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PostPosted: Fri Nov 07, 2008 5:44 pm 
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The few reviews I've seen so far hinted at increased magnification with either sigma TC, but so far I've not managed to find actual samples. I'm not too concerned about the increased magnification actually, it's more the reach I'm after.

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Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.


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PostPosted: Fri Nov 07, 2008 6:19 pm 
From sigmaphoto.com:
Lens: Converter:
Focal length
Aperture
Focus
Max. Mag.

150mm F2.8 EX DG Macro 1.4X 210mm f/4 AF *1 1:4.1
150mm F2.8 EX DG Macro 2X 300mm f/5.6 MF 2:1
180mm f/3.5 Macro 1.4X 252mm f/4.9 AF* 1.4:1
180mm f/3.5 Macro 2X 360mm f/7 MF 2:1

Link


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PostPosted: Fri Nov 07, 2008 6:48 pm 
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I suspect it's a typo of mixed up colon and decimal point. It doesn't make sense otherwise. But looking further, it is a little disappointing that AF doesn't work with the 2xTC as f/5.6 should be bright enough. Must be some other limitation.

_________________
Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.


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PostPosted: Fri Nov 07, 2008 6:52 pm 
Yes typo :) I tried to correct it with spaces, but all spaces got deletd :/
However there's a link down, where you can see it on the side.

Btw, can you explain short about the focus and aperture? Never truly understood it :)
Right now it makes no sence to me. My kit lens is f5.6 when racked out, and it focuses. A lot of lenses is higher than 5.6, and they still autofocus.


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PostPosted: Fri Nov 07, 2008 7:25 pm 
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On the typo, I meant I suspect the data on Sigma's site appears to be incorrect.

The short version on AF is the sensors need enough light to work. The maximum aperture that AF is rated for is typically f/5.6 except on high end bodies. So as far as Sigma 150mm+2xTC is concerned, there should be enough light. I can only guess at what other reasons there are so it is described as MF only.

Then again, with MF being typically chosen for macro I guess it's not a big deal after all...

_________________
Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.


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PostPosted: Tue May 26, 2009 9:28 am 
Hi,

I've got a question related to aperture shrink when using macro lenses with decreasing subject-to-focal-plane distance.

I'm OK with the fact that macro lenses behave like that the closer you get to 1:1 scale. As I discovered some lenses report this actual aperture to the camera and some do not. Now, does the same rule apply to other lenses as well ? I'm debating between Sigma 150 2.8 macro and Nikkor 135 2.0 DC (I realize they are different beasts) and was just wondering if the same law of physics impacts telephoto lens as well.

thanks
Greg


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PostPosted: Tue May 26, 2009 11:49 am 
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As long as we're existing in this universe, the same laws of physics applies to everything.

The effective aperture is the actual aperture multiplied by 1+magnification. I first saw this in the Canon MP-E65 manual where it is more important from higher magnifications possible. For a typical 1:1 macro lens, used at 1x magnification and actual aperture at f/2.8, the actual aperture is multiplied by 2 (1+1) and therefore effective aperture is f/5.6. This explains the earlier question I had on why macro lenses seem to have AF limits with TC connected, and also why macro prime lenses mostly seem to be f/2.8.

I don't fully understand the impact of it. I don't believe it affects the DoF or diffraction effects, but it does affect the amount of light reaching the sensor. Therefore as magnification increases, the exposure needs to be longer to compensate for this "light loss".

For all the camera+lenses I have, the camera always shows the actual aperture not effective aperture. I'm not familiar with Nikon though, so I don't know if they might be different from Sony or Canon.

If we go back to the original equation and apply this to a "normal" scenario, the lens will be used at very low optical magnifications. The effective aperture is therefore going to be close to actual aperture. Therefore no significant correction is needed.

_________________
Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.


Last edited by popo on Tue May 26, 2009 4:41 pm, edited 1 time in total.

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PostPosted: Tue May 26, 2009 1:10 pm 
Thanks for the explanation popo. You mentioned that the effective aperture affects the light reaching the sensor but does it affect the DoF as well? Or is that still a function or the actual aperture?


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PostPosted: Tue May 26, 2009 1:27 pm 
Thanks popo,

Really appreciate your explanation.
So, for telephoto lens when working with lower magnification this adjustment to shutter speed in order to compensate for the light loss should be negligible and in practice may be disregarded (for analysis, of course; the metering does everything for you), right ?

Speaking about the Sigma 150. I only was able to test one which was not reporting the change in aperture to my camera (2.8 regardless of magnification). Anyone knows at what distance this shrink kicks in ? I know it begins whenever you focus closer than at infinity, but the question is when the lens starts to report it ? (if it does it)

thanks
Greg


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PostPosted: Tue May 26, 2009 4:36 pm 
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The Sigma 150/2.8 on my D300 body clearly shows the effective aperture. Starting at 3m it reports f/3.0, from 1.3m it is f/3.2 and so on. Don't know whether other non-macro lenses report that effect too.
And yes as the lens get's darker the exposure corrects for that.
As to dof: It all depends what your dof-calculator factores in. Normally when focussing closer dof get's much, much thinner and that is not compensated for by any change in effective aperture.

@popo: your formula is right but only for a simple lens. If you factor the effects of internal focussing in the outcome might be more favourable. See my comparison of this effect with the micro-Nikkor 105/2.8 VR (see this post).

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Thomas (beware: Nikon-fanboy and moderator!) My Lens Reviews, My Pictures, My Photography Blog
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PostPosted: Tue May 26, 2009 8:55 pm 
Thanks Thomas,

I've recently tried 2 Sigmas and both were non-reporting on my D700 in terms of aperture shrink. I do not know the serial numbers, though (which might hint on whether the software was modified or not).

You're saying your Sigma starts at f3.0 from 3m. Does it ever go to f2.8 ?

Greg


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PostPosted: Tue May 26, 2009 9:52 pm 
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Greg, above 3m it shows f/2.8.
And as to the age of this lens: Well, I reviewed it the day I got it. So have a look at the first post in this thread.

P.S.: I edited the quote out from your post. There's no need to quote the directly preceding post unless your referencing to a specific sentence or part of it. This way the thread is much leaner and easier to read.

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Thomas (beware: Nikon-fanboy and moderator!) My Lens Reviews, My Pictures, My Photography Blog
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PostPosted: Sat Oct 03, 2009 6:17 pm 
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I noticed that I didn't test for longitudinal CAs so went out today to repeat the test shots that led to the shocking example that you can see in the linked thread above. Btw. that example was shot with the AF Nikkor 180/2.8D.

Well, what can I say: I saw no hint of greenish or reddish tint in oof areas! No need to post a picture.
Here again the Sigma 150/2.8 APO macro is a little better than the Nikkor AF-S 105/2.8 VR.

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D800+assorted lenses


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PostPosted: Thu Dec 17, 2009 9:13 pm 
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Just one additional note on focusing:
I had no probs with AF in my test-shots. But currently I'm testing the new Nikon 70-200/2.8 VR II with the aid of Camera Control Pro2 to make sure that I've properly focused the lens. You get a better view in live-view to judge whether focus is critically sharp than on the in-camera lcd-screen.
What I found out is that with the Sigma 150/2.8 the focus control in Camera Control Pro 2 was too coarse to properly adjust the focus of the lens, while with the Nikon 70-200 everything works fine and dandy.
This confirms what I have already seen with live-view aided MF on both lenses: The Nikon 70-200 has a much more forgiving gearing when fine-focusing than the Sigma 150.
But then the Sigma is a macro lens with a much wider focusing scale (1:1 till infinity) than the Nikon (1:8.3 to infinity).

Just wanted to let you know in case you're planning to use Camera Control Pro 2 with the Sigma 150/2.8.

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Thomas (beware: Nikon-fanboy and moderator!) My Lens Reviews, My Pictures, My Photography Blog
D800+assorted lenses


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PostPosted: Sun Dec 27, 2009 2:05 pm 
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Here is a new series of test-shots comparable to the review of the new Nikon 70-200/2.8 VRII zoom I'm currently writing. The second row shows a close competitor to this lens from Nikon

Sigma AF 150mm 2.8 EX DG APO HSM IF macro:
Image

micro-Nikkor AF-S VR 105mm 2.8G IF-ED:
Image

Developed in CaptureNX with standard settings plus exposure compensation to bring all images to a comparable level of brightness. These shots were taken with hand-optimized focus in Camera Control pro 2. This 100% crop was taken 12mm off center which is equivalent to the wider DX border or approx. 60% of the FX-diagonal.
The fascinating observation is that the Sigma shows almost no degradation when used fully open. Again, the Nikon is a little weaker at f/2.8.

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Thomas (beware: Nikon-fanboy and moderator!) My Lens Reviews, My Pictures, My Photography Blog
D800+assorted lenses


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