Getting all elements in focus

Started 2 months ago | Discussions thread
lokatz Senior Member • Posts: 2,448
Re: Getting all elements in focus

Simon van Wijlen wrote:

Hi all, two weeks ago I upgraded from a 7D to R6. Took me a while to figure the settings out and 'automate' things in my head, but sofar so good.

Hi Simon,  Glad you're making progress. I hope you won't mind me observing this, but it looks as if you are still learning photography, so I will make some general observations.

One burning question remains : on the 7D I could easily get "everything" in a scene sharp by going to the "max" F value of a lens.

Doing so is actually a bad idea with any lens.  You are correct that at the smallest aperture (what you refer to as the max F setting is actually the min F setting since the way these values are given is f/22, for instance, which is a lot smaller than f/4 or f/2.8 where the lens might be 'wide open'), lenses have the widest depth of field such that 'everything' in the image (well, at least from the lens' closest focusing distance to infinity) CAN be in focus if you pick the proper focusing point.  So this would be a good thing, but only if the resulting image is sharp.

Problem is, when fully closed up, at f/22 or whatever the minimum aperture for a given lens is, the image will be anything but sharp. This is because of an optical effect called diffraction that makes your images blurrier the smaller the aperture gets. It kicks in early but is definitely pronounced from something like f/11 or f/13 for most lenses.  As a matter of fact, almost all lenses are at their sharpest (= deliver the highest resolution) at half their widest aperture and below, so an f/4 lens will be sharpest at f/8, often below that, and an f/1.8 lens usually reaches its maximum sharpness at f/3.5 or so.

So what are you as the photographer to do here?  The answer is 'find the best balance between depth of field and lens sharpness'. Experienced photographers hardly ever use apertures smaller than f/11.  That's because the loss in sharpness if you 'stop down the lens' (close its aperture) further is significant, whereas the gain in depth of field is not.

If you have never done that, play around with a depth-of-field (DoF) calculator such as this one,  and compare the results for your 7D (digital camera with crop factor of 1.6) and the R6 (35mm full-frame) by entering the focal length and varying  aperture and focus distance. This will give you an idea of two variables:

1. Where should you focus?  (Hint: select an aperture setting in the DoF calculator, then vary the focusing distance.)  This will help you the find the best focusing distance, which is the one where the nearest acceptable sharpness distance is as close to you as possible and the farthest one just reaches infinity, assuming you want everything all the way to the horizon sharp.

2. How big is the difference if you make the aperture smallest, say f/22, versus only small, say f/8?  You will find that it is usually not very big. For instance, with a 50mm lens on your R5, if you pick the optimum focusing distance of about 3.7m (12ft), everything from 1.82m (6ft) to infinity will be reasonably sharp.  If you pick f/11 instead, the optimum focusing distance is now 7.2m (24ft) and the reasonable sharpness range goes from 3.59m (12ft) to infinity.  This may sound like quite a loss, but the difference in the near distance won't matter in most shooting situations, whereas the overall image quality will: your image will be quite a bit sharper at f/11 than at f/22, and even better at f/8.

Conclusion: DON'T make the mistake of using very small apertures, and DO figure out what the best focusing distance is, i.e., where to focus. (Hint: the DoF calculator allows you to calculate the ideal distance for any shot.  Practically, using a distance that is roughly double that is a good idea: this means you will give up a small amount of sharpness in the front of the image but everything will definitely be sharp all the way to infinity.)

When I do that on the R6, even with high ISO boundaries, the camera quickly slows aperture down to 1/30 etc. I'm using a canon 24-105 L macro, was taking photo's at F22.

I ASSUME (since you don't say) that you are using the same lens on both bodies, and that you meant to say 'shutter speed' instead of 'aperture' here? If so, I would find this somewhat puzzling since the same lens at the same aperture will allow the same amount of light on the sensor, so I suspect there are some camera settings that are different.  In any case, it should pretty much be a don't care once you stop using f/22, since that allows you to pick significantly higher shutter speeds.

I know this is a very basic photography thing, but how do I get 'everything' in a scene in focus / sharp?

Hope the above explanations help you figure this out.

Reason for asking here in this Canon R forum is because I think with my 7D this worked better than now with the R6, same trick but the 7D wasn't slowing down the aperture in my recollection as much as the R6 now did.

Again, shutter speed can be slowed down, aperture can not.

In the end the pics were still useable as the scene had mainly sitting people without too much movement and I guess I had a steady hand... using a denoise tool cleaned the pics up to a useable level. But still, I'd like to learn how to do this better.

... and that's the right spirit.  Have fun doing it!



Hope this helps a little.  Lothar

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