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

Started Mar 5, 2014 | Discussions thread
Great Bustard Forum Pro • Posts: 40,847
Re: no disadvantage

bobbarber wrote:

If the sensors are equally efficient, then the noise will be the same. Modern compacts using sensors with BSI tech will tend to be more efficient than modern DSLR and mirrorless cameras.

You mean that noise should be the same.

I mean will be the same for equally efficient sensors.

Theory doesn't trump empirical results.

Empirical results echo theory.

For the theory to play out perfectly in real life, then sensors have to be perfectly designed, their can't be any flaws at the level of the the pixels, etc.

They don't have to be "perfectly designed", they just have to be equally efficient for noise equivalence to hold for the same DOF and shutter speed.

My experience, and it's only my experience, is that noise becomes worse at high ISO on all systems than it should, theoretically, so you get a better result at low ISO on all systems compared to high ISO on those same systems than a perfect noise curve tells you you should.

Well, there's no accounting for what you think noise "should" be at higher ISOs, but the fact of the matter is that what the noise is exactly follows what theory says it should be.

We have to distinguish between which system delivers better results and which system is more convenient to use.

Yes. However, systems which are convenient to use may deliver better results BECAUSE they are convenient to use.


Therefore, some cameras belong in both categories, convenient to use, and delivering better results. An example would be compact cameras for hand-held macros of small flowers in distant fields. The convenient camera gets carried more often because it is smaller, gets better results with fewer changes which the shooter doesn't always want to hassle with on the less convenient camera, or have time for, etc.

You're saying if you don't have the camera with you, you won't get the shot. I don't think anyone argues against this. What I'm talking about is the IQ of the photo given that you had your camera with you.

The point is that FF gives you a wider range of options. If these options do not appeal to you, however, then, for sure, you would be better suited with a smaller format unless some other aspect of FF, such as greater resolution, was important.

Resolution should not be weighted on dpreview camera reviews.

What should it be "weighted on"? MTF-50 tests? Sure, FF still delivers greater resolution. Of course, if there's motion blur then that resolution advantage can vanish. Or, more to the point, if we're stopped way down for ultra deep DOF (say, f/32 on FF), then diffraction softening eats away pretty much any resolution advantage one system may have had over another.

Considered, but not weighted. We are at a point where resolution is so much overkill for what consumers need, that it is essentially a non-factor. Read the article on the summary of the CEO interviews in Japan. 6 Mp is enough for a magazine spread. Now we have the GH4 which will take 8 Mp stills at 24 fps indefinitely. Are you better off with the GH4, or the D800 if you are a photojournalist covering a rally and need to capture a critical moment? Oh right, we still need to fork out thousands of dollars for 30+ Mp cameras, because an anonymous dpreview poster needs to print at 200" x 300" and only a certain camera will do. Give me a break. I bet that not more than 1% of the posters here have printed anything, ever, at more than 13x19", which my C8080 still handles just fine, thank you. The vast vast majority of people don't need more than 12 Mp any more than they need to buy a Hummer to drive to the supermarket.

Regardless of what you think people "need", the differences are there. Whether or not the differences matter is another discussion entirely. However, for those for whom the C8080 gets the job done, more power to them.

Particular systems are inherently better than others for particular tasks, and some people find one system to represent a better balance of those factors that matter most to them. For me, even in the case of macro, I find that shallow DOF is often appealing:

You're right, it is a matter of taste, but a lot of the FF low-DOF bluster on these forums is driven by marketing, and "fanboys" (who are often paid shills for different brands--let's be honest)...

"Often"? I see no evidence of that.

...trying to distinguish one camera from another. As I pointed out, trying to get the critical parts of the photo or all of the photo in some cases in focus is a skill, and professional photographers have been doing that since photography was invented. Now certain posters on these forums want to depict in-focus photos as inferior. I like bokeh, but two thirds of the subject should not be out of focus. That's not art. It's an error.

Now you are doing what you accuse the fanboys of doing -- presenting your personal opinion of the matter as fact.

For my purposes, m43 strikes the best compromise. Others might feel differently. I do think that FF wins on noise and dynamic range, and those are good reasons to go with FF.

As I said, the noise advantage of FF comes from using a wider aperture for a given shutter speed, which also *necessarily* results in that more shallow DOF that you are not so keen on.

For example, 50mm f/1.4 on FF has an aperture diameter of 50mm / 1.4 = 36mm, whereas 25mm f/1.4 has an aperture diameter of 25mm / 1.4 = 18mm.  This means that the aperture area for 50mm f/1.4 on FF is 4x as great as the aperture area as 25mm f/1.4 on mFT.  This results not only in 4x as much light falling on the sensor for a given shutter speed, resulting in half the noise for equally efficient sensors, but also half the DOF.

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