Full Frame vs APS-C: Is TOO much bokeh bad? A disadvantage to Full Frame.

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heysavnac Junior Member • Posts: 43
Full Frame vs APS-C: Is TOO much bokeh bad? A disadvantage to Full Frame.

Hi photo community. I have been thinking of switching from a Sony a7iii to a Fuji X-T4 for a couple days now, and mainly the reason is due to the nostalgia I feel from the X-T2 I sold awhile ago, as well as the point I am trying to make in this post. I loved the style of camera (dials and such), and it's creative workflow, though I know moving down to a smaller sensor comes with its disadvantages. but... also, one underrated advantage?

Caution: Very complicated explanation of DOF and Field of View equivalence between APS-C and FF Below. Skip to “ANYWAYS” if you already understand how sensor size and depth of field/field of view equivalency works.

First off lets get something clear: An APS-C camera using the same full frame equivalent focal length, and the same literal aperture as a full frame camera (For example an X-T4 with a 35mm set at F/2 and a Sony A7iii with a 50mm set at F/2) will produce different results optically from the image captured on the Full Frame camera. You will capture an image with a wider (more in focus) depth of field on the X-T4, though the exposure and composition will (or should) be identical to that of the A7iii’s full frame sensor image. (the depth of field and composition on an APS-C sensor with a 35mm set at F/2 is similar to capturing an image on the Full Frame sensor with a 35mm set at F/2, then cropping the image 1.5x in post, to match the field of view and depth of field of the APS-C’s image.) With that being said, the only difference between the 35mm on the XT-4 and the 50mm on the A7iii, both at F2, with the same composition, would be the depth of field. (the exposure will be the same).

A further, yet non-essential explanation for my point:

(Skip to “ANYWAYS” if you now understand the difference of DOF on full frame and APS-C)

Being that the APS-C sensor at its 35mm focal length is compressing the wider “actual” field of view of a Full Frame true 35mm image (remember my example above about adding a 1.5x crop to a Full Frame 35mm lens image), your results will resemble only the field of view [but not the depth of field] of a Full Frame 50mm image, because the APS-C sensor again, is only cropping the composition of a Full Frame 35mm focal length image (which in result, is equivalent to a Full Frame un-cropped 50mm image), but not receiving any less light than a Full Frame sensor at F2. This is why 35mm at F2 on an APS-C sensor will produce a wider (more in focus) depth of field in comparison to a 50mm at F2 on a full frame sensor, even if the focal length appears the same. Because technically, it's like you’re shooting a full frame 35mm F2 lens on the APS-C camera, just cropping it 1.5x due to the APS-C sensor being “cropped”.

Geez that’s a confusing explanation, but it makes sense if you can make it through the tunnel of confusion on this topic. some never make it out. I understand if I could’ve explained it better, but I tried my best. lol

ANYWAYS. my point is, I have noticed when shooting on full frame at F/1.8 (or even sometimes F/2.8), that although I appreciate the amount of light my lens allows my sensor to receive for a quicker shutter speed.. I very often come across the annoyance of not having my entire subject in focus! So why not just... stop down, right? Well, unless I want to raise my ISO and/or lower my shutter speed, I’d rather just keep them the way they are to reduce grain/motion blur. This is why I’m considering a smaller sensor camera like the X-T4. I have taken couples portraits with my Sony A7iii, where only one of the two partners is in focus due to this huge sensor capturing a thinner depth of field where I COULDN’T stop down any further from F/1.8 because we were shooting in very dark light after sunset and my iso was already super high, and my hands couldn’t steady any more for a slower shutter speed. I love the image, but i really wish the partner hugging the other from behind wasn’t so blurred out due to this thin DOF. I believe I would benefit from a smaller sensor because i could still shoot at F/1.8, capture the same exposure, but have more of the second partner in focus.

This, is where a cropped sensor (or even 4/3s) camera would come in handy. In a situation where I need a wide aperture for optimal light gathering, but where I don’t necessarily need (or prefer) as thin a depth of field as full frame delivers to me. Has anybody experienced anything similar or ever thought about this concept? I believe this is what truly establishes an advantage to cropped sensor cameras over full frame cameras, or in other words.. this is a point that presents a unique place for every sensor size in the market, where not one sensor size is superior than the other (when discussing depth of field, not considering ISO Performance or dynamic range). The smaller the sensor, the more in focus.. whilst gathering the same amount of light at identical apertures. F2 will still be as amazing for low light on a cropped sensor as on full frame, but it makes a difference on either sensor depending on the preference of your shooting style. Wether your style requires a thicker wider of field, or a thinner one.

Maybe there is an advantage to smaller sensors? Is there such a thing as too much bokeh, to you? Have you experienced a similar frustration with full frame? Thank you! I’d love love love to hear your responses.

Fujifilm X-T2 Sony a7 III
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