USceneCaptureComponent2D does not capture the same result as BackBuffer

Development Programming & Scripting C++
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1

I have a USceneCaptureComponent2D *SceneCapture capturing the scene.
The result is darker than the BackBuffer.

I tried the following code to keep the PostProcessSettings the same as SceneView->FinalPostProcessSettings, it does not make any difference.

// Called every frame
void AXXXXX::Tick(float DeltaTime)
{
    Super::Tick(DeltaTime);
    APlayerController *OurPlayerController = UGameplayStatics::GetPlayerController(this, 0);
    OurPlayerController->SetViewTarget(OurCamera->GetAttachParentActor());

    APawn* Pawn = OurPlayerController->GetPawn();
    check(Pawn);
    UCameraComponent* MainCamera = Cast<UCameraComponent>(Pawn->FindComponentByClass<UCameraComponent>());
    check(MainCamera);


    ULocalPlayer* LocalPlayer = OurPlayerController->GetLocalPlayer();
    check(LocalPlayer);
    check(LocalPlayer->ViewportClient);
    
    SceneCapture->ShowFlags = LocalPlayer->ViewportClient->EngineShowFlags;

    FSceneViewFamilyContext ViewFamily(FSceneViewFamily::ConstructionValues(
        LocalPlayer->ViewportClient->Viewport, GetWorld()->Scene, LocalPlayer->ViewportClient->EngineShowFlags)
        .SetRealtimeUpdate(true));

    FVector ViewLocation;
    FRotator ViewRotation;
    FSceneView* SceneView = LocalPlayer->CalcSceneView(&ViewFamily, ViewLocation, ViewRotation, LocalPlayer->ViewportClient->Viewport, nullptr, INDEX_NONE);
    check(SceneView);
    
    SceneCapture->PostProcessBlendWeight = 1.0f;
    SceneCapture->PostProcessSettings = SceneView->FinalPostProcessSettings;

    //SceneCapture->PostProcessSettings = MainCamera->PostProcessSettings;
    //SceneCapture->PostProcessSettings.bOverride_AutoExposureMinBrightness = true;
    //SceneCapture->PostProcessSettings.AutoExposureMinBrightness = 2.0f;
}

I tried SceneCapture->PostProcessSettings = MainCamera->PostProcessSettings; too, it does not make difference neither.

But these two lines can make the result more brighter

    SceneCapture->PostProcessSettings.bOverride_AutoExposureMinBrightness = true;
    SceneCapture->PostProcessSettings.AutoExposureMinBrightness = 2.0f;

Question : How to ensure USceneCaptureComponent2D captures the same result as BackBuffer?

Thanks in advance