Hello, I am a male. Is having a magazine that contains no pornographic or sexually explicit photos (something that I actually oppose) wrong when they contain photographs of adult girls who are dressed in lingerie or swim-suits or are not fully dressed, i.e. no bra on or no underwear on, or fully naked even if it is not a full frontal picture of them? Is is still fornication or sexual immorality? Even if it is, as I said, not pornographic or sexually explicit at all?
The reason pornography is a sin is because it involves lust. Lust is desiring something that sinful so strongly that you are justifying the sin in your mind. "But I say to you that whoever looks at a woman to lust for her has already committed adultery with her in his heart" (Matthew 5:28). Lusting for something sinful is just as wrong as actually committing the sin itself.
Anything used to stir sexual desire for women you are not married to would be a form of lust. "For this is the will of God, your sanctification: that you should abstain from sexual immorality; that each of you should know how to possess his own vessel in sanctification and honor, not in passion of lust, like the Gentiles who do not know God" (I Thessalonians 4:3-5). "Passion of lust" refers to lustful things used to stir up lust in other people. This would include pictures of partially or fully nude people or scantily clad people, especially those found in men's magazines.