of view for a 7.5 mm lens on a Micro Four Thirds sensor should be 98.15°. I made some measures on the field and it turned out that the actual **horizontal field of view** is about **107°** which, on a Micro Four Thirds system, is equivalent to a lens of **6.5 mm** focal lenght.
@@ Line 45: / Line 45: @@
 {{pergear-sun-flares.jpg?360|Lens-flare ed effetto stella contro sole}}
 {{pergear-light-flares.jpg?360|Lens-flare ed effetto stella con faretto alogeno}}
+===== Aberrazione cromatica =====
+Una lente in generale può essere affetta da due tipi di [[wp>Chromatic_aberration|aberrazione cromatica]], assiale e laterale (o trasversale):
+  * **Axial chromatic aberration**: different wavelengths of light are focused at different distances from the lens.
+    * Typical at long focal lengths.
+    * Occurs throughout the image.
+    * It is reduced by stopping down (due the augmented depth of field).
+    * Difficult to remedy in post-processing.
+  * **Transverse chromatic aberration**: different wavelengths are focused at different positions in the focal plane.
+    * Typical at short focal lengths.
+    * Increases towards the edge.
+    * Tt is not affected by stopping down.
+    * Can be corrected by radially scaling the RGB planes appropriately so they line up.
+FIXME: Vediamo quanto incide l'aberrazione cromatica laterale e quanto è possibile correggerla in postproduzione.
 ===== Third party lens manufacturer =====