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07-15-2009, 08:52 PM   #1
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Ektar Exposure Tests (+2 to -2 stops)

There has been quite a bit of recent discussion regarding Ektar 100 and the film's characteristics. Items of discussion have included:
  • Appropriate shooting ISO (rated vs. over vs. under)
  • Affect of development: grain, colors, contrast, etc
  • Wild colors (red in particular going to various fluorescent tones)

While I am not prepared to do a comparison between processing labs, I was willing to sacrifice a few frames of my most recent roll to do a controlled study to see the affects of over/underexposure plus or minus 2 stops of the rated ISO in both shade and open sun.

Methodology

Exposure
  • Pentax KX, recently CLA'd by Eric Hendrickson
  • Pentax-M 50/1.7 set at f/5.6
  • Internal meter set to rated ISO (100)
  • Shade series was done in open shade (north facing sky) on a cloudless sunny day
  • Sun series was done in open sun on a cloudless sunny day
  • Camera was tripod mounted for all shots over a 1.5 minute period for each series
  • Exposures were made at the meter-indicated settings and at +2, +1, -1, and -2 stops, using the shutter to change exposure

Processing
  • Machine processed by the pro lab at Blue Moon Camera in Portland, Oregon
  • No special instructions or treatment

Scanning
  • Nikon Coolscan 5000 ED
  • 1,100 dpi resolution
  • Auto focus for each frame
  • Auto exposure for each frame

Post Processing
  • Minimal post-processing in Lightroom limited to exposure adjustment for equivalent values of white highlights

Results

Comparison matrix with shade series on top and sun series below



I will add larger version of each image to separate posts along with a summary.

Steve


Last edited by stevebrot; 07-16-2009 at 10:39 AM.
07-15-2009, 09:05 PM   #2
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Shade Series, larger versions

+2 Overexposed

Name:  0714_023.jpg
Views: 6158
Size:  354.7 KB

+1 Overexposed
Name:  0714_024.jpg
Views: 6100
Size:  391.7 KB

Rated ISO
Name:  0714_025.jpg
Views: 6065
Size:  432.7 KB

-1 Underexposed
Name:  0714_026.jpg
Views: 6364
Size:  457.2 KB

-2 Underexposed
Name:  0714_027.jpg
Views: 6053
Size:  482.8 KB
07-15-2009, 09:07 PM   #3
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thanks for the tests ... i dunno, the colours just don't look right on any of them
07-15-2009, 09:09 PM   #4
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Sun Series, Larger Versions

+2 Overexposure
Name:  0714_029.jpg
Views: 6062
Size:  419.8 KB

+1 Overexposure
Name:  0714_030.jpg
Views: 5977
Size:  451.3 KB

Rated ISO
Name:  0714_031.jpg
Views: 6079
Size:  507.9 KB

-1 Underexposure
Name:  0714_032.jpg
Views: 5979
Size:  522.2 KB

-2 Underexposure
Name:  0714_033.jpg
Views: 5969
Size:  552.3 KB

07-15-2009, 09:27 PM   #5
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Great work, thanks! I kind of like the +1 overexposed shots the best.

Phil.
07-15-2009, 09:31 PM   #6
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Thanks for the test Steve.
I have been spending quite a bit of time scanning ONE roll of Ektar.
And I also found simply by changing the parameter while scanning that the color could vary widely from decent to interesting to damn ugly.
I am seriously considering giving up on Ektar for Elitechrome instead.
To some extend I had more success with full sun shots than evening or shaded.

BTW I have been exposing the shots based on either Pentax Spotmeter or Gossen Incident meter....




Cheers,

Luc
07-15-2009, 09:37 PM   #7
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Summary/Conclusions

Over-exposure
  • Significant decrease in contrast, particularly in bright colors
  • Loss of color saturation
  • Loss of highlight transitions in the reds in bright light at even +1 over
  • Insignificant color shift
  • +1 provides a nice boost in shadow detail

Under-exposure
  • Significant increase in contrast, again the affect is more pronounced with bright colors
  • Exaggerated saturation
  • Significant color shift towards the magenta end
  • Insignificant increase in highlight texture

Discussion
As mentioned in various earlier threads and elsewhere on the Web, this film seems to have its sweet spot at the rated ISO. That being said, there is some benefit to mild over-exposure, though there may be a loss of tonality for some high values. 0.5-1.0 stops over at the max would be my suggestion. The loss of contrast and tonality with additional overexposure beyond +1 is unacceptable.

Edit
I thought it useful to add these two comparison crops from the 1+ sunny (on the left) and ISO 100 sunny (on the right) shots. They show the tonality and contrast effect of mild overexposure quite nicely.

Name:  1plus_crop.jpg
Views: 5868
Size:  21.0 KBName:  rated_crop.jpg
Views: 5894
Size:  24.5 KB

Here is a comparison of the +1 sunny (top) and ISO 100 sunny (bottom) histograms from Lightroom...

Name:  histograms.gif
Views: 5896
Size:  8.2 KB

End edit

In these tests, I was unable to produce the bizarre fluorescent reds seen on some posted photos (mine included). An early comment to this thread indicated that "none" of the colors look right. I agree that some tweaking would be in order for both the reds and the blues in the scanner settings. The scanner was set to default response curves and has not yet been dialed in for Ektar. The expected colors:
  • The bandana is new and is bright true red
  • The Adidas shorts are a true royal blue
  • The glass dish is a deep emerald green
Of the three colors, the green is the most correct. The blues need a saturation bump while the reds need a mild shift in hue. I think I may have a shot of the setup taken with the K10D. That should give reasonable a color reference if I can find it.

Steve

Last edited by stevebrot; 07-15-2009 at 10:54 PM.
07-15-2009, 09:51 PM   #8
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That was quite enlightening. I just finished my first Ektar roll today, everything is at the rated exposure. I'll see how I can improve the shots relative to this experiment

07-16-2009, 02:57 AM   #9
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Althought I still can't buy this film in Canada I will some day and your test is very helpful.
While perusing through a Flickr! group (of Ektar) I noticed several of the hidious red photos you mentioned and that is cause for concern.

I favour the '0' or '+1' settings overall.

Thanks for taking the time and effort to conduct this test.
07-16-2009, 03:34 AM   #10
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What's strange seeming to me is the sun/overexposed avoid blowing out details in bright spots, while rated and under-exposed blow the highlights something wicked.

Of couse there's the scanner auto exposure to contend with - the wider the negative latitude the more it pushes the scanner's highs... with the +1 the highest highlight gets the nod, then there's a slight gap to where the tones start. That may be an advantage. I've been meaning to go back and manually scan a couple of problem negatives, with the widest scanner latitude, produce very flat seeming scans, and then see what photoshop can do.

When I shot my three rolls of ektar, I found that an unfortunate coincidence of three factors served to produce over-exposed and detail-free scans of flower shots: 1) the meter on many Pentax cameras maybe slightly color influenced (ie. under reports bright yellows e.g.) and shadow-biased, 2) ditto ektar 3) ditto photographer (me) being lazy and/or not conscious enough when doing these photographs. How hard is it to dial in exposure comp on auto cameras or take two readings with a KX?? but there you have it. The auto exposed scans don't help either.

But thank you for the very interesting and edifying series, I'm somewhat surprised by the evidence.
07-16-2009, 07:27 AM   #11
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It seems to from a slight green bias overexposed to a distinct magenta one.

Nice. The overexposed one looks like a under-saturated slide film. Solid, but smooth.
07-16-2009, 07:58 AM   #12
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excellent post!

i am intrigued that the effect of over/under exposure with film is radically different with that of digital!
07-16-2009, 08:12 AM   #13
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QuoteOriginally posted by J.Scott Quote
Althought I still can't buy this film in Canada I will some day and your test is very helpful.
While perusing through a Flickr! group (of Ektar) I noticed several of the hidious red photos you mentioned and that is cause for concern.

I favour the '0' or '+1' settings overall.

Thanks for taking the time and effort to conduct this test.
KODAK EKTAR 135-36 36EXP 100ISO

they ship canada wide...
07-16-2009, 08:19 AM   #14
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QuoteQuote:
Althought I still can't buy this film in Canada I will some day and your test is very helpful.
While perusing through a Flickr! group (of Ektar) I noticed several of the hidious red photos you mentioned and that is cause for concern.

I favour the '0' or '+1' settings overall.

Thanks for taking the time and effort to conduct this test.

If you live close to Vancouver there is a photo shop that carries Ektar at $4.99 a roll.
07-16-2009, 08:33 AM   #15
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This is an excellent film. I certainly consider the results of extreme over-exposure more desirable than slight under-exposure. That purple tone in the shadows is disgusting, and I've had the misfortune to experience it. I personally rate it at ISO 80 in my meter, and box speed in my camera. Speaking of meters: this test would be even better (and it's very nice as it is!) had you exposed it with an external light meter. My tendency is to trust an external meter's readings over those of a camera's. Of course, I may be jumping to conclusions, as I don't know if you used the camera's spot meter to zone the scene (if your camera has one). Can you also please shed some light on what software you used to scan the negs? Was it Nikon Scan 4, Vuescan, or something else? My experience with the first two is that they give wildly different results.
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