Focusing when using extension tubes

[jonathan_montague]

<p>Hi all<br />My first outing with my 56mm extension tube has left me with a rather simple question. 
How on earth can you focus accurately ?<br>

<br />My set up is as follows. 501cm/80mmPlanar OR 120mm Makro/56mm Ext. I realise 56mm is rather extreme, maybe 32 or 16 would be better in the field...<br>

<br />I was out trying to capture a rather nice toadstool in the woods. Using the 80mm I have the aperture wide open to see anything in the view finder. I realise this may be a very silly question but is it right that you have to have the focus ring set to infinity to get your subject in focus at all? I found the only way was to set it at infinity and move the camera until the subject was in focus. this was a working distance of approx 30cm. this left the very front part of the toadstool in focus and everything else wildly out of focus. using the focus ring seemed to have very little effect? I also tried with my 120 Makro - same thing but increased working distance, the focus ring did have the effect of slightly magnifying the subject but overall not much changed.. most noticible difference using these 2 lenses was that when using the 120 the brightness in the viewfinder is not affected when reducing the aperture.<br>

<br />I found it REALLY hard to tell if i had 'spot on' focussing when using this Ext tube. and Im left 'guessing' at what the given DOF will be when I stop doen to take the shot (i realise there must be charts for this)<br>

I have the Wilde manual but cant find anything specific about focusing when using Ext tubes.the rest of my process is..<br />Once happy with the composition I took my reading, added correction for the extension, dial down the aperture, close the viewfinder, lock the mirror up, and release the shutter using a cable release.<br>

<br />I dont have the results back yet so maybe this is a bit acedemic (hopefully they are all focused just as I intended!!?)<br>

<br />sorry if these questions are a bit at the 'beginner end'.. got to start somewhere!<br />jonny</p>

[q.g._de_bakker]

<p>Welcome to the world of close-up photography! ;-)</p>

<p>Yes, focusing is hard. DoF is almost non-existant, and it's difficult to decide what to put focus on. That, however, is the most important thing: you will have to decide what will be in focus! All the rest, everything else, will not.</p>

<p>Focusing is done by moving the entire camera to or away from the subject.</p>

<p>You do not need to have the lens set to infinity to be able to focus.<br />The focusing ring just changes the amount of extension, and thus the magnification. With a long tube, like the 56 mm, the approx. 9 mm the focusing mount of the 80 mm lens can contribute does not make a big difference. The approx. 27 mm the 120 mm brings along would suggest a bigger effect, yet it still is small.</p>

<p>You really should see an effect when stopping down either lens.</p>

<p>The <a href="http://www.hasselbladhistorical.eu/HT/HTCuC.aspx">online Close-Up Calculator</a>, specific to Zeiss/Hasselblad lenses, will give you an idea of what adding how much extension to what lens does.</p>

[craigd]

<p>In my experience, with all but the smallest extension tubes, it hardly matters what focus distance the lens is set to. You can use it to fine-tune focus once you have the camera in almost exactly the right position.</p>

<p>DoF is shallow, but the larger viewfinders of medium format make it, if anything, a bit easier to focus accurately than with 35mm. As long as your lens does not shift focus when stopping down, just focus wide open, stop down, meter, and shoot. Locking the mirror and using a remote release are optional but advisable.</p>

[jonathan_montague]

<p>thanks guys. it seems i may get some rather useless results (way way overexposed) from the shots i made with the 120mm as i have just discovered the button/slide switch on the LH side of the lens which seems to open the leaf shutter totally?! so ive shot all those at the widest aperture. oh dear! first time using that lens in anger I should expect some user error. do feel silly now though :(<br>

luckily i can get to the same subject easily and re-shoot those tommorrow.<br>

as for the focussing issue - that makes sense as i was seeing more effect from using the focus ring on the 120mm than the 80mm but i found the best focus was at infinity? Focus point and DOF still, to me, seem like its a bit of a hit and miss affair ?.. for example; looking in the viewfinder@f2.8 with the 80mm+56mmtube gives a DOF of maybe 3mm ? so once i have focussed on a chosen point... If I then take my aperture down to say f22, of course I wont tell any difference in dof in the viewfinder but the result should have a greater DOF than what i am actually seeing at f2.8 ? so in effect you are better off using a chart/formulae to give you the DOF parameters when using extensions ? is that right ?<br>

phew. i can tell this is gonna be an expensive learning curve!</p>

 

[WJT]

<p>Hi Jonathan. I use several lengths of extension tubes in various combinations with a Pentax 6x7 and I am sympathetic to your experience. To make things easier, you need a sliding camera mount so you can move the camera position in small increments. One such example, there are others, is from Manfrotto and is their<a href="http://www.bhphotovideo.com/c/product/554343-REG/Manfrotto_454_454_Micrometric_Positioning_Sliding.html"> 454 Micrometric plate</a>. I use this and it works fairly well considering its price point. For lower magnification work it is fine; if you do a lot of higher macro you may need better. But you get the idea. Regards.</p>

[jonathan_montague]

<p>walter thats a great piece of kit! now on my list as well as the 16 and 32mm tubes :)</p>

[q.g._de_bakker]

<p>Jonathan,</p>

<p>Hasselblad lenses have an automatic diaphragm. The tubes link the diapragm mechanism to the camera.<br>

The slider on the lens is a DoF preview lever. The diaphragm is normally open to allow focusing, and the slider closes it to the set aperture size. But only for viewing purposes. The moment you press the release button, the lens should close to the preset aperture no matter what you do or did with the slider.<br>

So your 120 mm lens should take pictures at whatever aperture you have it set to, without you having to do something extra.<br>

If it didn't, it needs a repair.</p>

<p>Focusing is not a hit and miss affair, but needs your attention more than it does in long range photography.<br>

As mentioned before the setting of the focusing ring does not matter much. It adss extension, changing both magnification and focus a bit.<br>

For good results and keeping magnification a constant, you should focus by moving the camera as a whole.</p>

<p>For that, i can only add my recommedation for the Manfrotto slide.<br>

Get two and mount them cross-wise. That way you can fine tune the position of the camera perfectly.</p>

[jonathan_montague]

<p>ahh phew! QC thank you for that info, Ive just tested that explanation with a long exposure so i can see whats going on with the 120mm shutter and it is of course as you have explained. I have done a bit of macro work with digital using extension tubes so am familiar with moving the camera (or subject) to focus, i think its the darkness of the WL viewfinder that is throwing me, also not being able to use just one eye to really get it pin point sharp. maybe an eyepiece would help.</p>

[Ed_Ingold]

<p>The WLF has a 4.5x magnifier - more than any other finder and great for fine focusing. You hold your eye right up to the magnifier and can still see the whole screen. A prism is going to be a bit brighter, and in my opinion, easier to use. But the magnification is less, between 2 and 3. There are auxillary magnifiers which attach to the 45 deg prism which magnify the center part 6x, but you can't see the whole screen.</p>

<p>Check to see if you have an Acute-Matte or Acute-Matte D screen. They're brigher than older screens, and may have been exchanged to be sold separately. Plain screens are the best for closeups, if you can find one. The split-prism devices don't work very well once you add extension tubes.</p>

<p>You can find a good take-along guide here - <a href="http://www.hasselbladusa.com/media/b257f2b0-cd24-497b-b21f-47dcf6ee295a-Closeup.pdf">http://www.hasselbladusa.com/media/b257f2b0-cd24-497b-b21f-47dcf6ee295a-Closeup.pdf</a>. There's more information yet in "The Hasselblad Manual" by Ernst Wildi (Ed. 5 or 6).</p>

[ingemar_lampa1]

<p>+1 on what Q.G. says.</p>

<p>A personal preference: if possible, use a flash (fill-in) even outdoors. It helps to get the focus right . At least for me.</p>

[jonathan_montague]

<p>well, must admit having discovered the pop up magnifier in the viewfinder, focusing is less of an issue!! shot another roll today in the woods, it had just rained followed by bright sunshine, found some lovely damp area's with various fungus and moss sporophytes, tiny micro forests within the forest. hopefully with some of the bracketing i did at least a few will be correctly exposed. Im still not that confident of how I am compensating for exposure loss due to the extension. it was 1.5 stops so i was either widening the aperture 1.5 stops or increasing exposure time by 2 stops. fingers crossed some have worked. I shall post the best results for contributors to see.<br>

thanks</p>

[john_golden2]

<p>i use the rb67 with 45mm and 82mm extension tubes, usually one at a time that way i can handhold and like the above stated just move the camera back or forward till you get what you want, here is an image with the 45mm tube and 127mm c lens. good luck</p><div></div>

[jonathan_montague]

<p>http://www.flickr.com/photos/39754091@N03/sets/72157625126301164/<br>

really quite pleased with my first MF close ups. I was using expired velvia 100f, I think the quality of scan could have been better (done at the lab).some of the shots seem to have a slight cast. out of 22 shots taken only 2 were heavily underexposed.</p>