diff --git a/docs/lit/examples/2-rotate.jl b/docs/lit/examples/2-rotate.jl
index 218ed23..6d10d75 100644
--- a/docs/lit/examples/2-rotate.jl
+++ b/docs/lit/examples/2-rotate.jl
@@ -81,7 +81,7 @@ jim(image, "Original image")
 # Now plan the rotation
 # by specifying
 # * the image size `nx` (it must be square, so `ny=nx` implicitly)
-# * the `DataType` used for the work arrays.
+# * the `Type` used for the work arrays.
 
 plan2 = plan_rotate(size(image, 1); T)
 
diff --git a/docs/lit/examples/3-psf.jl b/docs/lit/examples/3-psf.jl
index b047056..badcd7b 100644
--- a/docs/lit/examples/3-psf.jl
+++ b/docs/lit/examples/3-psf.jl
@@ -77,7 +77,7 @@ Now plan the PSF modeling
 by specifying
 * the image size (must be square)
 * the PSF size: must be `px × pz × ny × nview`
-* the `DataType` used for the work arrays.
+* the `Type` used for the work arrays.
 =#
 
 plan = plan_psf( ; nx, nz, px, T)
diff --git a/src/fft_convolve.jl b/src/fft_convolve.jl
index 1a60790..7c972eb 100644
--- a/src/fft_convolve.jl
+++ b/src/fft_convolve.jl
@@ -57,7 +57,7 @@ Convolve 2D image `img` with 2D (symmetric!) kernel `ker` using FFT.
 function fft_conv(
     img::AbstractMatrix{I},
     ker::AbstractMatrix{K};
-    T::DataType = promote_type(I, K, Float32),
+    T::Type{<:AbstractFloat} = promote_type(I, K, Float32),
 ) where {I <: Number, K <: Number}
 
     ker ≈ reverse(ker, dims=:) || throw("asymmetric kernel")
@@ -132,7 +132,7 @@ Adjoint of `fft_conv`.
 function fft_conv_adj(
     img::AbstractMatrix{I},
     ker::AbstractMatrix{K};
-    T::DataType = promote_type(I, K, Float32),
+    T::Type{<:AbstractFloat} = promote_type(I, K, Float32),
 ) where {I <: Number, K <: Number}
 
     ker ≈ reverse(ker, dims=:) || throw("asymmetric kernel")
diff --git a/src/plan-psf.jl b/src/plan-psf.jl
index 6b3460f..445dcdf 100644
--- a/src/plan-psf.jl
+++ b/src/plan-psf.jl
@@ -5,7 +5,7 @@ import AbstractFFTs
 import FFTW
 
 """
-    PlanPSF{T,Tf,Ti}( ; nx::Int, nz::Int, px::Int, pz::Int, T::DataType)
+    PlanPSF{T,Tf,Ti}( ; nx::Int, nz::Int, px::Int, pz::Int, T::Type)
 Struct for storing work arrays and factors for 2D convolution for one thread.
 Each PSF is `px × pz`
 - `T` datatype of work arrays (subtype of `AbstractFloat`)
@@ -41,7 +41,7 @@ struct PlanPSF{T, Tf, Ti}
         nz::Int = nx,
         px::Int = 1,
         pz::Int = px,
-        T::DataType = Float32,
+        T::Type{<:AbstractFloat} = Float32,
     )
 
         T <: AbstractFloat || throw("invalid T=$T")
@@ -84,7 +84,7 @@ end
 
 
 """
-    plan_psf( ; nx::Int, nz::Int, px::Int, pz::Int, nthread::Int, T::DataType)
+    plan_psf( ; nx::Int, nz::Int, px::Int, pz::Int, nthread::Int, T::Type)
 Make Vector of structs for storing work arrays and factors
 for 2D convolution with SPECT depth-dependent PSF model,
 threaded across planes parallel to detector.
@@ -102,7 +102,7 @@ function plan_psf( ;
     px::Int = 1,
     pz::Int = px,
     nthread::Int = Threads.nthreads(),
-    T::DataType = Float32,
+    T::Type{<:AbstractFloat} = Float32,
 )
     return [PlanPSF( ; nx, nz, px, pz, T) for id in 1:nthread]
 end
diff --git a/src/plan-rotate.jl b/src/plan-rotate.jl
index f791858..bcb91ad 100644
--- a/src/plan-rotate.jl
+++ b/src/plan-rotate.jl
@@ -46,7 +46,7 @@ struct PlanRotate{T, R}
 
     function PlanRotate(
         nx::Int ;
-        T::DataType = Float32,
+        T::Type{<:AbstractFloat} = Float32,
         method::Symbol = :two, # :one is for 1d interpolation, :two is for 2d interpolation
     )
 
@@ -78,7 +78,7 @@ end
 
 
 """
-    plan_rotate(nx::Int; T::DataType, method::Symbol)
+    plan_rotate(nx::Int; T::Type{<:AbstractFloat}, method::Symbol)
 Make `Vector` of `PlanRotate` structs
 for storing work arrays and factors
 for threaded rotation of a stack of 2D square images.
@@ -95,7 +95,7 @@ for threaded rotation of a stack of 2D square images.
 """
 function plan_rotate(
     nx::Int ;
-    T::DataType = Float32,
+    T::Type{<:AbstractFloat} = Float32,
     method::Symbol = :two,
     nthread::Int = Threads.nthreads(),
 )
diff --git a/src/psf-gauss.jl b/src/psf-gauss.jl
index 0dbff28..9d38163 100644
--- a/src/psf-gauss.jl
+++ b/src/psf-gauss.jl
@@ -17,7 +17,7 @@ having specified full-width half-maximum (FHWM) values.
 - 'fwhm::AbstractVector{<:Real} = range(fwhm_start, fwhm_end, ny)'
 - 'fwhm_x::AbstractVector{<:Real} = fwhm,
 - 'fwhm_z::AbstractVector{<:Real} = fwhm_x'
-- 'T::DataType == Float32'
+- 'T::Type == Float32'
 
 Returned `psf` is `[px, pz, ny]` where each PSF sums to 1.
 """
@@ -30,7 +30,7 @@ function psf_gauss( ;
     fwhm::AbstractVector{<:Real} = range(fwhm_start, fwhm_end, ny),
     fwhm_x::AbstractVector{<:Real} = fwhm,
     fwhm_z::AbstractVector{<:Real} = fwhm_x,
-    T::DataType = Float32,
+    T::Type{<:AbstractFloat} = Float32,
 )
     isodd(px) || @warn("even px = $px ?")
     isodd(pz) || @warn("even pz = $pz ?")
diff --git a/src/rotatez.jl b/src/rotatez.jl
index 5abd9dc..8ff5495 100644
--- a/src/rotatez.jl
+++ b/src/rotatez.jl
@@ -371,7 +371,7 @@ function imrotate(
     img::AbstractMatrix{I},
     θ::RealU;
     method::Symbol=:two,
-    T::DataType = promote_type(I, Float32),
+    T::Type{<:AbstractFloat} = promote_type(I, Float32),
 ) where {I <: Number}
     output = similar(Matrix{T}, size(img))
     plan = plan_rotate(size(img, 1); T, nthread = 1, method)[1]
@@ -424,7 +424,7 @@ function imrotate_adj(
     img::AbstractMatrix{I},
     θ::RealU;
     method::Symbol=:two,
-    T::DataType = promote_type(I, Float32),
+    T::Type{<:AbstractFloat} = promote_type(I, Float32),
 ) where {I <: Number}
     output = similar(Matrix{T}, size(img))
     plan = plan_rotate(size(img, 1); T, nthread = 1, method)[1]
diff --git a/src/spectplan.jl b/src/spectplan.jl
index 6905626..e0955ff 100644
--- a/src/spectplan.jl
+++ b/src/spectplan.jl
@@ -30,7 +30,7 @@ Currently code assumes the following:
 * multiprocessing using # of threads specified by `Threads.nthreads()`
 """
 struct SPECTplan{T}
-    T::DataType # default type for work arrays etc.
+    T::Type{<:AbstractFloat} # default type for work arrays etc.
     imgsize::NTuple{3, Int}
     px::Int
     pz::Int
@@ -56,7 +56,7 @@ struct SPECTplan{T}
         mumap::Array{<:RealU, 3},
         psfs::Array{<:RealU, 4},
         dy::RealU;
-        T::DataType = promote_type(eltype(mumap), Float32),
+        T::Type{<:AbstractFloat} = promote_type(eltype(mumap), Float32),
         viewangle::StepRangeLen{<:RealU} = (0:size(psfs, 4) - 1) / size(psfs, 4) * T(2π), # set of view angles
         interpmeth::Symbol = :two, # :one is for 1d interpolation, :two is for 2d interpolation
         nthread::Int = Threads.nthreads(),