Originally 持っている means to hold or to possess something, whereas ある means to exist. So, when a speaker talks about if he has something with him IN HIS HANDS, both 持っている and ある can be used in the same way. For example: ここに名前を書いてください。 ペンは？ 〇持っています。／〇あります。 When to say a speaker has something with him, which he can't grab with his hands, only あります can be used. For example: 電車で帰りますか？ 私は、　〇車があります／×車を持っています　から、車で帰ります。 When to emphasize that a speaker owns something, 持っている would fit more than ある. For example: 家を持っています。 （I own a house.) 家があります。 （It could be a speaker's house or a rented house.　It sounds like at least a speaker has at a place to go back to.) ここで写真を撮りましょう。 カメラは　〇ありますか？／〇持っていますか？ カメラは　〇あります。／〇持っています。 However, about your example sentence, as Ayano-san explained, 私はカメラがあります is a bit awkward to me too. It might sound like a camera is a part of a speaker. It's better to say カメラはあります in response to カメラは（ありますか）？. This is a good but a difficult question to answer, but I hope this helps!

Please let me write a reply to your comment here. (Q)You said: 家を持っています。 but one can't grab a house with his hands, as it happens with the car. How can then this example be correct while the one about the car is wrong? (A)Both 持っている and ある could have two meanings: to possess and to hold or to have something with a speaker. As for to hold, if an object you have with you is too big to grasp by your hands, only ある can be used. Then, as for to possess, the size doesn't matter. If you'd like to emphasize that you own a house, 持っている is better to be used: 私は、家を持っています。 Another example:If you own an expensive ring, （私は）高い指輪を持っています is better to describe you own a ring than 高い指輪があります. (Q)And as you said, that 私はカメラがあります sound unnatural... does it mean that 私はshould better not be user with the あります？ or can it be correct in some other examples? maybe: 私は時間があります。?　 (A)This is difficult to answer. As you speculate, 私は should better not with があります in this case. As for the structure X(人）はYがあります, If Y is a thing like a camera or car, it would sound awkward. In this case, X(人)はYを持っています would fit better. ？私はペンがあります。⇒〇私はペンを持っています。 ？私はカメラがあります。⇒〇私はカメラを持っています。 If Y is not a thing but an abstract property like 才能, it would sound natural. 〇私は才能があります。 〇私は夢があります。 I guess this is natural too. 〇私は時間があります。 I'm not a teacher or a linguist. But I hope this makes sense to you!

私はカメラがあります is little bit weird. Because あります means not "have" but "there is(are)" in English. If this sentence is 私の家にはカメラがあります, it is correct. (This meaning is there is a camera in my house. ) But you want to say "I have a camera", so カメラを持っています is more natural.

Hola, estoy acuerdo con Selly-san. Y escribí una nota sobre "tener" en japonés. Si quieres, echa un vistazo a esa. (https://www.italki.com/notebook//entry/601901) Espero que te ayude.

i think both "もっている" and "ある" are same meaning at this situation