# OD sensitivity seems higher at ODs 2-4 vs ODs \<1 on min-eVOLVER **URL:** \ **Category:** min-eVOLVER Hardware\ **Created:** [April 4, 2025, 2:52pm UTC](https://www.evolver.bio/t/od-sensitivity-seems-higher-at-ods-2-4-vs-ods-1-on-min-evolver/568 "2025-04-04T14:52:18Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![Nate\_Borders](https://yyz1.discourse-cdn.com/flex035/user_avatar/www.evolver.bio/nate_borders/32/268_2.png) [@Nate\_Borders](https://www.evolver.bio/u/Nate_Borders)\ **Post date:** [April 4, 2025, 2:52pm UTC](https://www.evolver.bio/t/od-sensitivity-seems-higher-at-ods-2-4-vs-ods-1-on-min-evolver/568/1 "2025-04-04T14:52:19Z")
I’m quoting an emailed question by @kumarsumanth.m for the forum: > The OD calibration curve shows high sensitivity at OD of 2 to 4 which is quite high for our applications, ideally we work under OD 1. I was wondering if you regulate the LED intensity based on the working OD range. > > ![thumbnail_image](https://canada1.discourse-cdn.com/flex035/uploads/evolver/original/1X/3005b08b2c682db24b98c7ff3a0365708dd723a6.png) > Here are the fit values: > a : 35,286.23 > b : 63,962.66 > c : 2.822 > d : –0.383 ---
**Author:** ![Nate\_Borders](https://yyz1.discourse-cdn.com/flex035/user_avatar/www.evolver.bio/nate_borders/32/268_2.png) [@Nate\_Borders](https://www.evolver.bio/u/Nate_Borders)\ **Post date:** [April 4, 2025, 2:57pm UTC](https://www.evolver.bio/t/od-sensitivity-seems-higher-at-ods-2-4-vs-ods-1-on-min-evolver/568/2 "2025-04-04T14:57:41Z")
Responding to the question: Sumanth is talking about the rate of change of ADC values as a function of OD, which should not matter too much after calibration. As you see, the min-eVOLVER should be able to distinguish between values up to OD ~5, when in OD 90 mode. It will simply get more noisy at higher ODs. However, it should actually be best in the 0.2 - 1.5 range due to less noise. ### OD 135: Depending on how accurate you want your ODs to be in the 0 - 0.2 range, you may want to switch it to OD 135 mode. Before doing so, double check that OD 90 won’t work for you by doing a calibration in the OD range that you want and excluding higher OD standards. See [here](https://khalil-lab.gitbook.io/evolver/extensions/min-evolver/min-evolver-construction/construction-protocol#od-90-vs-od-135) if you want to switch to OD 135 and check the figure above for how to make the swap. I’m not 100% sure you have photodiodes in the OD 135 positions, so double check that as well. Fair warning, OD 135 is currently less characterized than OD 90 in the min-eVOLVER. ---
**Author:** ![kumarsumanth.m](https://avatars.discourse-cdn.com/v4/letter/k/977dab/32.png) [@kumarsumanth.m](https://www.evolver.bio/u/kumarsumanth.m)\ **Post date:** [April 4, 2025, 6:35pm UTC](https://www.evolver.bio/t/od-sensitivity-seems-higher-at-ods-2-4-vs-ods-1-on-min-evolver/568/3 "2025-04-04T18:35:05Z")
Thank you, Nate. My working OD range is between 0 to 1. Are you saying that OD90 which generated the current calibration curve is good enough for it? otherwise I’ll try OD135. ---
**Author:** ![Nate\_Borders](https://yyz1.discourse-cdn.com/flex035/user_avatar/www.evolver.bio/nate_borders/32/268_2.png) [@Nate\_Borders](https://www.evolver.bio/u/Nate_Borders)\ **Post date:** [April 4, 2025, 7:34pm UTC](https://www.evolver.bio/t/od-sensitivity-seems-higher-at-ods-2-4-vs-ods-1-on-min-evolver/568/4 "2025-04-04T19:34:06Z")
Yeah try OD90 with standards from 0 to 1. ---
**Author:** ![kumarsumanth.m](https://avatars.discourse-cdn.com/v4/letter/k/977dab/32.png) [@kumarsumanth.m](https://www.evolver.bio/u/kumarsumanth.m)\ **Post date:** [April 4, 2025, 8:33pm UTC](https://www.evolver.bio/t/od-sensitivity-seems-higher-at-ods-2-4-vs-ods-1-on-min-evolver/568/5 "2025-04-04T20:33:51Z")
Sure, I’ll try that.