Fine hairy details with aperture value f/5.6

[MacroLuv]

Paradoxically (or maybe not ) I hit the right DOF placement and focus more often with bigger apreture values (which gives smaller DOF range) than with smaller apreture values (which gives greater DOF range). Or it could be just because of shutter speed - my equipment doesn't include the tripod yet.
#1 - handheld, uncut - original full frame
#2 & #3 - crops from #1 - you can see very small hairs on the tail and thorax.



Model Canon EOS 400D DIGITAL
Date/time original 02.08.2007 19:04:43
Shutter speed value 1/400 s
Aperture value f/5.6
ISO speed ratings ISO 200
Focal length 100 mm



Crop from #1



Crop from #1

[puzzledpaul]

Another great DF shot Nikola

Re the dof issue, isn't it also relevant that the DF in this image is smaller in this frame than the F7.1 frame (assuming full frame again with first pic) - and thus different (lower) magnification?

With some rough screen measuring and assuming the DF was 75mm long, then I got (sensor) mags of approx. 0.19 (f5.6) and .25 (f7.1).

I probably used the wrong expression, but using these figs gave a greater dof for the 5.6 shot.

Trade-off is that there's fewer pixels in the lower mag shot.

(Rik'll no doubt put me right on the above ... )

pp

[rjlittlefield]

Nikola, you sure nailed this one, and that lens is beautifully sharp -- much better than my Sigma 105, I think.

PP, what you say sounds right to me, assuming that DF means "DragonFly". (At first I thought it meant "Depth of Field" in one place, and "DragonFly" in another, and I was getting a little confused. I guess the ol' morning coffee hadn't kicked in yet. )

Of course the DOF (Depth Of Field ) in the crops is much less than in the full-frame shot.

But if we take Nikola at his word that he nails the wide-aperture shots more often than stopped down, then it's an interesting question: "I wonder why that is?"

With my Sigma 105, I know from bench testing that the best focus point moves systematically backward over the first few f/stops. The point that's in best focus wide open tends to stay toward the front of the DOF range as the lens stops down. If I don't think about that, then I miss focus on more of my stopped-down shots.

I have no idea if Nikola's lens acts like that too. As a rule of thumb, better lenses should shift focus less (because the focus shift is due to uncorrected spherical aberration), and since Nikola's lens looks very good, I would expect it to show less shift than my Sigma. But I would trust a careful measurement more than thumbish theory any day.

--Rik

[beetleman]

The crops are soooooo beautiful Nikola. Just love all the detail to look at

[MacroLuv]

Thanks guys!
Paul, your assumption about DF size is very well but #1 from Dragonfly visiting my little isle is actually a crop fom size 3888 to size ~ 2900. So some changes are needed in your calculation. #1 in this post is a full frame size 3888 × 2592.

Rik, I mainly shot in Av mode (apreture priority) so I think that wide-aperture shots gives me more shutter speed (consider handheld and windy day). That could be a main reason why I have more success with wide-apreture shots.
I would also trust more in measurements than myself.