Film Characteristics
The "flavor" differences between films from different manufacturers are essentially reflected in measurable parameters determined by chemical formulas and crystal structures. Below are real parameters from authoritative technical data sheets.
1. KODAK TRI-X 400 (Classic News Film)
Source: Kodak Official Technical Data Sheet F-4017
| Parameter | Value | Description |
|---|---|---|
| Sensitivity | ISO 400/27° | Base exposure index |
| RMS Granularity | 17 (D-96 dev, 6 min) | Higher value means more visible grain |
| Gamma (Contrast) | 0.70 (Standard dev) | Medium contrast, good shadow detail retention |
| Dmax | 2.2-2.4 | Maximum black density |
| Dmin | 0.10-0.12 | Base + fog density |
| Spectral Sensitivity | Panchromatic, peak ~550nm | Response extends to ~690nm |
| Resolution | 100 lp/mm (1000:1 contrast) | Resolving power at high contrast |
| Reciprocity Failure | +1 stop compensation at 1s | Long exposure characteristic |
Flavor Characteristics: Wide exposure latitude (±2 stops still usable), rugged "breathing" grain, good shadow detail retention.
2. FUJIFILM Velvia 50 (Landscape Slide Film)
Source: Fujifilm Technical Data Sheet
| Parameter | Value | Description |
|---|---|---|
| Sensitivity | ISO 50/18° | Daylight base |
| Gamma | 1.2-1.4 (E-6 process) | Extremely high contrast, saturated colors |
| Dmax | 3.5-4.0 | Higher maximum density for slide film |
| Dmin | 0.15-0.20 | Transparent base density |
| Granularity | RMS 9 (Granularity Index) | Extremely fine grain |
| Spectral Sensitivity | Peak R=650nm, G=550nm, B=450nm | Strong red layer response, darkened blue sky |
| Resolution | 160 lp/mm | Ultra-high resolution, sharp details |
| Reciprocity Failure | +1/3 stop above 1/4000s | Short exposure characteristic |
Flavor Characteristics: High color saturation (especially red, orange), strong contrast, deeper blue sky rendering, fine grain but narrow exposure latitude (±0.5 stops).
3. ILFORD HP5 Plus (General Purpose B&W)
Source: ILFORD Official Data Sheet
| Parameter | Value | Description |
|---|---|---|
| Sensitivity | ISO 400/27° | Base value, pushable to EI 3200 |
| RMS Granularity | 16 (D-96 dev) | Close to Tri-X, traditional cubic crystals |
| Gamma | 0.65-0.75 | Low-medium contrast, suitable for scanning |
| Dmax | 2.1-2.3 | Maximum density |
| Dmin | 0.08-0.10 | High base transparency |
| Spectral Sensitivity | Panchromatic, tested at 2850K Tungsten | Red response slightly lower than Tri-X |
| Resolution | 95 lp/mm | Slightly lower than Tri-X |
| Push Characteristics | Gamma rises to 0.9 at EI 1600 | Significant contrast increase when pushed |
Flavor Characteristics: Excellent push performance (usable at EI 3200), soft grain structure, smooth highlight roll-off, rich shadow gradations.
4. Mathematical Expression of Parameter Differences
These parameters directly determine the shape of the H-D Curve:
$$ D(E) = D_{\text{min}} + \frac{D_{\text{max}}-D_{\text{min}}}{1 + 10^{\gamma(\log E_0 - \log E)}} $$
- Tri-X: Lower $E_0$, long toe, large latitude
- Velvia: Extremely high $D_{\text{max}}$, large $\gamma$, steep shoulder
- HP5: Lower $D_{\text{min}}$, $E_0$ shifts right when pushed
Spectral Sensitivity Differences: $$ S(\lambda){\text{Velvia}} > S(\lambda){\text{Tri-X}} > S(\lambda)_{\text{HP5}} \quad (\lambda > 600\text{nm}) $$
5. Authoritative Verification Suggestions
- Official Data Sheets: Kodak Alaris (kodakprofessional.com), Fujifilm, ILFORD (ilfordphoto.com)
- Third-party Testing: Imatest software MTF analysis, X-Rite densitometer measurement of Dmax/Dmin
- Measurement Methods: Verify Gamma using Stouffer step wedge + standard development process
These parameters are direct quantifications of film chemical formulas and crystal technologies, which are more reliable than subjective "flavor" descriptions.