He's been hitting the gym, so now the anatomy and animation should be somewhat clearer. Defining each body part has helped me get a better idea of exactly what's going on.
The new vertical motion feels more natural for this sort of stride. Personally though, I think I would've made the stride a little larger instead - the character lifts their knees a lot and it seems like a rather brisk walk, so the small stride isn't the most intuitive match for it.
In the latest version, I've made the full extent of each arm reach about halfway across the thigh at its furthest reach on the 5th frame, and halfway across the lower leg at its furthest reach back on the 1st frame. I'm starting to think it looks a little weird how his hand flicks forward by a pixel between the fourth and fifth frames. Anyway, here's an image with red dashes to indicate how far the arm is swinging - do let me know if you'd suggest increasing it by a pixel or so on each side to match the stride better:
I'm afraid I don't see the bending of the feet.
Yeah, it was very minimal. Hopefully it's more visible in the newest version.
The elbow doesn't bend enough still.
I suspect that's still the case. I'm having a surprising amount of difficulty drawing a more pronounced bend. I'll see what I can do though.
The swing feels too fast when moving backwards. I think the problem is that you're animating the arm as forceful intentional motion rather than as a pendulum swing that slows down as it reaches the extremes and is at its fastest in the middle.
I've made the swing move fastest in the middle both ways, and only by a pixel at each end of the arc. I can't currently detect any unnecessary speed in the back swing, so hopefully that seems fixed.
(Also, I think the arm might be a little too short?)
Yes, I think the arm was a little too short - I'm fairly confident the new proportions are more suitable. To be honest, I think the head on the most recent version looks a little large, but it seems to match up with references.
The legs move forward very quickly, perhaps slowing that down might help? Rather than move the existing frames though, consider adding some extra frames, to slow the walk down overall. That should help with the small strides not matching the fast movement speed.
I'm determined to do this on just 8 frames, particularly with regard to future efficiency. When I get something I'm happy with, I'd like to use it as a template for other characters. I have tried slowing the frame rate by 25%, however. It's interesting to see it at this speed - the legs still look okay to me, but there might be something I can't quite identify going on as his arm moves back, over frames 7, 8, and 1:
The arcs aren't bad, but they could be a bit more exaggerated on the arms and the feet could "drag" a little as they're coming forward.
I'm trying to avoid an exaggerated, cartoony look, but I'll give this a go. Do you think it would suffice to move the arms about a pixel further forward and back both ways?
The feet could "drag" a little as they're coming forward.
What would it mean to make the feet drag as they move forward? Would I slow down the rate at which they move forward slightly for the first few frames, then allow it to speed up for the last ones?
To reduce the "robot" feel, you might want to bring the shoulder back a bit more as it moves back and emphasize a little more "twist" in the hips and shoulders. Right now (leg-wise) it's like he's walking on stilts (i.e. waaay too "vertical" of an action-line), which feeds into the "brisk robot walk" problem.
The shoulder has a horizontal range of just three pixels in this version (i.e. it moves back just one from its starting position, and forward just one). How many pixels would you suggest increasing it to? His hips don't move much at all either. They move forward one pixel, then back again. About how far would you suggest they move?
Also, would it also make sense to have him leaning forward slightly, or does that not happen noticeably at this resolution when someone is walking casually?
Once you figure out the side-view, only then should you really aim at the back view. However, at least the back view doesn't read too poorly except for the (our left) arm, and some strange "popping" of the shadow of the (our) right elbow from the back view.
Yes, I'll just focus on the side view for now.