Because the Nikon D40 is a compact DSLR camera, the compartment for the battery and card slot for the memory card are as compact as possible. It is only logical that pictures made by the Nikon D40 are saved on a Secure Digital card. The Nikon D40 is also SDHC compatible, so that you can also use cards larger than 2GB. This is one of Secure Digital's advantages; they are available in large capacities, in different speeds and are sold almost everywhere. This small flash card's compatibility with other devices is also large and wide spread. Not unimportantly, it's relatively inexpensive and most compact cameras use SD as a storage medium. If you are making the transition from a compact camera to a Nikon D40, you can continue to use your memory cards. Only users who want to use a D40 in addition to a D70s or D200 will need to carry two different cards around, but somehow I don't think that this will be a very large group.
Nikon D40 digital SLR camera - Image formats
Photos can be saved in JPEG or the raw NEF format. NEF and JPEG at the same time is also possible, but then you always have JPEG in the basic compression. It is a pity that you can't choose to save a JPEG fine or normal with the NEF. To transform NEF files into TIFF or JPEG you must use the Picture Project that comes with the camera. Other software, such as Adobe Camera RAW, can not yet deal with the D40. That will change with the next Adobe update, which is good, because I'm not a great fan of PictureProject. It is too simple, you can't regulate much yourself and it's too slow. I would definitely invest in a new version of Nikon Capture or Adobe Camera RAW as soon as they are suitable for the D40 NEF format. I prefer to photograph in NEF because you can then adjust the white balance without any problems and you have more room to manoeuvre in the exposure. Fortunately, JPEGs from the Nikon D40 are also excellent. The large format Fine JPEGs are excellent quality and the difference to NEF is barely perceptible. However, you then miss the extended correction options. At higher compressions, especially in Basic, you can see jagged edges, something that is not really unusual. I would advise anyone using JPEG to only work in the very highest quality.
Nikon D40 DSLR camera - Large buffer
The Nikon D40 has a very large buffer. With 100 JPEGs in the very highest quality or 5 NEF pictures, it gives you enough to be going on with. The photos are recorded quickly to the Secure Digital memory card. The standard memory cards also work very quickly. If you take a lot of action photos, a quick memory card like the SanDisk Extreme III is certainly worth while. With a full buffer, you can keep taking photos at 1.5-2 pictures per second. Using smaller cards reduces the speed to 1 picture per second. If you usually photograph still standing subjects, you will be fine with a standard card prima. Make sure you have a memory card with enough capacity. Even if you 'only' work with 6 Megapixels, the files soon take up a lot of space. A 1GB card, as shown in the following table, is not a superfluous luxury.
Nikon D40 SLR - 1000mAh EN-EL9 Lithium Ion battery
Nikon has developed a new battery for the energy supply. The Nikon D40 digital SLR uses a 1000mAh EN-EL9 Lithium Ion battery. It is a pity that it doesn't use an existing battery, but they were probably too large. This is annoying if you use the Nikon D40 in addition to a D80 or if you switch from a D40 to a D80, as you will need two different chargers. I'm in favour of standardising things as much as possible. Everyone benefits from this. Costs can drop, profit margins rise and users need less things. The Nikon D40 is economical with power, even though it uses the LCD display a lot. It is possible to take several hundred pictures. It's still handy however, to buy a second battery, so you will never be without power. After all, who cannot say that they've never been on the point of taking a unique picture, only to discover that their battery is flat?