"This appears to be photograph of wounded solders in a hospital. I am going to go ahead and call it as being by Mathew Brady."
This usage is spoken: "I'm going to go ahead and call it as being x".
To call something is sports' lingo for what a referee does during a game: to call a foul or to call a play. For example. It has come to mean: to say something about something, to define it.
When looking at a picture or listening to something wherethe person who took the picture or recorded the music or speech, respectively, is not clear, it would be standard AmE spoken English to say: I'm going to call it as being by [some photographer or painter or musician].
This would be used for anything where identifying a person is the issue.
Also, very used: I'm going to call it as I see it. You did steal the money. [Let's say you are having an argument, and you say you did not do something bad. The other person can say that sentence to you.]
Who took the picture? Who is the photography by? Who is the man in the photo? Who is the person recording the message or music?
"I'm going to call it as being John [who took the picture OR made the recording OR who is in the picture].
In this type of case, as being is necessary.
- I'm going to go ahead and call it as being x"
Go ahead implies there has been hesitation until that point in time.
"As being x" is in line with : x is identified as being [some person or thing].