So I’m going to Europe in about a month and am wondering whether it’d be a mistake to rely on my iPhone as my only camera. Has anyone ever done this?
This is a question I've been mulling for several years now. The easy generic answer is to take both, then use one or both of them as you see fit on your trip. Just be sure to get in at least several days (preferable weeks) of practice with any new apps or gear before your trip.
But if you want an answer more tailored to you, there are a lot of competing factors to consider.
• what kinds of photos do you want to take?
Mostly documenting your trip or photography as digital art?
• what will you do with your photos after?
Share them on social media or use display them on high res screens?
• how much trouble will it be to bring your DSLR?
Are you spending most of your time in one or two cities (and can leave the camera bag at the hotel some days), or are you doing a whirlwind tour of the continent and will have to lug the camera bag everywhere?
• do you enjoy post processing in Lightroom and Photoshop?
The iPhone takes great snapshots, panoramas, and time lapse photography. 4/5 times it does it automatically without the need for much if any post processing. It's light and always at hand. And the iPhone makes it exceptionally easy to share photos with friends and family, directly through the Photos app, texts, or via social media. It also geotags the location of all of your photos (many DSLRs do not) so you'll always know where you took the photo. And Apple also plots them on a map!
In most cases, iPhones take better photos strait out of the camera -- which is usually what you want 9/10 times. DSRL RAW images typically require post processing, which is an added hassle for 9 of 10 images. But it can produce superior results for that 1 in 10.
**If** you enjoy post processing images in Lightroom and Photoshop to take your best images and dial them up to 11, in order to use them as high resolution wallpaper or make prints, then a DSLR is the better choice.
• The image quality from a large DLSR lens will usually beat that from a tiny iPhone lens.
• A DSLR will do better in low light in most situations
• A DSLR is usually better when high shutter speed is required (sports, taking photos from a boat, train, car)
• And a DLSR shooting in RAW will provide more usable color and exposure information (especially if you bracket your shots).
But most of the DSLR advantages require editing *and* viewing on a large screen. If your pictures are mainly going to be seen on other phones or on Facebook, then the differences in image quality won't be that apparent. And people won't be looking at them for more than a few seconds. And almost no one but you will be looking at them after a year or two.
About 80% of the photos I take on vacations could be left to the iPhone. The other 20% will be better with a DSLR, about 5% of which can be radically transformed from okay to wow via post processing in RAW.
Here are some examples -- not necessarily my best, but quick illustrations of how Lightroom/Photoshop can sometimes transform flat images in ways that would be hard to achieve if taken from an iPhone.
First images are SOOC (Straight Out Of the Camera) without editing, and closer to iPhone defaults. The second images are the post processing results that require a lot of manipulation of RAW data. [Note too that these images lose a lot of resolution here too, which diminishes the benefit of a DSLR]