Infinite objectives , tube lenses and questions ...

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Macrero
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Infinite objectives , tube lenses and questions ...

Post by Macrero »

Hi all, I have infinite corrected objectives like Nikon CFI , I'm testing them with various tube lenses, and I can not get satisfactory results. My questions are: have to use tube lens of 200 mm or may be shorter or longer ? that distance should be between the objective and the tube lens ? and between the tube lens and the sensor ?? Any recommendation for tube lens? I would appreciate any information regarding this.

Thanks in advance!

Kind regards !

ChrisRaper
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Post by ChrisRaper »

I don't have infinity objectives but, from what I have read here, most people use lenses in the range 100mm to 200mm - focused on infinity. Any shorter and the image will not fill the sensor - much longer and it will go the other way. Can you maybe post some examples and then the experts here can look at what you think isn't satisfactory? :)

ChrisR
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Post by ChrisR »

NB, zoom lenses usually only work without vignetting, at the long end.
that distance should be between the objective and the tube lens ?
Close, is likely to give less vignetting, but it's not critical.
and between the tube lens and the sensor ??

Correct to focus the tube lens at infinity.
Any recommendation for tube lens?
It doesn't seem to be too important, a "better" lens only gives a marginal improvement.
What have you got to try with?

Macrero
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Post by Macrero »

Thanks ChrisR and Chris Raper , I'll keep trying ... This is a test stack with the Nikon CFI 10X/0,30 + Tokina 90/2,5 Macro as tube lens, I have no lenses above 100 mm , I have to buy any ... not bad at all, but far from the resolution of this objective ...

Image

Regards !

ChrisR
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Post by ChrisR »

My "0.3" falls off in quality more than the "0.25" towards the corners, particularly with a short tube lens, but it's fine towards the centre.

rjlittlefield
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Post by rjlittlefield »

Exactly which objective are you using? Can you post a picture of it, please, including all its markings?

I am a little puzzled because the only CFI 10X NA 0.30 objectives I can find in Nikon's price list are Plan Fluor's that surely should produce a sharp image at least in center. Using any of the 10X's at 4.5X, as you're doing here with a 90 mm tube lens, the center should be so sharp as to out-resolve your sensor.

--Rik

Macrero
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Post by Macrero »

Rik , the objective is marked Nikon CF Plan 10X/0,30 EPI ∞/0 , WD 16.5 . Is this:

Image

Tonight I will try to make a stack in my basement, where I have a concrete table to avoid the vibrations, which are my nightmare :evil:
I also will buy a 200mm lens to test with it ...

Regards !

ChrisR
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Post by ChrisR »

Errm, that's not a CFI, that's the earlier CF
There is an LU CFI 10x 0.30
(Suspecting, not sure - are the CFI and LU optics similar? )

I'm stealing Rik's thunder here. but also paying him the compliment of remembering his posts - look at this
, which is a test of your lens in its BD form. (Same optics, I believe).

This ties up with my own ad-hoc & random observations that 0.3s are OK on the middle, but don't hold up well away from that.
The central performance is close, maybe a little better, but in my case and perhaps others, may be limited by how they happen to work with a particular "tube" lens.
Last edited by ChrisR on Mon Apr 02, 2012 9:51 am, edited 1 time in total.

Pau
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Post by Pau »

Note this is a CF infinite(RMS thread, 45mm parfocal), not a CFI, a different standard (wider mount, 60mm parfocal).
It's a very sharp objective (but not a perfect one).

Some informal tests:
http://www.photomacrography.net/forum/v ... 9281#59281
Pau

ChrisR
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Post by ChrisR »

Lo sentimos Pau, me habia olvidado de tu post!

Macrero
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Post by Macrero »

Yes, it was a mistake, is an CF not CFI ... I know it's not perfect, but I also know that can give a much higher resolution than I get ... something wrong with my set-up , or with my technique ... I will continue with the method of trial and error , and hope to find the weak point 8)

Thank you all ! Regards !

rjlittlefield
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Post by rjlittlefield »

Thank you for posting the lens images. True, it's a CF not CFI, but still it should be very sharp in the center, especially when pushed down to 4.5X. At image center, there should be no compatibility problems with any tube lens, except possibly for flare due to reflections and that would not affect resolution for a high contrast subject like this one. I will be interested to see how it looks when shot on the concrete table.
look at this, which is a test of your lens in its BD form. (Same optics, I believe).
Different optics, I think. That thread tests the CFI 10X, but the CF BD is only a 5X. I don't own a 10X BD and don't recall ever testing one.

--Rik

ChrisR
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Post by ChrisR »

Ah, Freudian reading syndrome - or just wishful.. The Cf infinite 5x/10x both behave in much the same way.

Regarding the tube lens, I'm not sure if/where the combo would outresolve the sensor so lose the difference between the objectives, but I'm thinking that if the tube lens is the weaker partner then you'd not see it.
I can see that resolution as given by λ/2NA *M, is about one pixel here.

Macrero, could you show us some actual-pixel crops?

rjlittlefield
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Post by rjlittlefield »

I would also like to know for sure which camera.

I've seen elsewhere that Macrero is using a Sigma camera, and I believe the highest resolution Sigma DSLR available for use right now is still the SD15 with a maximum resolution of 2640 x 1760. Those pixels are larger than 8.3 microns, compared to a calculated value of 4.6 microns between peaks using 0.55/(2*0.30) *5, and we would need at least two pixels in that latter distance to see the separation between the peaks. By calculation then, we're quite far out-resolving a Sigma SD15 sensor, by a ratio of 8.3 to 2.3.

As a cross-check, I go back to my benchmark point that an f/11 optical image contains significantly more detail than is captured by a 15 megapixel APS sensor, where in Macrero's setup, the combo is running at f/8 and the pixels are bigger.

I agree that if the tube lens is bad enough, then the above calculation doesn't apply. Also if the tube lens is focused far from infinity, one might degrade the objective quite a bit.

--Rik

Macrero
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Post by Macrero »

Whoa, now I'm desperate, there is no way to get something decent ... Rik, the camera is a Sigma SD14, which has exactly the same sensor as the SD15, I had also thought that perhaps the "exotic" Foveon sensor is not the most appropriate for operating at high magnifications, the objective is good, the tube lens (Tokina "Bokina" 90/2, 5) is one of the best macro lenses ever made, then where is the problem ? the sensor ? I always thought that larger pixels (photosites) is better, does not it ? I have to try with another camera ...

This is done with the following settings: Nikon CF 10X / 0.30 > 36mm ext. tube > Tokina 90mm Macro focused at infinity > 10cm bellows extension, exposure time 1.3 sec. , ISO 100. With continuous light, but on a concrete table, and mirror lockup , cable release , etc ... 36 exposures , in steps of 20 microns , stacked in Zerene Pmax , with all settings turned off .

Image

crop

Image

Really desperate, right? :roll: :(

Kind regards and thank you all for your help !

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