Achieving maximum bokeh on DX camera

[aaron_lucas]

<p>Hi!<br>

Is it possible to get the same amount and quality of bokeh as FX cameras on DX cameras? What prime lenses should I use to get the maximum bokeh? Can it be done using image editing softwares?<br>

Thanks</p>

[Matthew Currie]

<p>Depth of field depends on focal length, distance and aperture. To get the same field of view in DX as you would in FX at the same distance requires a shorter focal length, so you're going to lose some bokeh. If you want to gain it back, you must either increase aperture (get a faster lens) or increase focal length.</p>

<p><br /> The amount of 'bokeh' depends essentially on depth of field, and the quality of the lens. I don't have any experience with software. I am not obsessed with bokeh myself.</p>

<p><br /> If you put a 35 mm. lens and a 50 mm. lens on a DX camera, and frame your subject the same, you will be further away with the 50, and that increase in distance will increase depth of field, but it will still be shallower than the DOF of the 35. It will also, of course, change the amount of background that is shown (see the family of angles thread below). So "bokeh" can be increased by using a longer lens, but is obviously limited by how far away you can get from your subject, and what perspective view is required between the subject and the background.</p>

<p>Here is a shot I did some time ago, in which I framed a subject more or less the same, using a 35 mm. lens and a 50 mm. lens on the same DX camera. The right hand 50 shot is, of course, from further away. The aperture in both cases was 2.8. As you can see, the right hand image, from the 50, has a blurrier background (you can see it especially in the framed picture on the shelf), and also shows the decreased angle of view in the perspective.</p><div></div>

[paddler4]

<p>If what you mean by "bokeh" is minimizing depth of field, the best explanation of sensor size and DOF I know of is this: <a href="/learn/optics/dofdigital/">http://www.photo.net/learn/optics/dofdigital/</a></p>

[SCL]

<p>Strictly speaking, "bokeh" is a function of aperture and lens design. It is defined as the "quality" of out of focus areas in a photo, not the quantity. Many less experienced photographers mistakenly refer to out of focus areas as "bokeh", which isn't the case. So, if you're talking about out of focus areas instead of the quality of out of focus, what Matthw said above is generally right on target. The point I would add is that if you really want lots of out of focus areas, you can achieve this most easily using a wide aperture lens...in the 50mm group you would typically be looking at f/1.4 or if you could afford it f/1.2, in the 90mm group you would typically be looking at f/2 or so to achieve most impressive results. You also want to use high quality lenses (read expensive) for best results because since you are shooting at wide apertures, you want the lenses to be especially well corrected for other types of optical distortions which are most noticeable at wide apertures. One of the downsides, though, is that the plane of focus can be very narrow...in some cases 1mm or so, very hard for most people to achieve without a tripod, excellent eyesight (for manual focus lenses), or well tuned bodies using AF lenses.</p>

[Wouter Willemse]

<p>Which lenses do you have today, Aaron?<br /> Getting a very shallow depth of field is easier with large apertures, but at close distances, also small apertures as f/5.6 or f/8 can be shallow enough, as Matthew explained very well. So, it may help to understand what lenses you have today, and maybe an example of what kind of photo you are trying to achieve. That could make it a lot easier to answer you in more detail on what kind of lens would do the trick on DX.</p>

<p><em>Plus, as Stephen wrote, bokeh is something else, it cannot be 'a lot' or 'a little', only 'good' or 'bad'; it's a frequently misused term. What you refer to is depth of field (DoF). But even if many do it wrong, still better to learn the correct term.</em></p>

[mukul_dube]

<p>For less depth of field: 1. Longer focal lengths better. 2. Wider apertures better. 3. Short camera to subject distances better. 4. Greater separation between subject and background better. Wouter is right about using the correct words. A DX camera will always give more depth of field than a FX one because it is the focal length which counts, not the angle of view.</p>

[bobatkins]

<blockquote>

<p>The amount of 'bokeh' depends essentially on depth of field, and the quality of the lens.</p>

</blockquote>

<p>This is a common misconception assuming you are relating "amount of bokeh" to "amount of blur" in a quantitative sense. Depth of field and the amount of background blur are very different things and the relationship is quite complex. DOF tells you what will look sharp. It says very little (if anything) about how blurred anything outside the DOF will be or how it will look. So DOF and Boken describe two completely different regions.<br /> <br /> I cover this in some detail here - http://bobatkins.com/photography/technical/bokeh.html and in even more detail (with a calculator) here - http://bobatkins.com/photography/technical/bokeh_background_blur.html<br /> <br /> In the far field case, i.e. with the lens focused at a "normal" distance and the back ground well beyond the far limit of the depth of field (e.g. at infinity), the background blur is actually a linear function of the physical aperture (focal length/fstop).</p>

<center><img src="http://bobatkins.com/photography/technical/bokeh/compare2.jpg" alt="" width="610" height="311" /></center>

<p><br /> So to get the maximum infinity background blur for a portrait, you'd want to shoot it with a 600/4 lens. That would blur infinity 3x more than if you shot the same portrait with a 50/1.0 lens, even though the 50/1.0 would have a much shallower depth of field. The 50/1.0 would blur things<strong><em> near to</em></strong> the subject more than the 600/4, but the 600/4 would blur things<strong><em> far from</em></strong> the subject more than the 50/1.0 (assuming we're shooting wide open).<br /> <br /> The simple answer to your question is that you want the largest physical aperture you can get along with the fastest relative aperture. For an affordable lens that usually means an 85/1.8 or 100/2 for portraits. a 50/1.4 will give you less depth of field, but won't blur distant background quite as much. Going shorter and faster gets more expensive, as does going longer and faster. The 50-200mm region usually give you the "best bang for the buck" in terms of shallow DOF and maximum background blur, with lenses from a 50/1.4 to a 200/2.8. An 85/1.2 is about the best, but it's expensive.<br /> <br /> Running the numbers through a <a href="http://bobatkins.com/photography/technical/bokeh_background_blur.html">DOF/background blur calculator</a> is the only way to know what works best. It's not something that's intuitive or has a simple answer for all conditions.<br /> <br /> The very short answer to "Is it possible to get the same amount and quality of bokeh as FX cameras on DX cameras? " is no, it isn't, not with the same lens or angle of view shot at the same aperture. That's one reason people use full frame. With Photoshop and enough work, you can probably simulate it though.</p>

[James G. Dainis]

The out of focus background in the 135mm photo on the right is what is called nisen bokeh. The out of focus lines almost seem to double. The nisen bokeh in that photo is not too bad but it does make the photo look a bit funky. That is one type of bokeh to avoid, not to wonder how to maximize it, unless for weird artistic effect.