As both models are part of Lexar’s professional series, both are identical in size and shape. In fact, both are nearly interchangeable for the 3400X series they replace. That is to say all are elegant, classy; however yet unlike the 1066 vs 3400x series, these two new models cannot be easily confused with one another. This is because Lexar has opted for their ‘silver’ motif for the 3500X and their ‘gold’ for their 3600X. As we will see later in the review, this silver vs gold impression has more to do with asking price than performance – as both have stellar performance!Also on the positive side the back of the case not only goes over the usual details but also states what the card’s performance rating is in MB/s. More importantly it lists both the read and write performance specifications. In the 3500X case that is 445MB/s write, and 510MB/s read write; whereas the 3600X’s case it is 445MB/s and 540MB/s. Compare and contrast that with the 3400X’s 270/510 specifications and both of these new models are obvious improvements over their predecessor in the crucial write department.
Continuing the silver and gold trend the 3500X CFast 2 card itself uses a silver color scheme, whereas the 3600X uses the more classical gold. This is actually a good thing as telling one from the other is as simple as looking at them. We personally have lost count of the number of times we have reached into our parts bag and pulled out a 3400X CFast card (and tried using it) when a CF card was needed…and vice versa.The only possible confusion will be between the 3600X and the 1066x/800x/ etc CF card series. This is because the gold color scheme was always used for professional grade CF cards, and now with the CFast card also using it…things can get tricky. Luckily, most still photography enthusiasts will be upgrading from 800/1066 cards (and cameras) to the 3500X, and here the silver does stick out nicely. Also, Lexar has upgrade the gold design so it is not that difficult to tell the new from the old.
Beyond the label there is also a few other minor points of variance. While yes both use the CompactFlash/CFAST type 1 form-factor of 43mm X 36mm X 3.3mm the 3600X does weight slightly more than the 3500X. To be precise the 3500X weighs in at 8.5grams (or about the same as the 3400X series), whereas the 3600X is 11grams. This may not sound like much, but is actually a 29 percent difference. While some of this difference is due to the increased amount of NAND used in the 128GB models vs 64GB capacity models, a lot of it has to do with the extra beefy heatsink used on the 3600X.
Basically the 3500X makes use of the same heatsink design as the 3400X (that is to say very capable for a still photography card), but the 3600X uses more metal. This is because the 3600X is expected to be in continues use until full, whereas the 3500 and 3400 series are more intended for burst shooting and then followed by short periods of cool down. This increased cooling is one of the ways in which the 3600X can guarantee better continuous performance.
The other way in which these two series differ is in the firmware. As we will show you in the testing stage the 3600X’s firmware has been tweaked for increase sequential and large file handling performance. This makes sense as 4K ARRI cameras deal with massive files and only massive files so making this area paramount does make sense. However, the downside to this is the 3500X can actually be faster than the 3600X in certain circumstances – as it is expected to be dealing with a wide variety of file sizes in a more random pattern.
Sadly, due to the lack of camera’s using CFast 2, there is also a lack of governing standards. This is why the seemingly faster 3600X can sometimes be outclassed by the 3500X – as the ‘4K’ standard is rather lax compared to VPG standards previous CF cards were held to. Hopefully as cameras come out that use CFast 2.0 this lack of standards will be rectified and allow consumers a better idea on what to expect from each model!
On the positive side, internally both are very similar in their layout and design with both using 4 NAND ICs, a ram IC for cache, and a high performance SATA controller.