I believe it to be Constantis Gallus, AD 351-354. Soldier spearing falling horseman. Alexandria Mint. I took numerous photos of the reverse. This is the best. Still learning.
I take all my pictures with my phone. About 4-6 inches away. No zoom. It should be clear enough without it when you open them on the computer.
I suspect you're simply too close to the coin when taking pictures. Try backing away just another inch or so (if it is a typical camera phone). Also, stabilize the camera. If it is your phone, just lay the phone atop an overturned glass or other small riser, with the camera lens hanging over the side of course .
Like this. Enlarge the coin with your fingers so it almost kisses the edges of the photo. Then, with the program Paint (or another program) you can join the obverse and the reverse. See here, you can easily see how I put the two photos next to each other.
With a modern-ish phone you should be able to take decent enough pictures. I have an iphone 6 and manage to get passable pictures. Just takes some trial and error.
gsimonel is correct with no doubt but this poor coin has a lump of crud behind the head that looks like it could be the ties of a wreath. Wreaths wear away but the ribbons behind rarely do so it is often better to look at these when decidiing what is on the head. That said, there are always tricks. I have shown this coin here before but those new here can play. I paid $10 for this coin and its surfaces make that double top dollar for such an ugly piece of metal. What do you see that made me HAVE to have the coin? I know I am crazy and I would love to have this coin in the condition it was when struck but it is what it is and it is mine. When I saw it I could not believe it but one second later, I had to have it despite the condition.
What size is it? Looks like this one. Constantius Gallus DN CONSTANTI-VS NOB CAES bare-headed, draped, cuirassed bust right FEL TEMP-REPARATIO soldier spearing Horseman, bearded, bare-headed, reaching, ALEΓ in ex Alexandria 81 A very neat find for sure.
Nice coin - Constantius Gallus falling horseman type. I use my google phone to take my photos. Definitely there was some trial and error involved in getting passable images. I finally learned not to position the camera too close to the coin (which caused some blurriness) and held it back about 8-10" from the coin. Then, with google photos I edit and crop the pictures, expanding them significantly. I find that the detail is retained very well and there is no fuzziness to the images. Good luck with it, as practice makes perfect.
The size of a dime. It's so close I couldn't measure the difference if I hd to. It looks exactly like yours but yours is in much better shape.
There is something in the portrait that doesn't belong there. No it doesn't. The emperor is clearly NOT sucking on a strawberry on the OP.
I also have this coin. At first glance I thought is was the same but upon closer inspection it is different. Same type but a different fallen horseman. This one is cleaner but more worn. I'm finding these ancients are difficult to learn. Too many years with US coins. lol