Photograph poster slightly from side but retain all-over sharpness?

Question

Using a Sony Alpha 7 III (Sony lens 24-240mm), I want to photograph posters and bigger signs outside. For stylistic reasons, as well as to avoid reflecting myself in the occasional glass, I do so sometimes slightly from the side. How would I retain the best overall sharpness of the full poster without a tripod?
If I choose A (Aperture Priority) mode to dial to a higher aperture for bigger focal field, the shutter time is increased to retain light, which seems to increase blurriness a bit. If I choose AUTO mode, or set to a lower Aperture, the Shutter speed is fine but I only get super crisp sharpness in one place of the poster. (While I don't plan to carry a tripod, if that's the only solution, I'd appreciate knowing that too. Same for using a flash light.) I've also played around with different ISOs in A mode, but the picture quality still lacks crispness. Thanks!

Bob Macaroni McStevens · Accepted Answer

Options
No additional equipment methods

Stand further away and use the zoom to frame the subject(s). At a given aperture, a longer focal length "lens" will provide, in absolute terms, a deeper depth of field. In terms of linear perspective this is a change to the station point. This will also have the effect of reducing linear perspecive distortion in the picture because a more distant station point makes angle between the flat subject and the lens axis closer to a right angle.*

In manual mode, set the aperture small enough to provide adequate depth of field + raise the shutter speed fast enough to reduce motion blur + and increase the ISO high enough to provide an adequate exposure. Higher ISO's may generate more noise than is acceptable for your use. Or it may not.

Additional equipment methods

In aperture priority mode, use a tripod.

In aperture priority mode, use external light sources under your control.

Swap out the lens for a tilt shift lens. Rotate the lens so that it provides front swing instead of front tilt. Adjust the angle of swing and aperture to capture the receding subject plane in acceptable focus.

Remarks
Making the picture you want will often require tradeoffs. Often one of those is additional work (e.g. using a tripod). Another common tradeoff is money (e.g. tripod, lights, tilt-shift lens). If the picture matters enough, then the work is worth it. If it doesn't matter enough, then it isn't.
Sometimes making the picture you want means exploring similar but different pictures (e.g. changing the station point). Personally, if I am trying to make a picture in "street style" I will use high ISO as a natural part of what I am trying to capture.
Often, making the picture you want will involve social risk (e.g. what will people think of me using a tripod in public, the creepiness of taking pictures across a busy street with a long lens**). For me, this is the hardest part.
Footnotes
*You could also use a shorter focal length (wider angle) "lens" from the same distant station point and then crop in to the subject of interest. The loss of absolute resolution might or might not be acceptable for your needs.
**Using a tripod for long lens shots across a busy street is probably less creepy than hand holding because it's slower and more obvious. This makes it less likely for people to assume you are trying to get away with something. And it gives people time to ask questions as you go about your business.

Tetsujin · Answer

I don't know the Sony specifically, but if you're using Aperture priority mode you should be able to manually set ISO higher, thereby reducing exposure time & therefore camera shake.
You may need to experiment with different ISO settings until you discover the best trade-off between exposure time & noise (apparent graininess) in the resulting image. My own camera, though it goes up to 25600 for ISO, is actually usable to easily 4000. By 8000 it's getting too noisy for me, but I don't think you'd ever need it that high even in very muted daylight.

Solomon Slow · Answer

You're saying that motion blur becomes a problem when you choose an aperture that's small enough to give you the depth of field that you want. There's a couple of things you can do about that;

Put (or wait for) more light on the subject, or
Put the camera on a tripod, or if neither of those is portable enough for your "street" photography,
you can always try using image stabilization (IS).

Image stabilization (either in the lens or in the camera body) is not a magic silver bullet, but it definitely can help—sometimes it can help a lot.  Does your equipment support image stabilization?  Do you have the IS option turned on?

Zeiss Ikon · Answer

Another option besides stopping down: it may not give you as much side view as your example above, but will get you and your camera out of the reflection in the window: a shift lens.
Essentially, this lets you set up a square-on shot, but offset to the side.  The depth of field requirement will be very small (because the subject can be parallel to the sensor plane).
If you need the keystoning for compositional reasons, you need, instead of a shift lens, a tilt or swing lens -- this will allow angling the plane of focus so it's no longer parallel to the sensor plane, allowing you to control the perspective by camera position, but keep an entire plane, not perpendicular to the view axis, in focus.
These movements are the norm for large format view cameras and a few medium format cameras built to act like them -- film cameras, that is.  A common view camera (like my 1940-ish Graphic View) will have rear rise and tilt, front rise, tilt, swing, and shift, and the ability to angle the focusing rail as well to get more movement in a particular direction if needed.

Photograph poster slightly from side but retain all-over sharpness?

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