Working distance of EF 100mm f/2.8L

[RobertCampiin]

I would greatly appreciate it if someone could tell me the working distance to the front of the lens of the 'L' version of the Canon 100mm EF macro lens, i.e. 100mm f/2.8L when at maximum magnification of 1:1.  Unfortunately, various on-line reviews of this lens list its working distance at 1:1 as 13.2 cm, 13.3 cm, 14.0 cm, 14.6 cm, and 14.9 cm.  It turns out, I only have 13.9 cm to work with, so the precise working distance at 1:1 matters.  Yes, I'm aware of the Canon 180mm macro, but its nearly 30-year-old design has lower resolution than the 100mm 'L' that was designed more than a decade later.  Thanks in advance for your help.

[RobertCampiin]

Thanks for taking the time to respond, but working distance is only part of the problem.  The other is the resolution of the lens.  Unless it is at least as great as that of the camera's sensor, information is lost.  Unfortunately, the sites you link to for the Sigma lenses use statements like "great image quality," rather than something that's actually meaningful like MTF or lp/mm.  And a lens doesn't seem like "incredible value" when the buyer has to send it back at least twice because of functional issues, which was the case at one of the sites you linked to.  For your use copying slides, a lens with acceptable working distance and 1:1 magnification are necessary, but so is resolution at least as good as the film or camera, whichever is lower.

[spencerselvidge]

My sidebyside tests have been stellar on my R5 with the 70mm Sigma ART vs Canon EF 100L, especially into the corners at full 1:1. The 70mm is far superior. Closer to my Nikkor-Scanner lens than the Canon. I have not tested the RF mount version, though I have read its very similar to the EF. 

I am not only doing 35mm slides, was just an example. I usually image flat objects at 1:1 though. Lots of people have tested many lenses on silicon chips, showing fantastic performance.

If you want to create your own data, you could buy 35mm/120 resolution targets to test your lens resolving power on your sensor as well. If interested, I can link you to some. I use them in various sizes. Regardless of your use case, this could be useful data for you if it is of serious concern. 

Newer lenses will be designed with modern sensors in mind compared to old ones. Personally I will opt that direction when given the chance but there are even more amazing performers in old and modern copy and reproduction lenses. It is quite the rabbit hole initially but there is a wealth of info out there. 

On the Sigma that was returned... as best I can tell it was because of the OS system they use. Seems it requires the OS to be "off" when installing and removing the lens. Plus for me, it would never be on because it is used on a tripod or in a well-fixed position. 

Happy to chat more and hope you find what you're looking for! Good luck 

[spencerselvidge]

https://www.sigma-global.com/en/lenses/a018_70_28/specification.html

Found a chart. No lp/mm but MTF. 

[RobertCampiin]

Thanks for taking the time to write.  However, it may (or may not) have "fantastic performance," but Sigma only shows the MTF at 10 and 30 lp/mm, the latter being approximately equivalent to a 7 Mpixel sensor.  For the camera's sensor to be the limitation, the lens has to resolve over 100 lp/mm.  I need all the resolution the camera has to offer, so the only recommendation that I can rely on is the performance of a lens as measured by a reliable source.

[RobertCampiin]

When I wrote "the only recommendation that I can rely on," I should have added "for purchasing a lens."  I am able to measure the resolution myself, but I'd like not to spend the money to buy a lens that someone says has "amazing performance," only to find it actually is somewhat lacking in amazingness. 

[spencerselvidge]

Understood. Data is king, but its is hard to acquire! Haha! As I understand it, and I could be wrong, most MTF tests are usually done at infinity. Macro lenses are not optimized for infinity but unfortunately commercial producers rarely change their tests to account for this and measure them at infinity anyways. So test targets (Vlad's Test targets on Adox 20 film or specialty targets from Edmund Optics, for example) and info from other enthusiasts who dig deep into this will show us more than manufacturer marketing typically will ... unless the manufacturer provides 1:1 MTF data. 

So I will leave it here with this advice because I recently spent months similarly researching as well:

Definitely look into the lp/mm of lenses optimized for 1:1 rather than lenses with the ability to get to 1:1. Lenses like a Printing-Nikkor 105mm 2.8 (Rayfact still produces similar), a Schenider Macro-Varon 80/4.5 (now called Pyrite), or one of the Rodenstock Rodagon 75mm f/4 printing/duplication lenses. They all have variations/options and there are more specialty lenses from various makers from there. They are, in my anecdotal experience with them borrowing from friends, a measureable notch above anything from the major full frame camera makers. 

Some data can be found from their makers (due to their optimization use case) and on some specialist forums having to do with macro and micro photography. Which is how I found the link below. It has some independent data collected at 1:1 for many lenses (including MTFs and working distances). Though outdated in web design, it has useful features like building comparison charts.  https://coinimaging.com/macro_lens_tests.html 

Personally I am adapting my Coolscan 8000 Scanner-Nikkor lens for now until I can afford/justify a Printing-Nikkor 105 or 150 or a Macro-Varon 80. 

Good luck to you on your project! 

[spencerselvidge]

https://medium.com/on-film-scanning/vibration-proof-scanning-setup-is-your-rig-up-to-the-task-ffa4f5... I remembered this post, with test targets and lp/mm conversation. There are test images with the USAF Test Target info for the Sigma 70mm and APO Rodagon 75/4 across many apertures and shutter speeds. Might become useful for you. Thats all, cheers.