Hopper/unknown/ladybird macros

P_T · Post by **P_T** » Mon Nov 03, 2008 5:43 am

Moonwalking Hopper, this bug walked backwards.

Full size
http://farm4.static.flickr.com/3251/293 ... fccd_o.jpg

Orange looking bug sipping on a tree branch. Be great if you can ID it.

Full size
http://farm4.static.flickr.com/3047/296 ... b401_o.jpg

Another attempt at Steelblue Ladybird.

Full size
http://farm4.static.flickr.com/3071/291 ... 85f7_o.jpg

Thanks for looking!!

Harold Gough · Post by **Harold Gough** » Mon Nov 03, 2008 7:47 am

Excellent, although my personal preference is for more DOF from a couple of stops smaller.

Harold

P_T · Post by **P_T** » Mon Nov 03, 2008 7:52 am

Thank you Harold. The first two were shot using f/11 and the last one f/13. I think it's more my own beginner mistake for not utilising the plane of focus more effectively.

Harold Gough · Post by **Harold Gough** » Mon Nov 03, 2008 8:04 am

You should have been OK with the middle one but I would have gone for at least (at largest) f16 for the blue one.

One difference with DOF at such magnifications is that it is much the same behind and in front of the subject. (At lower magnifications it is much greater to very much greater behind).

Harold

rjlittlefield · Post by **rjlittlefield** » Mon Nov 03, 2008 9:18 am

One caution about stopping down farther: diffraction blur.

That lady beetle is maybe 2X onto the sensor. At 2X, marked f/13 is more like effective f/39. Marked f/16 would be effective f/48, and so on -- way too small an aperture to be sharp. When I take a look at the "full size" version at http://farm4.static.flickr.com/3071/291 ... 85f7_o.jpg , it already looks a bit soft, and it's only 814 x 1024.

I think you made a good choice, P_T. Stopping down farther would not have exposed much more detail in areas that are now OOF, and it would have softened even farther areas that are now fairly sharp.

--Rik

Ken Ramos · Post by **Ken Ramos** » Mon Nov 03, 2008 3:51 pm

Well the math is over my head

but the images aren't. Those are really nice there P_T

Especially the second and third!

Harold Gough · Post by **Harold Gough** » Tue Nov 04, 2008 12:39 am

I would normally use a high quality x2 teleconverter to get the extra stop without closing down and thus doubling the magnification at the same working distance.

Harold

rjlittlefield · Post by **rjlittlefield** » Tue Nov 04, 2008 1:27 am

Yes, this is a win for working distance. But inserting a 2X teleconverter also doubles the effective f-number, very much like extending the lens to get the same magnification. There's no free lunch -- the tradeoff between DOF and diffraction blur is the same no matter how you get the magnification.

--Rik

Harold Gough · Post by **Harold Gough** » Tue Nov 04, 2008 1:43 am

Rik,

That's why I use a converter!

On the matter of diffraction in lenses in general, I have always understood that the concern is about that arising from the edges of the diaphragm. As you close down to a smaller and smaller aperture, that part of the image with the worst of the diffraction effects contributes an incrementally increasing proportion of the image. I don't see how that can be increased by using a teleconverter, which uses the part of the image furthest from the diaphragm.

Harold

rjlittlefield · Post by **rjlittlefield** » Tue Nov 04, 2008 2:29 am

Harold Gough wrote:On the matter of diffraction in lenses in general, I have always understood that the concern is about that arising from the edges of the diaphragm.

That understanding is not correct.

The edges of the diaphragm really have no significant effect.

What matters is that the aperture restricts the maximum angle between light rays, which in turn restricts their ability to interfere with each other to produce differences in intensity that the sensor can detect.

Graham Stabler and I had a long discussion about this some months ago. The discussion is hard to follow, and then takes off on another point, but take a look at the illustration at http://www.photomacrography.net/forum/v ... 0&start=47 .

The point is that light rays striking the sensor at relatively steep angles with respect to each other can interact to form fine patterns of intensity, while light rays striking the sensor at narrower angles can only form coarser patterns.

DOF depends on the same angles, hence my comment that there is no free lunch -- the tradeoff between DOF and sharpness is the same no matter how you get the magnification. The nominal setting of the lens to get a particular DOF/sharpness will vary depending on whether you use extension or a teleconverter, but the combination of DOF and sharpness will not.

--Rik

Harold Gough · Post by **Harold Gough** » Tue Nov 04, 2008 4:58 am

I'm not sure that all this information about interference has much to do with diffraction, the latter being about change of direction, in which scattering would be included.

Harold

rjlittlefield · Post by **rjlittlefield** » Tue Nov 04, 2008 3:31 pm

Harold, I started a separate topic to continue this discussion.

See What really causes "diffraction blur"?, in the Technical Discussions forum.

--Rik