Potential dead horse: how bad is FF's deep DoF disadvantage?

Started Mar 5, 2014 | Discussions thread
Great Bustard Forum Pro • Posts: 41,999
A few points.

GeraldW wrote:

Back in the days when I was shooting 35 mm film, I sometimes found that achieving very deep DOF was difficult, particularly if a polarizing filter was used, as the small aperture and additional 2 stop loss from the polarizer pushed the limits of hand holding, even with ISO 400 film.

At Yosemite, shooting from Glacier Point, I was trying to get a nearby pine in focus, half dome at some distance, and the mountains in the far distance all in focus. I was shooting hand held and at f/16 the resulting shutter speed was below 1/100 second. It did come out OK, and the resulting print is still on my wall.

Taking that same shot today with something like my G15 would be much easier.

You don't think it would be just as easy using ISO 400 on FF?

I'd also like to take this opportunity for a small rant. There seems to be an obsession with bokeh and separating the background these days. Back when I started this hobby in 1955; a lot more was being written about how to increase DOF, than there was about limiting it. Sure, any text or paper on portraiture discussed DOF and the relation of the background. But for most other subjects, the emphasis was on increasing the DOF.

Then, sometime in the 80's something called selective focus came into vogue. Frankly, I didn't like the look, and still don't.

Whether shallow DOF appeals to you or not is another matter all together. The facts are that wider apertures and shallow DOF go hand in hand, and, as a consequence, to get less noise in low light, people typically use wider apertures which result in a more shallow DOF.

Combine that with the fact that the same amount of light falls on the sensor for a given scene, DOF, and shutter speed for all systems, and that the noise in a photo is a function of the total amount of light falling on the sensor and the efficiency of the sensor, then we can see that less noise in low light for a given shutter speed necessarily comes with a more shallow DOF.

Now DPReview (and others) are showing graphs of equivalent f/# for smaller sensors. I know it relates to equivalent DOF; but, unfortunatly I'm seeing a lot of posts on this site where people are taking those numbers as the equivalent f/# in terms of exposure, and cautioning about the slow shutter speeds that will result. Enough already!

I have never seen anyone say the equivalent f-ratios apply to exposure. But they do apply to the total amount of light falling on the sensor. By the way, you might find this illuminating:


This section will answer the following four questions:

  • For a given scene, what is the difference in exposure, if any, between f/2.8 1/200 ISO 400 and f/5.6 1/200 ISO 1600?
  • What role does the ISO setting play?
  • What role does the sensor size play?
  • What does any of this have to do with the visual properties of the photo?

Overall, this has been an interesting thread.

I'm glad you think so!

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