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A local jeweller has a Canon EOS 550D with a telephoto lens model 'Canon EF 75-300mm (f/4-56 III USM)' which she's using to photograph her work for sale.

The lens will zoom enough to get large enough images for her purpose, however, the minimum focal distance of this lens is 4.9 feet so she has to take the pictures from across the room.

Is it possible to use this lens for closeup work with an extension tube or screw-in close-up lens, or is it a dead loss for this purpose?

The objects she photographs are typically 2 inches in diameter, and she needs a DOF of 1 to 2 inches depending on the piece.

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I haven't fully run the maths, but my gut feel is that you're going to be stuck for depth of field; at a focal length of 75mm, f/16 and a subject distance of 24 inches, your depth of field is "only" 1.4 inches (according to DOFMaster). Increasing focal length or going closer will reduce the DoF further, which isn't what you want. Of course, DoF is an imprecise measurement (what is acceptable sharpness to you may not be to someone else), but 2" is looking like a bit of a stretch.

I suspect the real answer here is that she's trying to use the wrong kit. For a lot of product photography (i.e. stuff which is going to appear in catalogs, etc rather than being blown up to poster size), you don't need a large sensor - but you do need to get your lighting right. With a light tent, even a relatively cheap point-and-shoot on a tripod will let you get "good enough" product shots for many purposes - and the advantage of the small sensor in a point-and-shoot is that your depth of field is much greater.

  • I agree on the importance of lighting - we tackled that last week. She's ordered some small studio lights with wide-spectrum daylight bulbs. These will free her from waiting for the right ambient conditions. Good lighting will also allow her to stop down a little and improve the DOF. I think the lights will bring the lens issue to the fore. There will be a lot of spill around the light tent, which will cause flare and lack of contrast from 5 feet away. – DavidA Jun 10 '14 at 13:35
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You can get a used EF-S 18-55mm lens for next to nothing from someone trading up from the kit lens and it will solve your problem.

And if you decide you still want macro capabilities it makes much more sense to put extension rings on the 18-55 and not the 75-300 (it will have more DOF, be smaller and easier to use).

Just make sure you get the "EF-S 18–55mm f/3.5–5.6 IS", "EF-S 18–55mm f/3.5–5.6 IS II", "EF-S 18–55mm f/3.5–5.6 III" or "EF-S 18–55mm f/3.5–5.6 IS STM" (not the non-IS I, the non-IS II and not the USM versions) because the older models have a pretty bad reputation regarding their optical quality.

And finally, Philip Kendall is right, lights will make a huge difference.

  • Very minor comment: there's nothing wrong with the EF-S 18-55mm f/3.5-5.6 IS (version 1); it's optically identical to the IS II. – Philip Kendall Jun 9 '14 at 21:16
  • @PhilipKendall - sorry, I'm not an expert in all the 18-55 versions, I was going by reputation and my own faulty memory, I fixed the answer. – Nir Jun 9 '14 at 21:21
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    For what it's worth: non-IS I, non-IS II: avoid. IS I, IS II, non-IS III: optically identical, except that the IS element is fixed in place in the non-IS III. IS STM: best of the lot. – Philip Kendall Jun 9 '14 at 21:27
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Extension tubes don't do much for longer focal length lenses. This is because they add only a small percentage to the lens' already existing focal length. And the 75-300mm f/4-5.6 is such a stinker of a lens to begin with anything you do to magnify it further is just going to magnify its flaws.

What you might want to do is use extension tubes on a shorter lens, where the focal length can be increased by a greater factor than the minimum focus distance. Even one of the more recent 18-55mm kit lenses will work for this purpose, just avoid the early non-IS versions (The non-IS III is also good, but so rare and was only sold in kits in the UK so you'll likely never see one). But the best solution would be to use a true Macro lens. Cheaper extension tubes make it difficult to control/change the aperture from any setting other than wide open.

The Canon EF-S 60mm f/2.8 Macro lens can be had new for less than $500 (US). The EF 100mm f/2.8 Macro lens sells for about $600 new.

In either case it is going to be difficult to fill the frame with pieces of the size you mention in your question and have the depth of field you desire unless you use a narrow aperture that requires plenty of bright, even lighting. Controlling the aperture will be much easier with a true Macro lens than with non-automatic extension tubes.

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Having a little distance between the photographer and the object isn't necessarily a bad thing for this kind of work. Lighting is important and you generally don't want to be so close that you get in the way of the lights. As far as having enough DOF, focus stacking is one way to go , another is to rent a tilt/shift lens which will allow you to change your plane of focus in such a way that having a small DOF becomes manageable. Focus stacking is the easy route, learning how to properly use tilts and shifts is the more difficult, but ultimately more useful in my opinion.

  • +1 for focus stacking, which I was just about to mention =) – Patrick Hughes Jun 10 '14 at 4:06

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