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Tokina 100mm Macro as a tube lens on a nikon 10X
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All Ex



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PostPosted: Mon Jan 04, 2016 10:38 am    Post subject: Tokina 100mm Macro as a tube lens on a nikon 10X Reply with quote

Today I tried my Tokina 100mm Macro lens, which is a great lens, placing it behind my Nikon Plan 10X/0.25 as a tube lens. This set up gives me a 6X magnification.

This is the result of my set up :



Which means that I've placed my subject too close to my illumination surface (witch has two layers of diffusion material and enough dimensions in comparison to the subject)

D800, Tokina 100mm Macro, Nikon 10X/0.25, f3.2, SB800 in 1/128 power, 69 stacks.

That gave me a lot of vignetting.

What is your opinion on the illumination?


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Charles Krebs



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PostPosted: Mon Jan 04, 2016 12:15 pm    Post subject: Reply with quote

A quick shot of your set-up (and especially the lighting arrangement) would really help in regards to offering suggestions.

What stacking method was used? What "parameters" were used in the software.

The lighting really need some work. With a black or very dark shiny subject like this you need it much more diffused light, with the illuminated lighting surface nearly surrounding the subject.

As you seem to be aware, putting an objective designed for a 200mm tube lens on a 100mm lens will give you about 5X, but will not give you good coverage... illumination or image quality... on a full-frame sensor.
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rjlittlefield
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PostPosted: Mon Jan 04, 2016 1:03 pm    Post subject: Re: Tokina 100mm Macro as a tube lens on a nikon 10X Reply with quote

All Ex wrote:
What is your opinion on the illumination?

It looks like you have a lot of undiffused light coming from somewhere -- perhaps through cracks in the diffuser, or around the diffuser, and maybe bouncing off some other shiny reflector instead of coming directly from the light.

I have marked here some indicators:



The green arrow, at bottom, points to what the insect skin should look like when it is illuminated only with diffused light.

The red arrows point to "streaky hairballs" that result from undiffused hard light bouncing off curved surfaces, typically as rendered by PMax.

I had a similar problem happen by accident. See discussion at http://www.photomacrography.net/forum/viewtopic.php?t=16736 (just the part about "hairball").

--Rik
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All Ex



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PostPosted: Tue Jan 05, 2016 12:44 am    Post subject: Reply with quote

The real truth is that I had lots of reflecting curved things around my object (glass bottles and especially a tin one). I will definitely isolate my future subjects from the reflections around them by placing a tissue paper (should you thing it is a better idea to place black tissue around my photographic " studio") as a side material on my self made soft box, together with grown it taller to move the illumination surface further away and not so close to the subject.
By the way do you thing that blue haze :



has the same cause with the reflections above?

Finally I forgot to tell you that I used the Pmax method with it`s standard settings.
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Daniel_Han



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PostPosted: Wed Feb 03, 2016 4:26 am    Post subject: Reply with quote

Nice photo! Definitely need to watch the lightleaks though. I have the Tokina lens and it's a lovely piece of glass! I should get an objective and have some fun too Smile
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All Ex



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PostPosted: Wed Feb 03, 2016 5:11 am    Post subject: Reply with quote

I'm already prepared to deal with this problem.

It's a pity that this time of the year my friends do not find any insects to bring me. That's the reason I don't post any other photos.

We all have to learn a lot from this site, I'm learning since my first post here.
Thank you for your good words!

Very Happy
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ChrisR
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PostPosted: Thu Feb 04, 2016 7:13 am    Post subject: Reply with quote

Quote:
should you think it is a better idea to place black tissue around my photographic " studio"

I think you need something to diffuse light, very close to the subject. Perhaps about 5cm, and wrapped around the subject, would be convenient

Imagine you're the bug, looking out. The light source needs to look like a large "sky", maybe 150ยบ, not something bright which only sends light from a relatively narrow angle.
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All Ex



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PostPosted: Thu Feb 04, 2016 8:30 am    Post subject: Reply with quote

Above my subject lies a huge (compared with it) surface of diffusion material (32cm X32cm).
I`ve added an extra layer of baking paper, witch is a semi transparent paper, as an extra diffuser and I `ve taken two spheres of hallow white foam material witch can separate in half, I intent to use them as reflectors underneath my subject in a tilt that will provide space for the foreground to emerge , that way with two holes in the semi-spheres (one for the objective and one for my subject holder) and placing a frame with a card of my desired color(s) (witch I`ve already purchased and made the color cards) I intent to try my future efforts. My current problem is to find a steady place to mount my semi-spheres.

Wink
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ChrisR
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PostPosted: Thu Feb 04, 2016 6:31 pm    Post subject: Reply with quote

"Huge" isn't what's important, it's the angle that meters. How far away is the diffuser?
The angle is about 2 x (inv tan (16/d))

where "d" is the distance from the subject to the diffuser.
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All Ex



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PostPosted: Thu Feb 04, 2016 9:56 pm    Post subject: Reply with quote

I will arrange to put my subject in a 5 cm distance, as you told me before, (sorry but I am not familiar with inverting functions and the science calculator in my laptop doesn't help me, it gives me something like 145 when D=5).
Will that (5 cm) give me the proper angle?
What role will the hemispherical reflector play in the light composition of the photo? I guess it will help a lot.

Question
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All Ex



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PostPosted: Fri Feb 05, 2016 6:59 am    Post subject: Reply with quote

I have received the " reflectors " :



I think I have to place it higher, in the level of the insect.

Together with my other grabbers (witch vary in power of grabbing), I `ve modified my objective as you told me in order to avoid any ambient light :



That way and placing a colored card behind the object I intend to take my pictures.
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PostPosted: Fri Feb 05, 2016 1:13 pm    Post subject: Reply with quote

I have a concern about that lens shade.

With the length and width that it has, it will prevent light from hitting the front of the subject directly.

Your subject will end up being illuminated mostly from the back and side, with only a little fill light bouncing off the gray inside of the shade.

Your first priority has to be making sure that light hits the subject correctly.

Then -- only as a second priority -- you can worry about preventing stray light from hitting the lens.

As a matter of practice, I almost never try to shade my objectives because it causes more problems than it solves. I just make sure that the flashes or light bulbs do not shine directly on the front of the objective. As an example, the image at http://www.photomacrography.net/forum/viewtopic.php?t=16348 was shot with no lens shade, just the foam plastic cup diffuser as shown at http://www.photomacrography.net/forum/viewtopic.php?p=104602#104602.

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All Ex



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PostPosted: Fri Feb 05, 2016 4:09 pm    Post subject: Reply with quote

In another post, that I can't find now, ChrisR (if I recall correct) proposed that construction on the objective, to prevent direct light of hitting the front of the lens.
I could always target my object from above it (as the narrow dimensions let me to do so). I intent to use mostly my 200mm MF lens, witch has definitely smaller dimensions, and one way or another I`ll try to avoid shadow from my lens to my object.
Anyway thank you for sharing your thoughts with me.

Smile
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PostPosted: Fri Feb 05, 2016 4:53 pm    Post subject: Reply with quote

If you are going to use a lens shade, use a cone-shaped one (sawn-off cake decorator tips work well and come in many shapes), and don't use something white. I line my cones with black Protostar.
'
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PostPosted: Fri Feb 05, 2016 5:05 pm    Post subject: Reply with quote

Rik what you're seeing as grey is I think white foam being used as a diffuser.


I believe Alex you were thinking of this:
http://photomacrography.net/forum/viewtopic.php?p=181366#181366

Yes - that was intended as a diffuser, not a lens shade - though it would behave as both.
Sometimes I have found light getting into an objective "from the side" and reducing contrast, therefore shades ...
As ( a couple of old pictures)


the first pic shows using just a small piece of black PVC tape.
Also some aluminium sticky tape on the Mitutoyo - there's black paper inside it. (The shade slides off)




By the way. I think you're using a plastic foam as a diffuser.
If you take a photograph of it with a flash behind, you may be surprised how much light goes straight through. Ordinary paper is better. A second sheet, with a separation between them, adds significantly to diffusion.
Tissue paper (ie Kleenex) works well too but of course doesn't stand up so well.

I hope you've attended to shiny surfaces on the INSIDE of the tubes & rear end of the lens. That's more important than an external shade, in the case of a normal objective.
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Last edited by ChrisR on Sat Feb 06, 2016 2:32 am; edited 1 time in total
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