Is an aperture range of 3.5-5.6 shallow enough to provide great bokeh on a cropped sensor?

Question

I have been primarily shooting with a Canon 18-135 f/3.5-5.6 for several years now, and I am not completely satisfied with it. The problems I have are:

1. A bit too wide on the low end
2. A bit too short on the long end
3. Not enough Bokeh (I think, continue reading)

I mainly shoot my kids playing outside, and have occasionally started to take pictures for friends and family (out door shots like the one below).

I am shooting with a cropped sensor, so even though the lens is more like a 28-200, It isn't quite fitting my needs. I routinely wish I had something around a 50-250 (adjusted which is around a 28-150 on a full frame) with great bokeh.

I have been searching around, and the closest I can find is the Canon 18-200 f/3.5-5.6, which at least provides a bit more reach. I find it rather difficult to get a nice out of focus background with my current lens, and I am concerned that 5.6 isn't shallow enough.

From what I understand, if I am shooting with a wide lens then I want to be close to the subject for good bokeh. On a long lens I want to back up, and get the subject far from the background. I try this all the time, but it doesn't seem to work out how I want it.

Am I just shooting with the wrong equipment? Do I need to comprise on focal length range, and just find something with a really large aperture?

40mm f/5 1/200sec

Answer 1

To get the result you want, you need a wider aperture or a larger sensor. If you are already separating the subject from the background as much as is practical, shooting at the lens' widest aperture setting and still not seeing what you want to see then you've reached the limits of you current gear.

At the minimum for longer focal lengths you need an aperture in the f/2.8 or lower range. For shorter focal lengths you probably need a prime with an aperture at f/2 or wider. On your APS-C body I would consider the EF 50mm f/1.4, the EF 85mm f/1.8, one of the 100mm primes, or the EF 135mm f/2 L. If you've just got to have a zoom, the EF 24-70mm f/2.8 L II is an excellent choice but it is pricey. Image quality is virtually identical to the much cheaper 50mm f/1.4 when the 24-70 is set at 50mm, but it is also equally good from 24mm to 70mm. The Tamron SP 24-70mm f/2.8 Di VC is not quite as good, but a lot more affordable and also adds Vibration Control, Tamron's IS equivalent. The APS-C only EF-S 17-55mm f/2.8 IS is also an excellent normal zoom lens, but may be a little short on the long end for you unless you get a separate telephoto lens. For a telephoto lens you should consider one of the EF 70-200mm f/2.8 variants.

For how the sensor size affects Depth of Field (DoF) see this answer. For a comparison of the various 70-200mm options for Canon bodies see this answer.

Answer 2

When trying to maximize bokeh you want to move the subject closer to you and farther away from the background. If the subject is halfway between you and the background (assuming something simple, like a wall and not the scene in your example) and then you move the subject towards you, but then you also move yourself so that your subject is still halfway then you won't see much difference.

This is one reason to get low when photographing animals and children. If you shoot down the background (the immediate ground) is relatively close, but if you get low the background becomes something distant and makes for better bokeh.

Answer 3

You need a much faster (smaller F number) lens. The Canon 50mm F1.8 is very inexpensive and will do a far better job. The Canon 50mm F1.4 is still less than $500 and has what you are looking for. The good news is that while a 50mm is traditionally considered too short for portraits on a full frame camera, with the 1.6 crop factor, a 50mm works well on an APS-C camera.

I rented a Canon EFS 17-55 F2.8 for a wedding and loved it. So much so that I bought one, and now its the lens I use at least 80% of the time.

Answer 4

When trying to achieve a blurred background for a given subject size, and framing, three effects are important:

1. Maximise your aperture (meaning the lowest number)
2. Maximise your focal length (because of the compression the background will appear more blurred)
3. Maximise the distance between the subject and the background

Here you can see a comparison between the long and short end of your lens, and the 50mm f1.8 which is the cheapest option to improve in this area. This graph applies to taking head and shoulder portraits:

http://howmuchblur.com/#compare-1.6x-18mm-f3.5-and-1.6x-135mm-f5.6-and-1.6x-50mm-f1.8-on-a-0.9m-wide-subject

As you can see the long end of your lens can provide substantially more background blur then the short end, but the 50mm easily a lot more.

Answer 5

You should be shooting at f3.5 and not 5.6. The larger the aperture, the shorter the DOF, which is what you are going for. If you cant get it the way you want it at 3.5, you need a lens that goes down to a larger aperture like F1.8 to make it the bokeh more apparent.

Answer 6

I'm not a Canon shooter, so I'm not very familiar with their lenses, but in my own experience I've found that using a macro lens for portraits really helps me induce very pleasing bokeh into the photo without breaking the bank. Of course, I bought a third-party macro, the Tokina AX-Pro 100m 2.8. They may make it for Canon as well (I have the Nikon version). While they advertise it as an f/2.8 lens, the aperture is not constant as it shifts as the lens extends for focusing but the depth of field is much more shallow with that lens than with any other at same depth of field due to the characteristics of macro photography.

Answer 7

Enough bokeh? Yes, especially for photographs such as that pictured. Groups tend to require a moderate depth of field so as to make all subjects in focus. The picture in your question is quite good with the deeper depth of field it has.

Great bokeh? Not really, as the depth of field is not only equivalent to f5.6 - f9 on your crop body (assuming 1.6x crop factor) at the same focus distance, but the lens construction itself also dictates the quality of the bokeh. More aperture blades as well as the shape of the blades change the characteristics and aesthetics of the bokeh. The quality of the lens elements and coatings also affect the image as a whole.

Once you get an f2.8 zoom or wide aperture prime, you will not only have a shallower depth of field, but will also benefit from a consistent exposure across the zoom range.

Having to change your shutter speed or ISO after zooming can be problematic and a pain in the butt. Wide, constant aperture zoom lenses tend to have better construction and optical quality given their overall cost increases.

For portraits, a great yet relatively inexpensive lens is the Canon EF 50mm F1.4 USM, as well as the 35mm F2 and 85mm F1.8. These all clock in at about $300-400 each as are great for shallow bokeh, especially on full frame bodies.

Answer 8

The key is to get as close as your camera will focus. This is the same method if you are zoomed in (likely 3-4 feet focus) or if you are zoomed out all the way (likely 1-3 inches). Obviously the zoomed out 3 inch distance will only work for macro shots. For people and scenery zoom in all the way and get as close as your camera will focus. This works well for a picture of one person but you will not get a group of people.

Answer 9

if your lens 18–135 f/3.5–5.6

Get very close to your model, the closer the better. Keep your model and background as separate as possible by maximizing the background distance. Use your longest focal length (i.e., 135mm) and your widest aperture (i.e. f/5.6). This will produce the most pronounced bokeh your lens and camera will be able to achieve.

I have used a 55–200 VR; at 200mm f/5.6, it creates very good bokeh for head shots.

I have also used a Nikon E-series AI-S 75–150mm f/3.5. At 150 mm, it creates perfect bokeh, the same as my 85mm f/1.8G.

For better results I'm going to buy a 300mm f/2.8. Also, a 200–500mm f/5.6 will give excellent bokeh if you can get close to the subject with a 500mm focal length.

A 20mm f/1.8 will not give better bokeh than 200mm f/5.6. The main idea is to get as close as you can to the subject.

Answer 10

Things that affect Bokeh:

• Size of the sensor
• Distance between you and the subject.
• Distance between the subject and the background.
• Aperture of the lens (wider the better)

As you will have noticed, good lenses with the widest apertures can get quite expensive (especially zoom lenses eg. 70-200 f/2.8).

What you can do as a cheap alternative that could work for you depending on your shooting style and whether your subjects will remain still (as they are in the supplied photo above), is to buy a good condition Helios 135mm f/2.8 M42 lens from ebay for around £30 (plus £15-£20 for a standard M42 to Canon adapter).

It is an old(ish) metal lens built like a tank that is actually really decent considering its price of £30 pounds.

The reason I say about your subjects remaining still is that it's not a zoom lens and it is manual focus only as you are using it on your Canon with an adapter, but it can be very sharp and is very cheap - I have one and I love it.

If you separate your subjects from the background as far as you can and then try with the 135mm f/2.8 with the aperture set to f2.8 I'd be surprised if you didn't get some nice Bokeh.