Extension tubes and depth of field

[eevaa]

Hi everyone!

I would like to shoot objects from a distance of 0.5-2m with my Canon EF-S 15-85mm f/3.5-5.6 lens. I'd like to achieve a more shallow depth of field (think food photography) than I have had so far with this lens. Now I was wondering whether an extension tube would do the trick for me. Are they only used for magnifying or do they influence depth of field as well?

I am still pretty much a beginner in photography, so please keep it simple

 

[scorpion_tyr]

Extension tubes will have a huge impact on your depth of field, and in fact will probably make your DOF too shallow. They don't really magnify anything, they just allow your lens to get much closer to your subject and that decreases your depth of field dramatically. Extension tubes are mostly used for macro work, really small bugs and stuff, but manual focus ones are really cheap ($10 for a set of 3) and even auto-focus tubes are fairly cheap as well ($100 for a set of 3). I would highly encourage anyone to spend the $10 to have some in their kit, but if you're looking at food photography you may find they decrease the focusing distance too much.

There are 3 main ways to shallow your DOF: Zoom in (increase focal length), get closer (reduce focusing distance), and open up your aperture. If you shoot Canon check out the 40mm f/2.8 STM. It's minimum focusing distance is less than a foot, and at f/2.8 it's tack sharp so getting close and opening up aren't a problem at all. Best of all... it's cheap at $200 brand new.

 

[xabit]

I just brought a Kenko set of extension tubes to use with my 50mm f/1.8 prime. Having not done macro before, it's a challenge. Focusing and DoF is difficult. With more experience, hopefully they'll provide decent shots. I couldn't shell out for a macro lens so went with the cheaper alternative for now.

 

[unpopular]

Yes. DOF is made shallower by extension, as doing so decreases minimum focus distance. Longer lenses are suitable for close-focus without excessive magnification.

 

[xabit]

I keep hearing that the best lens to use is a 50mm prime though? What would people here suggest, prime or zoom?

Though I guess you would want a zoom with a wide aperture?

 

[unpopular]

50mm gives you very little working distance. It's great for non-living things because you can get very high magnification without a lot of extension, but you'll need to be up close to the subject, within centimeters when getting much more than 1:1...

 

[Solarflare]

I keep hearing that the best lens to use is a 50mm prime though? What would people here suggest, prime or zoom?

Well, the 50mm prime is "best" because you can create it very compact, since its a so-called "normal" lens, i.e. neither very wide nor very long, and its supposed to be in some way near the natural sight of eyes.

That means 50mm prime lenses, or the equivalent for your sensor size, are typically the cheapest, smallest, most lightweight prime lenses you can get for any camera.

In other cases, they make the most complicated lenses, like the most expensive of all Leica lenses, the 50mm f/0.95 "Noctilux". Leica doesnt offer anything better than f/1.4 for any other focal length. Though Canon offers f/1.2 for both 50mm and 85mm, and then with autofocus.

Its also a very universal focal length for all kinds of applications. A different "school" of photographers prefers 35mm as being even more universal though, like for the Fuji Finepix X100 or the Sony Cyber-shot DSC-RX1.