Is overexposing 1 stop normal?

Bikerider · Jan 2, 2020

Sirius Glass said:
I have used Portra 400 for many years, while it has a wide exposure latitude, stick to box speed until you have a good reason to vary from there stick to box speed.

Exactly!

A question for your good self. I have never used a 400 speed colour film, how different is the grain when compared to 200. For instance with 200 enlarged to 12 x 16, the grain is very muted and insignificant, is a 400 film likely to be similar? The extra speed would be very useful especially with the lower light level in winter.

138S · Jan 2, 2020

Until 1960 overexposing 1 stop it was normal, ASA (now ISO) was changed by 1 stop. That stop was considered a safety factor and in 1960 all films were rated the double in the box without changes in the manufacturing, they supressed that safety factor as the general rule it was until then.

If using calibrated ISO speed then we always have 3.3 stops latitude in the shadows, at -3.3 stops we always have 0.1D density over base+fog: Those spots that metered with the spot meter have a -3.3 reading have that density in the negative.

A 1 stop overexposure works like a safety factor for shutter, aperture, meter and photographer inaccuracies. It also overcomes film aging and processing inaccuracies. If we have deep shadows that we want to record then that safety factor is good, if we don't have those deep shadows then that safety factor is way less necessary.

Anyway we may want to meter very accurately to place in the toe some shadows (if the film has long/mid toe), working the tonality of shadows by exposing accurately. This allows a tonal compression that if not done in the taking then later would be difficult to work in an optical print, while it's easy to work in hybrid. A master using film toe was Yousuf Karsh.

Another approach is taking a linear capture that is more flexible and later working the tonal curve in the printing, which may require a substantial effort. No way is better or worse, it's about mastering our tools.

bernard_L · Jan 2, 2020

138S said:
If using calibrated ISO speed then we always have 3.3 stops latitude in the shadows, at -3.3 stops we always have 0.1D density over base+fog:

Can you please indicate where does that 3.3 number come from? As far as I know from a source in print(§)

B+F+0.1 is Zone I
A uniform subject (does not matter what % reflection) metered with a reflected light meter lands on Zone V
(V-I)=4, not 3.3

(§) My reference: Controls in B&W photography, by R.J.Henry. pp 96-97. In the series of articles by Phil Davis, the part on the determination of speed is confused to say the least. And the upper point of the "ASA triangle" is not zone V, just a conventional upper point in the determination of contrast, which is a pre-requisite to the determination of speed.

138S · Jan 2, 2020

bernard_L said:
Can you please indicate where does that 3.3 number come from? As far as I know from a source in print(§)

B+F+0.1 is Zone I

A uniform subject (does not matter what % reflection) metered with a reflected light meter lands on Zone V

(V-I)=4, not 3.3

(§) My reference: Controls in B&W photography, by R.J.Henry. pp 96-97. In the series of articles by Phil Davis, the part on the determination of speed is confused to say the least. And the upper point of the "ASA triangle" is not zone V, just a conventional upper point in the determination of contrast, which is a pre-requisite to the determination of speed.

This is defined in ISO 6:1993 and ISO 2240:2003 norms that are presently in force.

With today's rules you may use any developer for the calibration, developer has to be mentioned in the calibration, some manufacturers like Foma and Bergger use speed increasing developers (Microphen, Berspeed) to hormonate a "fake" rating, Ilford/Fuji/Kodak use instead a Full Speed developer (D-76 reference) for the calibration.

For the ISO speed calibration you have to develop to have a 0.62 C.I. , then you take the exposure that delivers 0.1D over base+fog, that exposure is Speed Point. Meter exposure at calibrated ISO is x10 the light in the speed point, 2 powered to 3.33 (3+1/3, in fact) is exactly 10, (2^ 3 1/3)

In short x10 more light is 3.33 stops. So meter point is x10 more light than in the Speed Point, which is those 3.33 stops.

A source of some inaccuracy is normative for light metters, which is not tight, so light meters may deliver 1/6 of stop variation depending on brand, but usually not more.

Before 1960 meter point was x20 the light in the Speed Point, instead x10, so before 1960 there were 4.3 stops from meter point to Speed Point. That change generated an amazing source of confusion that still remains 60 years later.

That 4.3 stops (x20) is still used today to determine 0.62 gradient development, pre 1960 it was also the meter point, but when ASA/ISO was doubled in 1960 a coefficient was changed in the ISO number calculation and meter point moved to left by 1 stop from 4.3 to 3.3 distance to Speed Point. Present coefficient is 0.8, pre 1960 it was 0.4:

(https://en.wikipedia.org/wiki/Film_speed)

The ISO triangle determines gradient, pre 1960 it also determined meter point, today meter point is one stop at left.

_______________________________

Source of the confusion is that 1960 change, LF photographers that were metering accurately yet continued doing the same like if ISO did not change, but popular photography started to underexpose 1 stop compared to 1959.

... but for sure today from ISO speed to Speed Point you have 3.3.

What some ZS practitioners do ? They say that a 400 film is 200, so they are back to 1959 !!!

bernard_L · Jan 2, 2020

Thank you.
Unfortunately, the ISO norm is not open access, 38 Swiss francs. And the Wikipedia article (and similar on-ine documents) illustrates only the contrast triangle; and this (Wikipedia)

does not tell me where the metered surface falls on the curve.

138S · Jan 2, 2020

bernard_L said:
Unfortunately, the ISO norm is not open access,

No problem, this says the same:

https://www.kodak.com/uploadedfiles...en_motion_education_sensitometry_workbook.pdf

Also this is interesting: https://en.wikipedia.org/wiki/Light_meter

Sorry for that long answer, but as there is an amazing source of confusion about that I thought it was worth to elaborate a reasoning.

bernard_L · Jan 2, 2020

Thank you again. I have this document but did not bother to read through all the steps of the "workbook"!!

138S · Jan 2, 2020

bernard_L said:
Thank you again. I have this document but did not bother to read through all the steps of the "workbook"!!

bernard_L said:
does not tell me where the metered surface falls on the curve.

Let me add that in fact ISO (ASA) rating does not tell were the meter point is, it only says a number calculated from Speed Point exposure, what says where the meter point is are the meter coefficients, pre 1960 meters aimed 4.3 stops over speed point but post 1960 they aimed +3.3, as said, that shift came not because of a change in the meters but from a change in the ASA number calculation.

dmr · Jan 2, 2020

138S said:
No problem, this says the same:

Thanks.

138S · Jan 2, 2020

dmr said:
Thanks.

Not at all, my pleasure

Anyway we should be grateful to kodak for the excellent technical literature they usually released, if they could lower film price by a 30% this would be a perfect world

Ces1um · Jan 2, 2020

dylan77 said:
I have recently moved into shooting film, Currently shooting with Portra 400. Nikon f100

From what I’ve seen on YouTube it seems like overexposing 1, sometimes up to 2 stops is better for a more accurate exposure, than finding the balance (middle of meter), which often leads to under exposure.

Do you guys agree with this?

Thanks

So I've watched a lot of those videos on youtube and I've seen their recommendation for overexposing portra by one stop. Their rationale was that it renders an image in a more soft/pastel colour. They were going for a specific effect. It wasn't done because portra as a rule needs to be overexposed. I would trust your meter but more importantly you need to know the rules when your meter isn't giving you an accurate reading (like when shooting snowy scenes or at the beach or if your subject is backlit).

138S · Jan 2, 2020

Ces1um said:
So I've watched a lot of those videos on youtube and I've seen their recommendation for overexposing portra by one stop. Their rationale was that it renders an image in a more soft/pastel colour. They were going for a specific effect. It wasn't done because portra as a rule needs to be overexposed. I would trust your meter but more importantly you need to know the rules when your meter isn't giving you an accurate reading (like when shooting snowy scenes or at the beach or if your subject is backlit).

+3 stops is also fine with portra and fuji NS / H

José Villa usually rates Pro 400H at EI 200, but then he meters for the shadows, totalling +2 or +3 or +4. If scanning, no problem.

A better recommendation is: take a roll and make ample bracketings so you will see what film does. Also use spot meter to know how different subjects are recorded at different local over/under exposures.

Best way to learn how to use a film is bracketing and spot metering, when we know how the stuff worksn then we may use automatic exposure modes. We also have to learn how our automatic modes work to understand what the camera is to do in auto mode, so we may adjust a compensation in advance, when shooting has to be agile.

It should be noted that Matricial mode knows what kind of latitude our film has, from DX code, so a proper exposure can be calculated for our particular film, but for this we have to select ISO in DX mode, if we set a particular ISO then Matricial mode may not use the Latitude code in the DX information.

Still generally overexposing should not be recommended, we may want to conserve textures in powerful glares and the like, so the good recommendation is to abuse film to learn, and knowing what we did by checking with the spot meter, at least to learn what a film is.

bernard_L · Jan 2, 2020

138S said:
Let me add that in fact ISO rating does not tell were the meter point is

And neither does the Kodak document '...sensitometry_workbook.pdf', that assumes you have a focal plane meter calibrated in lux (well, actually I have a luxmeter somewhere, but the sensor is too large to fit in the focal plane of a 35mm or even MF camera). But the other document that you mention provides this equation:

and I should be able to compute the illuminance (lux) in the focal plane from the scene luminance L (cd/m2) and the f-umber N, thus relating lightmeter indications to lux-seconds.
Same Wiki article on lightmeters gives some interesting information on the gray card reflectance that gives consistent substitute for an incident light meter. Much better than what I previously read in some discussion threads, like, "white (100%) is zVIII, therefore middle grey, zV must be 100/8=12.5%". Btw, my Sekonik gives consistent incident and reflected readings when using a gray card measured to be 18%.

I'm afraid the discussion is now off the thread topic; but at least for me quite interesting.

138S · Jan 2, 2020

bernard_L said:
I'm afraid the discussion is now off the thread topic; but at least for quite interesting.

Not totally OOT

...perhaps before speaking about exposure we should see how we visualize an meter

In ZS that debate about 3.3 or 4.3 stops still generates confusion !

138S · Jan 2, 2020

dylan77 said:
Do you guys agree with this?

Just I remmembered this side by side:

http://canadianfilmlab.com/page/30/

faberryman · Jan 2, 2020

Overexposing by one stop is not normal. Shooting at box speed is normal. There are reasons why you might want to overexpose by one stop, but that would be an exception and not the rule.

LolaColor · Jan 2, 2020

Here's a Colorchecker shot on Portra 400 at one stop increments from three stops under to six over and then scanned on a Noritsu. Density was corrected so that the middle grey patch D4 equates to 118 sRGB, but all scans have the same colour balance of the zero exposure so the natural colour shifts of the film are preserved. Under this workflow, Portra 400 gives orange shadows and magenta highlights. There is great room for overexposure although the highlights do start to compress at around 5 stops over. The brightest colour is at 2 stops over.

Sorry for the long image

138S · Jan 2, 2020

faberryman said:
Overexposing by one stop is not normal. Shooting at box speed is normal. There are reasons why you might want to overexpose by one stop, but that would be an exception and not the rule.

Frank, do you shot C-41 ? just see the color checkers that are under your post !!!!!

Why overexposing ? Well, that color checker at -2 tells it... if your scenes have shadows at -2 you have a degradation there, but at +4 you don't have a degradation. So if your scene has shadows better to ensure that those are well exposed, because some overexposure in the rest of the scene won't harm.

It also depends on if you need film speed of not. Say that we shot outdoors in the sun with a VR lens at f/2.8, we may not need the film speed... then overexposing is feasible.

At the end it's about balancing exposure to get best results, but as overexposure does not harm (with portra / fuji pro) you may often want to overexpose to get a good depiction in the shadows.

On any doubt ask José Villa...

foc · Jan 2, 2020

faberryman said:
Overexposing by one stop is not normal. Shooting at box speed is normal. There are reasons why you might want to overexpose by one stop, but that would be an exception and not the rule.

+1

138S · Jan 2, 2020

foc said:
+1

When you have areas at -2, which is a pretty common situation, 1 stop overexposure is almost always benefical with porta and Fuji pro C-41. There are more times that +1 is benefical than the counter, if not needeing the speed, so overexposing +1 is not the rule but close.

Many Pro photographers that have been shooting C-41 says that.

I can recommend you this book, that concludes also the same:

dylan77 · Jan 2, 2020

LolaColor said:
Here's a Colorchecker shot on Portra 400 at one stop increments from three stops under to six over and then scanned on a Noritsu. Density was corrected so that the middle grey patch D4 equates to 118 sRGB, but all scans have the same colour balance of the zero exposure so the natural colour shifts of the film are preserved. Under this workflow, Portra 400 gives orange shadows and magenta highlights. There is great room for overexposure although the highlights do start to compress at around 5 stops over. The brightest colour is at 2 stops over.

Sorry for the long image

Wow that’s great!

MattKing · Jan 2, 2020

138S said:
Well, that color checker at -2 tells it... if your scenes have shadows at -2 you have a degradation there, but at +4 you don't have a degradation.

At +4, you may start to see highlights degrading instead.
ISO speeds are more closely related to highlight rendition than shadow rendition.
ZS speeds are more closely related to shadow rendition than highlight rendition.
For most viewers, un-manipulated prints or scans with poor (no detail) highlights look worse than prints with poor (no details) shadows.
If you want your prints (or scans) to come back from the lab looking pleasing, use box speed.

138S · Jan 2, 2020

MattKing said:
At +4, you may start to see highlights degrading instead.
ISO speeds are more closely related to highlight rendition than shadow rendition.
ZS speeds are more closely related to shadow rendition than highlight rendition.
For most viewers, un-manipulated prints or scans with poor (no detail) highlights look worse than prints with poor (no details) shadows.
If you want your prints (or scans) to come back from the lab looking pleasing, use box speed.

Matt, it is true, if overexposing an scene by +4 and highlights end at +6 then a degradation would be there.

But if we overexpose in a way that no area in the scene is beyond +4 or +5 then for sure we won't have any loss (with Portra / Fuji Pro C-41)

C-41 film has way more latitude in the highlights than in the shadows, as those color checker tests show, so very often the well balanced exposure is in the overexposure side, because we can get better shadows without damaging highlights.

Of course with velvia it's the counter, better not overexposing much because we easily blow the highlights.

If you see previous posts I was not recommending a blind overexposure by routine, but "If we have deep shadows that we want to record then that safety factor is good, if we don't have those deep shadows then that safety factor is way less necessary."

https://www.photrio.com/forum/threads/is-overexposing-1-stop-normal.172118/page-2#post-2240159

Anyway in pratice I find myself overexposing Portra in the mediterranean strong light, which is a bit like in California. You in Vancouver have different light https://en.wikipedia.org/wiki/Climate_of_Vancouver , only two relatively sunny months and 170 days per year with rain, I have 46 days average with rain, so you may find milder illumination.

A bit Portra likes sun, if you see Villa's (and others) work it's crazy overexposed with impressive results: https://josevilla.com/

NortheastPhotographic · Jan 2, 2020

Rating recommendations by film stock:

400H: 100

Portra 400: 320
Portra 160: 125
Ektar 100: 100
Portra 800: 400-640

XP2 Super: 200.

The Portras don't need over exposure like 400H does, or like NC/VC used to. They're just great films. While they are correctable as you go over more and more, there is a slight color cast and no added benefit. It can be peace of mind though knowing you are getting a good exposure.

138S · Jan 2, 2020

NortheastPhotographic said:
Rating recommendations by film stock:

400H: 100

Portra 400: 320
Portra 160: 125
Ektar 100: 100
Portra 800: 400-640

XP2 Super: 200.

The Portras don't need over exposure like 400H does, or like NC/VC used to. They're just great films. While they are correctable as you go over more and more, there is a slight color cast and no added benefit. It can be peace of mind though knowing you are getting a good exposure.

Well, the Fuji 160NS and the Portra 160 have very similar shadows, but in the 400 speed there is a difference, with the Fuji requiring more light like you say. Instead in the 160 speed both are the same.

Is overexposing 1 stop normal?

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