Lasse Eriksson wrote: As you can see most of the throw in 2/100 is wasted to makro:
How can it be wasted when it's a Macro lens
Before 2/135 it was the longest tele lens on ZF/ZE-"series", so it has been used much more as generic tele than makro lens. If you look photos posted to here (e.g. Z* thread) or Flickr from 2008 to today you see that majority of photos shoot with the lens are normal tele shots, not makro photos.
Also personally I don't like so long throw on makro end, there is way more precision available on makro end than it's possible to use or needed.
Considering above I still think that majority of MP 2/100 focus throw is wasted to makro.
I too don't find the long throw on the makro end a waste...I prefer quick focus in normal distance and precision when doing close-up.
not really related to focus throw, but I recently found that the 100 MP does not work well with extension tubes.. so I don't know if it is possible to go beyond 1:1 with that the 100MP.
ytwong wrote:
not really related to focus throw, but I recently found that the 100 MP does not work well with extension tubes.. so I don't know if it is possible to go beyond 1:1 with that the 100MP.
Does it perform poorly with tubes? Perhaps a teleconverter or achromat close-up filter works better.
I have tested the 100 MP with PN-11 extension tube (52.5 mm) on my D300.
At 1:1 the combo is very soft at f/2 ('nominal' aperture), soft at f/2.8, very good at f/5.6 and fairly good at f/11 (where diffraction starts degrading IQ). At 1:1 the effective aperture is about 2-stop closer than the nominal one.
AhamB wrote:
Perhaps a teleconverter or achromat close-up filter works better.
I have tested the 100 MP with the Canon 500 D; good performance at intermediate apertures, but the max magnification is 0.75 X.
Ripolini wrote:
I have tested the 100 MP with PN-11 extension tube (52.5 mm) on my D300.
At 1:1 the combo is very soft at f/2 ('nominal' aperture), soft at f/2.8, very good at f/5.6 and fairly good at f/11 (where diffraction starts degrading IQ). At 1:1 the effective aperture is about 2-stop closer than the nominal one.
I'm not sure that's entirely unexpected though? 1:1 and f/2 will give you almost zero DOF anyway. By the way, you probably know this, but the aperture is only true f/2 at infinity focus.
Samuli Vahonen wrote:
Before 2/135 it was the longest tele lens on ZF/ZE-"series", so it has been used much more as generic tele than makro lens. If you look photos posted to here (e.g. Z* thread) or Flickr from 2008 to today you see that majority of photos shoot with the lens are normal tele shots, not makro photos.
Also personally I don't like so long throw on makro end, there is way more precision available on makro end than it's possible to use or needed.
Considering above I still think that majority of MP 2/100 focus throw is wasted to makro.
Zeiss might be able to provide a finer focusing thread for a better precision at infinity, but the proportion of throw 'wasted' on close focus would remain the same. That is just the way it is with a helicoid with a given pitch.
carstenw wrote:
Are you sure? I thought some lens designs had the helicoid feeding into a slot/cam system with a path defined as you wish?
Good point - it should be possible, I have had for example zoom lens, which was shortest at middle of zoom range. Should be possible to use non-linear slots for focusing as well. There must be some reason why it's not done, since all makro lens designers can't be idiots.
AhamB wrote:
I'm not sure that's entirely unexpected though? 1:1 and f/2 will give you almost zero DOF anyway.
You can calculate DoF by using the proper equation:
DoF = (1/Mē)xCoCx2xNx(1+M/P)
where CoC is circle of confusion (1/40 mm on FF), N the aperture, M the magnification and P the pupil factor (which is < 1 for telephoto lenses, see here).
AhamB wrote:
By the way, you probably know this, but the aperture is only true f/2 at infinity focus.
The effective aperture, N', depends on magnification and pupil factor, according to the following equation:
N' = N x (1 + M/P)
At infinity, M = 0 and therefore N' = N.
As I wrote previously, when M = 1:1 = 1, N' = 2N, i.e. two stops closer than the set aperture (by assuming P = 1). However, the pupil factor of the 100 MP at its minimum focus distance is 0.66 (according to a quick measurement I made) and, consequently, the max aperture of the 100 MP at 1:1 is, 2x(1+1/0.66) = 5.
Best,
Doesn't the calculation of N' assume Mag achieved through extension alone and not FL shortening or floating element adjustments? I can testify that the CV125 is about 1/2 faster at 1:1 then it should be if only helicoid extension were used.
carstenw wrote:
Are you sure? I thought some lens designs had the helicoid feeding into a slot/cam system with a path defined as you wish?
I am sure that the amount of throw dedicated to macro is necessarily large with a threaded focusing system that has a fixed pitch / lead. I am not sure that all lenses are designed this way. If not, I wonder how alternative focusing mechanisms work, whether they can provide the robustness and general absence of play that characterize Zeiss lenses, and what the extra cost would be.
Michael Gordon wrote:
Doesn't the calculation of N' assume Mag achieved through extension alone and not FL shortening or floating element adjustments? I can testify that the CV125 is about 1/2 faster at 1:1 then it should be if only helicoid extension were used.
You're right. For example, my AF-S Nikkor 105 VR effective aperture @ 1:1 is f/4.8.
However, the FL of 100 MP doesn't change significantly at the minimum focusing distance (its elements do not float as much as AF macro lenses ). If you look at the plot at page 16 of this report (www.zeiss.com/C12567A8003B8B6F/EmbedTitelIntern/CLN_35_Bokeh_EN/$File/CLN35_Bokeh_en.pdf) by Zeiss, you find that the 100 MP aperture changes by 1.7 EV at 1:2 (see also the Table @ page 18 of that report). This value is very close to the value we can calculate by using the above formula for N'. In fact, at 1:2 N' = 2x(1+R/P) = 2x(1+0.5/0.66) = 2x1.76.
1.76 is 'practically' equal to 1.7, so - in this specific case - we can neglect FL changes.
