# Thumbnail image information on the NextSeq 500/550

On the NextSeq 500/550, thumbnail images are disabled by default to prevent Real Time Analysis (RTA) from running slowly. \* Enabling thumbnail images can aid in troubleshooting.

**Thumbnail images location: and nomenclature**

* File Path: D:\Illumina\ NextSeq Control Software Temp\\
* Temp\[Run\_Folder]\Thumbnail\_Images\L00\[4]\C\[25.1] (Lane 4, Cycle 25, tiles 01)

**Thumbnail images nomenclature:**\* \[Run\_Folder]\Thumbnail\_Images\L00\[X]\C\[Y.1] ]

* X refers to the lane number
* Y refers to the cycle number.
* Saves thumbnail images only for tiles 01, 06, and 12.
* **Flow cell**
* 4 Lanes
* 2 Surfaces (1 = top, 2 = bottom)
* **Swaths**
* Mid Output flow cell = 1 swath
* High Output flow cell = 3 swaths
* 6 sections (six cameras)
* **Tiles represented in two digits**
* Mid Output flow cell: 144 tiles (4 lanes x 1 swath x 3 sections x 12 tiles)
* High Output flow cell: 432 tiles (4 lanes x 3 swaths x 3 sections x 12 tiles)
* Both flow cell tiles are numbered 01--12
* **Thumbnail file naming format**: s\_\[lane]\_\[tile numbering]\_\[channel].jpg
* **Tile numbering format**: \[Surface]\[Swath]\[Section]\[Tile]
  * Example:\
    \- s\_2\_21206\_green.jpg\
    \* lane 2\
    \* bottom surface\
    \* swath 1\
    \* section 2\
    \* tile 06\
    \* green channel

**References:**

* [Two-Channel SBS Technology](https://www.illumina.com/science/technology/next-generation-sequencing/sequencing-technology/2-channel-sbs.html)
* [NextSeq 500/500 Sequencing Systems Product Documentation](https://support-docs.illumina.com/IN/NextSeq_550-500/Content/IN/FrontPages/NextSeq-550-500.htm) (section **Flow Cell Tiles** in Sequencing Output files)
* For further information, see for Knowledge Base article [How to turn on thumbnails for troubleshooting on the NextSeq 500/550](https://knowledge.illumina.com/instrumentation/nextseq-500-550/instrumentation-nextseq-500-550-reference_material-list/000002085).

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