<p>Alex,</p> <p>By default, ENVI opens 16-bit unsigned integer imagery with an Optimzed Linear stretch. It opens all other data types (excluding 8-bit) with a linear 2% clip stretch. That may explain why you're seeing a difference when opening the UAV ortho products in ENVI. You can disable these default stretches by going to File &gt; Preferences. Click the "Display General" category, then change the Default Stretch for 16-bit Uint and all other imagery to "No Stretch." Let us know if this resolves your issue.</p>

<p>Thanks a lot Jason- problem solved!</p>

<p>Histograms are not representations of the actual data values but rather they are binned values where the bins are automatically calculated in both ENVI and Arc.&nbsp; You can use a variety of binning/stretch types to display the data on a computer screen which is limited to values of 0-255 in&nbsp;each R, G, B.&nbsp; </p> <p>So when you open your image in ENVI, you can go to the drop-down stretch types and select 'Linear' which I think should be the same as ArcGIS Min-Max stretch type.&nbsp; You can also bring up the Custom Stretch tool to view the histograms and how the stretch types affect them.&nbsp; But these stretch types are for display purposes only and how they are binned is to represent the shape/volume of the data values.&nbsp; The actual data values should be the same between ENVI and Arc.&nbsp; If you calculate statistics on your dataset in ENVI and in Arc, they should have the same min/max/mean/SD.&nbsp; In ENVI, when you calculate statistics and scroll to the histogram information, you should also see the 'bin size' for the histogram on the left side of the dialog.&nbsp; I am not sure where to find this equivalent information in Arc but I suspect this might be the difference.</p>

<p>Thanks Mari! Amazing how much I've learned just working with these images. Indeed I realized what you had said when I inspected ascii data from different histogram stretches; there was no difference. Makes sense. Thanks!&nbsp;</p> <p><br /> </p>