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Extension tubes Help please

A

ajs

New Member
Hey guys

ive been doing alot of shooting with my 500cm, and 80mm cf t* recently, and getting great results in studio portraits ive been shooting in black and white. It really nice to have a much bigger neg to work with that i was previously used to with 35mm. Anyway, i need some help with extension tubes.

I only have the 80mm at the moment, and while id love to go out and get both the 50mm, and the 150mm, i cant really afford it at the moment. In my portraits, id just like to get a little closer framing, and reserch has told me that i need a small extension tube. Looking about there is an 8mm, and a 10mm. Both seem to provide about the same ratios, but there seems to be a bit of talk about which ones go with which bodies and lenses. Will the 10mm tube work for me, or would the 8 be better- all i want is a slightly tighter framed portrait. Is there any comatablilty issues with either of these tubes with the stuff ive got, or anything else for that matter?

Also, does anyone here use either of these with the 80mm for portraits, and how do you find them? How much does the tube affect quality (im thinking not alot, because theres no glass in them- but am not sure?). Any reccomendation? Sorry for all the questions, and thanks to anyone who replys.

Cheers
-Adam
 
Adam: I have an 8mm tube that is like new. Bought it new. Rarely use it. Write to me at slroti@earthlink.net if you are interested in it.

When you are able, get the 150 mm lens and couple it with a 21 mm tube for facial portraits with out of focus backgrounds. Very effective combination.

Scott Roti
 
Hey

scott cheers, but im looking for one really cheep (i am a very, very skint student at the moment), and i think you'll probably want to get more for it than ive got to spend on it (i keep watching them on ebay)- they seem to go for about 40 quid every so often... just havent been lucky yet. if you willing to sell it for about that much drop me an email- adamspeck@gmail.com

Stig, cheers, ive already downloaded that, thanks for the link anyway.

it dosent mention the 10, and only breifly skims over the compatability- thats why i want to check... i read over it again, and its deffinetly the 8 i want first anyway, but the 10 seems to reguaraly go cheeper, so i wanted to know whatever i can about the 10, and whether it overlaps with the lens focusing, so you dont have to take it on and off, or whether the extra 2mm will make there a step... (by this i mean- the range of focusing with the tube and the lens overlap- i know that infinity focus is imposible with it on.) ok im finding this hard to put into words, and starting to ramble...

basically- with my set up of a 500cm, and an 80mm cf t*, will i miss anything by going for the 10mm instead of the 8mm? any reason to chose the 8mm over the 10mm? i just dont want to buy one, then realise i bought the wrong one...

thanks again, all replys appreciated.
-Adam
 
With a 500 C/M and an 80mm there won't be a problem with either (obviously fractionally less extension with the 8mm). The 10mm is the earlier version short tube.

The 'new' series of 8/16/32/56 gives a seamless range of extensions combined with the extension on 80mm lenses. This is presumably the reason for the
change in extension.

The only camera limitations with the very short tubes are with focal plane shutter 'blads, so it doesn't worry you.

BTW, you will need the short tube for close portraits (eg head shots) with a 150. The 50 being a retrofocus wide angle is not recommended for use with a tube (although one can). The combination will probably be too close a working distance for close portraits anyway and give an exaggerated and ugly perspective! Stick to the 80!
 
slroti said:
Adam: I have an 8mm tube that is like new. Bought it new. Rarely use it. Write to me at slroti@earthlink.net if you are interested in it.

When you are able, get the 150 mm lens and couple it with a 21 mm tube for facial portraits with out of focus backgrounds. Very effective combination.

Scott Roti
Click to expand...


Please what the 21mm value mean?
I have a 150 mm lens and I would like to use the ext. tube. What mean if I have e.g. 55 mm ext. tube.
What is the difference btw. 21 mm and 55 mm ext. tubes?

Thank you Jan
 
flashmxfreak said:
Please what the 21mm value mean?
I have a 150 mm lens and I would like to use the ext. tube. What mean if I have e.g. 55 mm ext. tube.
What is the difference btw. 21 mm and 55 mm ext. tubes?

Thank you Jan
Click to expand...

So what would you think the difference is?

How about 55-21=34mm

Wilko
 
Jan,

The distance between the lens and an object in front of the lens that is in focus is linked to the distance between the lens and the film.
To bring objects close to the lens in focus, the distance between lens and film needs to be made larger.

One way of doing that is by using the focussing helicoid that is built-in to the lens: when focussing closer, the lens is moved forward, away from the film.

There is however a limit to how much extra distance you can build into the focussing mechanism of a lens, and to be able to focus even closer than the lens allows, you can add tubes between the lens and the film.
The lengths of these tubes determine how close you can focus: the longer the tube, the closer you can get to an object and have it in focus.

The numbers attached to the different Hasselblad tubes indicate the length of the tube: the higher the number, the longer the tube, the closer you can get using it.
The 21 mm tube adds 21 mm between lens and film, the 55 mm tube adds 55 mm between lens and film, so you can get closer using the 55 mm tube.

How close you can get using any of the tubes depends on the focal length of the lens too.
And on whether or not - and if so, how much - the focussing mount is also used to increase the distance between lens and film.

There are formulae that help calculate these things. For these, and an explanation, see here:
http://www.hasselbladhistorical.eu/HT/HTComp.aspx

If you do not like doing maths yourself, there is a calculator that does the work for you here:
http://www.hasselbladhistorical.eu/HT/HTCuC.aspx

Note that when increasing the distance between lens and film, i.e. focussing closer, not only the obvious things, like lens to object distance and field of view, change, but also the brightness of the image projected by the lens.
So you need to correct the exposure when focussing closer, both with and without using extension tubes.
Above links give an explanation and show the effect on exposure too.
 
gnu,
thank you very much now I understand finally how the ext. tube works.
Please can you explain me these questions yet?
  1. Hasselblad 55 Extension Tube, can be used with 150 mm CF T* ? If yes, would you recommend if for portrait photography?
  2. I don't know how to work with the application here: http://www.hasselbladhistorical.eu/HT/HTCuC.aspx
    If I make an input in on of the fields of the app I get application error. And I do not know what values should I put in this fields :(
    How can I in practice calculate the f-stop and shutter speed. Must I keep in mind the formulas of the page http://www.hasselbladhistorical.eu/HT/HTComp.aspx#CalcProc. Or exist some clever technique how to make it? Or calculate it and print it on the paper and have it at hand?
Thank you Jan
 
Jan,

Yes, you can use the 55 mm tube with that Hasselblad lens.
The maximum field of view (i.e. with the lens' focussing mount left to infinity) will then be 15,4 cm, the minimum field of view (with the lens' focussing set to the near limit, i.e. the lens fully extended as well) will be 11.2 cm.
Too small for portrait. A 16 mm tube wil be much better.

To use the calculator, you have to firts select the lens from one of the frop down menus above.
Then you choose which one of the input fields you want to use as input.
Say we want to know the maximum field of view you get when using a 16 mm tube on a CF 150 mm lens.
- First select the 150 mm lens from the "CF Lenses" menu. When you do, the page will reload with the data for this lens filled in the information and input fields.
- We want to know the maximum field of view when using the 16 mm tube, i.e. use only the 16 mm the tube provides, so we enter 16 into the "Total extension" box, and then click "Calculate".
- The result of this combination of lens and extension will be displayed in al other boxes, including the "Field of view" box, which reads 402.44 mm. 40 cm.

When using the extension that is provided by the focussing mount (about 21.2 mm) as well as the 16 mm the tube offers, we enter 16 in the "Extra extension" box and click "Calculate".
If now an error page is displayed (which i notice may indeed happen!), select "How to" on the left, and then go back to the calculator by clicking "Q.G.'s V-System Calculator" on the page that then appeares. You then have to again select the lens fisrt.
If all goes well, the result will again show in the "Field of view" box, which now reads 229.46 mm, 23 cm.

So using the 16 mm tube, the field of view ranges from approx. 40 to 23 cm. A perfect range for 'head shots'.

The "Aperture", "Shutterspeed" and "Exposure value" boxes/field are mainly informative. They show how a metered setting of any one of these must be changed to maintain correct exposure. For instance, if your meter suggests to use f/8 when using a certain shutterspeed, the Calculator shows that when using the lens' full extension plus the 16 mm tube as extra extension, you need to set f/6 instead of f/8 to keep exposure correct at that (unchanged) shutterspeed.
Same with the "Shutterspeed" field. Both it and the "Aperture" box allow selecting another setting, to find out how it has to change to keep exposure correct. The "Exposure value" field only shows the uncorrected and corrected exposure values the values in the "Aperture" and "Shutterspeed" boxes constitute.

But i see doing this will generate errorpages too.
I will look into why these application errors occur. I'm sure the Calculator worked fine before the site moved to a different server, and haven't really tested the thing after the move.

I find that a short printed table of date relevant to the lenses and tubes you have works fine when i do not have acces to the calculator. Though i know the formulae by heart, and can make do with a simple pocket calculator, the asymmetry of most lenses makes an extra correction necessary, which can only be calculated with the data for that particular lens, so if i must carry these, a already calculaed table will do even better.
 
Hi Wilko, just recognised a contributer, have been off this forum for sometime it is good to see people still here. Is Marc still about?

With regards to extension tubes I use a 150mm with an 8mm extention for portraits, it depends how close one needs to get and the style of portraiture.

Some shots that I wanted to do, cut out the hair line and some of the lower neck to get in tight and expose the eyes as the main focal point. With this CFV I will need to experiment with combinations. I am looking for a 16 mm extension so that in combination with the 8mm I will have a 24mm extension,
which will prevent purchasing a 21mm, already have a 32 and 56.

all the best, Carl
 
carl_sanders said:
Hi Wilko, just recognised a contributer, have been off this forum for sometime it is good to see people still here. Is Marc still about?

...

I am looking for a 16 mm extension so that in combination with the 8mm I will have a 24mm extension,
which will prevent purchasing a 21mm, already have a 32 and 56.

all the best, Carl
Click to expand...

Yes, Marc is still around, no worries.

I have sold my 55, keeping the 21 for use with the C150 or the recently acquired CF250.

Wilko
 
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