UncleVanya
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Maybe read this also.
https://fstoppers.com/education/understanding-how-sensor-size-affects-depth-field-312599
https://fstoppers.com/education/understanding-how-sensor-size-affects-depth-field-312599
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Reality check for choice of ISO and f-stop to maximize depth of focus
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New Wrycuda
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If the OP is interested in high resolution, perhaps the Pixel-Shift mode would be worth investigating. With adequate lighting and other sensible settings, a single Pixel-Shift exposure should be possible, and the stabilisation system would also be “otherwise engaged”.
This from DPR review…
One of the eye-catching features of the Sony a7R IV is its 16-image pixel-shift mode. This shoots four images centered around one position then shifts the sensor half a pixel sideways and takes another four, then another half pixel... until it's taken 16 images. These 16 images can be turned into 240 megapixel images (though need to be combined in separate software, unlike the systems from Olympus, Ricoh and Panasonic).
New Wrycuda
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What you are actually doing is partially compensating for the poor choice of focal length with that 20mm wide angle lens.
Some buttons are toggle (On/Off).
Better not. Fstopers is probably the worst photography website for anything "technical". Photographylife and Cambridge in colour are head and shoulders above it. He says
The pixel density makes no difference to DoF, but viewing conditions certanly do. True that, but then he says
Any DoF calculator will verify that this is wrong.
He just changed the viewing conditions for one of the images to make this happen! It was not visible before because it was not true.
Cropping changes DoF. If people don't understand that and think that DoF remains the same as you crop the image, they don't understand what DoF is - it is a property of the displayed image under normalised viewing conditions.
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Wannabetoo
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Many thanks for your further comment. Yes, I think the a7R's stabilization feature is turned off, for the reason you mention (advice that Sony thankfully included in their tiny 700+-page manual for this camera), but thanks to your comment, I will check!
DavidWright2010
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Given the clumsy way that Sony implemented pixel-shift, I wouldn't want to process hundreds of images with it. I did do a 4-image stack of my test rock (3 inches long) with my Olympus E-M5Mk3. The full image was 28MB - here's a half-sized version:
Olympus pixel-shift focus-stack
David
Wannabetoo
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Many thanks for all this. Looks pretty good!
But I continue to stand with my eyes (so to speak). Perhaps it's because we always look through the single lenses of our eyes at any one time, and even though we can of course change their focus, I'm thinking we have an intuitive sense of how things look through a single lens. For me, this is especially important for the intentionally close-up shots I've been taking, to give a sense on intimacy.
In any case, I remain very grateful to all, for all comments.
But I continue to stand with my eyes (so to speak). Perhaps it's because we always look through the single lenses of our eyes at any one time, and even though we can of course change their focus, I'm thinking we have an intuitive sense of how things look through a single lens. For me, this is especially important for the intentionally close-up shots I've been taking, to give a sense on intimacy.
In any case, I remain very grateful to all, for all comments.
New Wrycuda
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-With the possible exception of those who tell you that a 20mm FF lens is the wrong choice.
Wannabetoo
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My thanks again for everyone's comments.
For the record -- and in case of benefit to anyone else -- I've tentatively concluded that this approach should work (given my equipment and preferences), except that to additionally address some subtle environmental vibration, I should set the ISO as high as possible (i.e., without unacceptable graininess), which from experimenting to date, is ISO 640 or 500. But I've also realized I need to be careful not to violate the minimum focus distance, which for the Sony a7R IVa and Sony 20mm f/1.8 GG lens is 19cm in auto focus and 18 cm in manual focus (from the sensor, as marked on top of the camera).
Your comments helped me get this far, and for me, this is a major advance!
For the record -- and in case of benefit to anyone else -- I've tentatively concluded that this approach should work (given my equipment and preferences), except that to additionally address some subtle environmental vibration, I should set the ISO as high as possible (i.e., without unacceptable graininess), which from experimenting to date, is ISO 640 or 500. But I've also realized I need to be careful not to violate the minimum focus distance, which for the Sony a7R IVa and Sony 20mm f/1.8 GG lens is 19cm in auto focus and 18 cm in manual focus (from the sensor, as marked on top of the camera).
Your comments helped me get this far, and for me, this is a major advance!
Why? I assume, that you shoot from tripod, so you can set "maximum quality" - ISO100.
Maybe you can experiment with macro rings to get better minimum focus distance.
Wannabetoo
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To clarify, given my equipment and aesthetic preferences, I'm concluding I should maximize the depth of focus by (1) using bright light; (2) minimizing the aperture (by physically setting the lens to f/22); (3) setting the ISO as high as possible (i.e., without introducing unacceptable grain); and (4) using the camera's Aperture priority mode to let the camera set the shutter speed but using bright light, (5) being prepared to reduce the exposure as needed. 
Not relevant to depth of field. But yeah, good light is necessary to show details of the rocks
Yes, but you will loose details because of using such high aperture.
Why? Nonsense.
Tripod, aperture priority, ISO 100, let the camera choose the shutter speed, use exposure compensation if needed.
(5) being prepared to reduce the exposure as needed.
New Wrycuda
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This is crazy stuff, and you appear not to have absorbed any of the valuable advice that has been contributed. -Or is this a joke?
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dsjtecserv
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Little to none of that is consistent with the advice you have been given in the numerous posts above. You are setting yourself up for a suboptimal result. Here is a summary of what would give you the best results:To clarify, given my equipment and aesthetic preferences, I'm concluding I should maximize the depth of focus by (1) using bright light; (2) minimizing the aperture (by physically setting the lens to f/22); (3) setting the ISO as high as possible (i.e., without introducing unacceptable grain); and (4) using the camera's Aperture priority mode to let the camera set the shutter speed but using bright light, (5) being prepared to reduce the exposure as needed.
- Use a tripod and a cable release or delayed shutter, or both. doing that, a slow shutter speed can be used.
- Since a slow shutter speed can be used, there is absolutely no reason to increase ISO. Use base ISO of 100.
- Use a longer focal length. A 20 mm lens will require you to either have your subject rock be small within the frame (thus with fewer pixels on it and less detail), or else you will have to be very close to the subject, which will misrepresent it with distortion and will provide no advantage for depth of field.
- Use a mid-range aperture. F/22 will not give you optimal depth of field, because diffraction will make the entire picture blurry, counteracting the DoF. F/8 to at most f/16 will provide the best combination of depth of field with minimal degradation from diffraction.
- Don't peremptorily reject focus stacking. This is exactly the tool that an experienced photographer would use for this case, where faithful portrayal and detailed reproduction of the subject are priorities. You can reject that for esthetic reasons if you want, but recognize that you are compromising the objective you stated at the beginning of the post.
Dave
Diffraction will compromise image quality.
ISO doesn't "introduce grain" or noise.
Setting a goal of reducing exposure as much as possible guarantees poor image quality. But it's your project. Good luck.and (4) using the camera's Aperture priority mode to let the camera set the shutter speed but using bright light, (5) being prepared to reduce the exposure as needed.
Wannabetoo
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Many thanks for your thoughts.
Please forgive me; in this attempt at a wrap up, I meant to add that my circumstances include some mysterious, unsensed vibration, which shows up in photos longer than a second or so. (The camera's "SteadyShot" feature is set to off, so that can't be the problem.) This is despite a concrete floor. Perhaps it's from vehicles on the street in front of our house, where there is also a stop sign.
My solution is to increase the ISO, though as little as possible, without introducing grain.
Thank you for suggesting I consider macro attachments. The Sony 20mm F/1.8 GG lens is so effin (another accidental pun!) glorious, I hesitate to insert anything in the chain, but thanks to your suggestion, I'm planning to look into it.
Here's to all y'all!
Please forgive me; in this attempt at a wrap up, I meant to add that my circumstances include some mysterious, unsensed vibration, which shows up in photos longer than a second or so. (The camera's "SteadyShot" feature is set to off, so that can't be the problem.) This is despite a concrete floor. Perhaps it's from vehicles on the street in front of our house, where there is also a stop sign.
My solution is to increase the ISO, though as little as possible, without introducing grain.
Thank you for suggesting I consider macro attachments. The Sony 20mm F/1.8 GG lens is so effin (another accidental pun!) glorious, I hesitate to insert anything in the chain, but thanks to your suggestion, I'm planning to look into it.
Here's to all y'all!
Wannabetoo
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To Bill and all other most recent commenters, if interested, please see my most recent comment above, explaining why I've found I must unfortunately avoid long exposure times.
For what it's worth, I'm surprisingly pleased with the results so far, though I'm still stumbling with the controls. (Gaaaa!)
But I'm truly grateful for all comments. Even if I seem to be ignoring any of them, all have helped deepen my understanding.
For what it's worth, I'm surprisingly pleased with the results so far, though I'm still stumbling with the controls. (Gaaaa!)
But I'm truly grateful for all comments. Even if I seem to be ignoring any of them, all have helped deepen my understanding.
New Wrycuda
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Is the subject on the same floor? Any seismic activity in your area?
Macro rings wouldn't help much in your situation, but be aware that they have no optical elements, and just change the distance between the lens and sensor.
Why do you need such long exposure? I thought that you have lighting installed.
Wannabetoo
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Thanks for asking about seismic activity. We're supposed to get The Big One some year soon, but meanwhile, no reported activity. We're at the top of a small hill, adjacent to an intersection, and the soil is a jumble of basalt cobbles in a soup of wet clay soil, and while I'm not a geologist, I can imagine some subtle shock waves emanating from passing vehicles.
And thank you especially for helping me understand macro rings. I must indeed look into them.
And thank you especially for helping me understand macro rings. I must indeed look into them.
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