The ApeCase ACPro1720W is a very unusual backpack that just might be the coolest backpack ever. It is called a "Converta-Pack" as there are really two camera bags in one. There is a small camera bag, that I like to call an excursion or day bag that can hold a DSLR with a lens attached. It can be used independantly, or it can be attached to the main backpack.
This is a very useful feature for travel photography as you can take all of your gear to your hotel or stateroom, off-load the heavy stuff, then take just what you need for the afternoon. This is in some ways a "mother ship" approach that I very much like.
When the smaller excursion bag is detached from the backpack, it can be used by itself like a sling or shoulder bag, but it can also be attached to the front of the backpack - on the shoulder harness - for a chest pack.
There are some very nice features on the backpack. One I really like is the ability to adjust the harness to your height. This is very unusual for a photo backpack, and since I am a tall person, I really appreciate the ability to height-adjust the backpack.
I can adjust this bag so that the waist straps ride properly rather than being too high like many bags do. And the belt must be a good 60" long, so it will fit virtually anyone.
The sternum strap is also adjustable - which again - for a tall person, keeps from choking you as on many backpacks, the strap is right at your neck level.
One unusual feature is the flashlight holder built into the left harness strap. It will hold an AA powered flashlight such as this mini-Mag light.
There are detents in the holder so you can rotate it to the correct position needed.
Other unusual featuers include an expandable bottom, which can be used for a jacket - your lunch - or other items. I would not put anything fragile into this area however, as it is not padded.
Like most photo bags, there are several adjustable padded dividers in the main compartment. The main bag is deep as well - deep enough for a 70-300mm lens. Plus the bright yellow interior helps you find items in low-light conditions.
A full sized 70-200mm f/2.8 zoom will even fit if you insert it from the top zippered opening of the bag. One word of caution though - you can easily put 25 to 30lbs of gear in this bag, so you will have to remember that when you start filling it up. At least with a backpack style bag - and if you use the excursion bag as a chest pack, you can distribute the weight better - so the backpack "carries" better than most.
The backpack also includes a nice rain cover. I have also discovered that the rain cover has a reflective side, which you could likely use for an emergency reflector if you use it with the reflective side out.
While the rain cover is not detachable, when it covers the backpack, it results in a nice sized reflector should you desire to use it as such.
There are two nice tripod holders that especially work well with the Benro Travel Flat tripods; but they will hold almost any other tripod.
It should be remembered that this backpack is in reality a "system", and the smaller "day-bag" can be used independantly for the day's needs. The excursion case can handle up to a full size DSLR, but not with a battery grip - or a pro sized DSLR. In addition to the DSLR, the case can also hold a flash or small second lens.
If you need more room, both the excursion case and the backpack have attachment points that can be used to hold small cases. Many camera bag manufacturers, including Ape Case, Lowe Pro, Tamrac, and others manufacture cases having a hook-and-loop method of attachment. So if you have the need for carrying another lens or item when you go out for the day, you can easily attached such a pouch.
The entire backpack is very comfortable to wear, has plenty of padding, and can be worn for hours without strain. This is usually only possible with backpack style bags, as the shoulder type bags tend to hurt your neck and shoulder after only a short time of use. Backpacks are not liked by many as they make it hard to get to your gear.
However, by attaching the DSLR excursion bag to the front chest area, you have the best of both worlds.