extention tubes vs. macro lens for a specific purpose

[vladimir_m]

<p>Hello everyone,<br>

I have my canon 6d camera + 100mm f/2.8L macro lens which I use for "scanning" film negatives. I don't use it for any other purpose (i.e. no macro shooting, no bugs, nothing). </p>

<p>I usually scan my medium format film, but sometimes I also do scan 135mm film. So 1:1 magnification is important.</p>

<p>I was wondering if I can get the similar results with a very good prime lens + extention tubes? I'm talking only about quality here. I don't care if it will be bulky or take time to put on, etc. I will not be shooting macro in the field.</p>

<p>If the same quality is achieveable I will consider selling the 100mm macro and getting something like Sigma 50mm 1.4 art with a set of tubes instead. Just don't like the fact that expensive macro lense is collecting dust most of the time :)</p>

<p>Any opinion will be much appreciated, thanks :)</p>

[Alan Marcus]

<p>Prime lenses are fixed as to focal length. These lenses are optimized to image distant objects. A true macro lens is optimized to image at unity (1:1 magnification 1 life-size). At unity there is very little depth-of-field; thus most subjects are flat. Prime lenses are designed to image a curved world and project an image on the flat surface of film or a digital imaging chip. That translates to the fact that the rear of the lens is optimized to image a flat plane. For this reason, primes when tasked to image at unity often perform best when inverted. Thus the prime is often mounted on extension tubes with a reversing ring. Now the rear of the lens faces the subject. This configuration yields a higher resolution. To obtain unity, the prime is extended forward one focal length. Extension tubes and the reversing ring de-couple the lens electronically from the camera body. Now you are on your own to manually adjust the taking aperture. The distance subject to focal plane at unity is 4 focal lengths. In this configuration the f/#’s engraved on the barrel are invalid. This error is called “bellows factor”. The error requires the lens aperture be opened two f/stops. <br>

<br>

A true macro is optimized to image at unity. It is optimized to image a flat subject. The macro design counters “bellows factor” thus the f/#’s remain accurate. Magnificent images are obtained both with a macro and a prime with extension tubes. The macro design, by its very nature, takes the pain and drudgery away. </p>

[vladimir_m]

<p>Thank you so much Alan for the extended explanation. </p>

<p>To summarize what you have posted:<br>

1. The image quality of a dedicated macro lens can be achieved with normal lens using extention tubes and reverse ring.<br>

2. If extention tubes are used without a reverse ring there will be higher distortion compared to a macro lens or a lens w/reverse ring.<br>

Please correct me if I'm getting it wrong.</p>

<p>Regarding the bellows factor. For example, I use the reverse ring + ext. tubes and a modern 50 mm 1.4 AF lens with no mechanical apperture ring. With the lens electronically detached from the camera I am left with the apperture set to 1.4, which means 2.8 with bellows factor applied. Is that correct? </p>

<p>Thanks again!</p>

 

[gideon_kok]

A modern 50mm would need to be

stopped down to a smaller aperture to

give useful sharpness. The optical

formula is not designed for close-up.

You would need a set-up with a

mechanical aperture control of sorts.

Even then I am convinced the iq will not

be as good as can be achieved with a

good macro.

 

If you will not need a macro lens rather

consider a film scanner instead

[bebu_lamar]

<p>Even with the best of macro lenses I wouldn't use the lens at wide open for such a purpose. The lenses naturally perform better stopping down a couple of stops or so and you would need some DOF to compensate for film curling etc.. You can use a relatively long exposure for such an application so large aperture is not necessary. </p>

[William Michael]

<blockquote>

<p>I was wondering if I can get the similar results with a very good prime lens + extention tubes? I'm talking only about quality here.</p>

</blockquote>

<p>Similar yes, <strong><em>better</em></strong> I don’t think so.<br>

For most purposes I think that the 100mm macro lens that you have would produce <strong><em>better</em></strong> IQ than any Prime Lens which is not a macro lens and using Extension tubes.<br>

Perhaps the exception is the EF 50mm F/2.5, but that is not really “<em>not a macro lens</em>” for the situation that you are describing.</p>

<p>WW </p>

[William Michael]

<blockquote>

<p>"You would <em><strong>need</strong> </em>a set-up with a mechanical aperture control of sorts."</p>

</blockquote>

<p>That is not correct. <br /> One <em>might</em> need manual aperture control in some circumstances: but using and EF Lens and extension tubes that have electrical connections, one does not.<br /> If the OP chooses to use Extension Tubes and an (auto Aperture) Prime Lens, the the job would be made MUCH easier if tubes with electrical connection are employed.<br>

I've also seen a DIY rig that extends the electrical connections via a ribbon cable for a reverse mounted lens. </p>

<p>WW</p>

[vladimir_m]

<p>@<a href="/photodb/user?user_id=7393441">Gideon Kok</a>,</p>

<blockquote>

<p>If you will not need a macro lens rather consider a film scanner instead</p>

</blockquote>

<p>Film scanner has even narrower variety of applications than a lens. I can't justify spending ~$1000 on Epson V750 to achieve results comparable with my current setup. </p>

<p>@<a href="/photodb/user?user_id=5994753">BeBu Lamar</a>,<br>

Yes, that's what I do - I scan at f/9-11. Depending on a film type the exposures are 1/5 to 3.5 seconds.</p>

[vladimir_m]

<p>@<a href="/photodb/user?user_id=2223148">William W</a></p>

<blockquote>

<p>but using and EF Lens and extension tubes that have electrical connections, one does not</p>

</blockquote>

<p>With a reverse ring there is no electrical connection between the lens and the tube, thus the camera. <br>

Looks like the idea of turning a good prime lens into macro is not going to work out..</p>

[William Michael]

<blockquote>

<p>With a reverse ring there is no electrical connection between the lens and the tube, thus the camera.</p>

</blockquote>

<p>That is correct, but as I stated I have seen, on a reverse mounted lens, a DIY (do it yourself) electrical connection. It was a ribbon cable from the Camera body to the Lens’s connections. This apparently allowed automatic aperture control. I have not used this rig, only seen it.</p>

<blockquote>

<p>Looks like the idea of turning a good prime lens into macro is not going to work out. . .</p>

</blockquote>

<p>For clarity the thread has been discussion THREE different options:<br /> 1. Using your existing MACRO EF 100/2.8 Lens<br /> 2. Using EXTENSION TUBES on a Prime Lens<br /> 3. Using a REVERSE MOUNTED Prime Lens</p>

<p>Firstly note that using a reverse mounted lens is NOT the same as using Extension Tubes and a Prime Lens <br /> Secondly note that each one of these three arrangements can be made to work for the job you want to do.<br /> But your question was specifically was about Image Quality and you noted it was specifically NOT about how difficult any one of the procedure would be. <br /> I’ve already stated that I think a Prime Lens and Extension Tubes will not be as good IQ as the macro lens that you have.<br /> * <br /> Now, if you are asking a different question, about the IMAGE QUALITY comparison of a Prime lens REVERSE MOUNTED and a Prime Lens and Extension Tubes – then I think that depending upon the Prime lens that you use, in many cases you could/will get BETTER image quality using a Prime Lens Reverse Mounted.<br /> But I still do not think that you will get better image quality than using the 100 Macro lens that you have.<br /> *<br /> If you are asking about ease of operation, then: using Extension Tubes and a Prime Lens or a Reverse Mounted Prime Lens will in mostly all cases be more cumbersome than using the Macro Lens that you have – - -</p>

<p>EXCEPT if you have a copy board set up that you need never pull down and the negatives are consistent such that the copy exposure is consistent. I have used a similar set up “scanning” my Kodachrome Slides using a Rokkor 58 F/1.2 lens; a slide copier and a set of Minolta bellows that I adapted to fit onto my EOS 5D and I set this up on an enlarger stand and used an enlarger head as the light source. The fact that I could keep each exposure constant to reveal the exact exposure of the slide meant that all I had to do was put each slide into the slide copier and release the shutter – the lens stayed at F/11 and the camera’s shutter speed and ISO remained constant. I cannot compare the quality of that set up to doing the same with an EF 100 F/2.8 Lens as although I have that Canon Lens I copied all the slides I wanted to copy, before I bought the Canon Macro 100mm Lens – and the Rokkor 58/1.2 is a very good quality optic and I was happy with the quality of slide copies.</p>

<p>However, you have already noted that your digital exposures are changing to compensate for different negative densities and also that you are copying different sized negatives: so I think that the automation and the flexibility that the EF100 F/2.8 Macro lens affords you and Image Quality it produces, would be the best and also the easiest of those three options for you. And you do not have to buy any other new gear.</p>

<p>WW</p>

[ali_baba2]

<blockquote>

<p>I have seen, on a reverse mounted lens, a DIY (do it yourself) electrical connection.</p>

</blockquote>

<p>Not only DIY, they also sell the reverse rings that bring the contacts around... expensive for what they are...</p>

<p>Anyways for macro vs extension tubes<br>

 

[JDMvW]

<p>For what you'll spend getting the thing set up right so the results are OK, you'll probably spend more money, and certainly more time, than buying one of the decent, not spectacular, to be sure, film scanners like the Canoscan 9000F (often <$200).</p>