Reply to thread

Message

<blockquote data-quote="WayneF" data-source="post: 218106" data-attributes="member: 12496">Right, that is normal for all macro lenses, when focused close to macro distances.&nbsp; Your other lenses do not do this, because they cannot focus to macro distances.&nbsp; But to focus closer, the lens has to be extended, which is longer focal length.&nbsp; f/stop is focal length / aperture diameter, so for the same diameter, the f/stop number increases from what is marked. This is minor and not noticeable at normal near distances, but technically 1:1 magnification macro is 2 stops different than marked.&nbsp; However, some lens designs are less symmetrical, and may not be exactly 2 stops at 1:1, but still same ballpark.Through the lens metering will still get it right.Since the macro lenses do focus to 1:1, their design takes pains to show the actual modified f/stop number.&nbsp; Whereas normal lenses focusing to 2 feet do shift slightly, but there is no concern to show this.&nbsp; It is only minor then.&nbsp; But the macro lens does show that too.We don't use f/2.8 for 1:1 macro of course, but this means&nbsp; without this compensation feature, that when you set f/16, it changes to f/32 (at 1:1).&nbsp; A handheld light meter would seriously be wrong then.&nbsp; Except now the lens shows the true adjusted value, so if you set f/16, it is really is f/16, and the hand held meter can get it right.</blockquote>

[QUOTE="WayneF, post: 218106, member: 12496"] Right, that is normal for all macro lenses, when focused close to macro distances. Your other lenses do not do this, because they cannot focus to macro distances. But to focus closer, the lens has to be extended, which is longer focal length. f/stop is focal length / aperture diameter, so for the same diameter, the f/stop number increases from what is marked. This is minor and not noticeable at normal near distances, but technically 1:1 magnification macro is 2 stops different than marked. However, some lens designs are less symmetrical, and may not be exactly 2 stops at 1:1, but still same ballpark. Through the lens metering will still get it right. Since the macro lenses do focus to 1:1, their design takes pains to show the actual modified f/stop number. Whereas normal lenses focusing to 2 feet do shift slightly, but there is no concern to show this. It is only minor then. But the macro lens does show that too. We don't use f/2.8 for 1:1 macro of course, but this means without this compensation feature, that when you set f/16, it changes to f/32 (at 1:1). A handheld light meter would seriously be wrong then. Except now the lens shows the true adjusted value, so if you set f/16, it is really is f/16, and the hand held meter can get it right. [/QUOTE]

Verification