Tutorial for Sekonic L-758DR: How to create a custom profile

Hello all,

First let me say thanks to the original poster of the tutorial. I havent bought the meter yet I am just finalizing my research as my Minolta flash meter III died recently. Has anyone tried to determine if the chip values from the Sekonic chart are duplicated on a Kodak Q13 color seperation chart set?
http://www.amazon.com …Guide-Scale/dp/B00009R7G9 This set has color seperation chips as well as a stand alone greyscale. I find it hard to believe that the Sekonic chart is so custom as to not have the same values available on other more standardized charts. Also one of these other charts are much less expensive and more useful as well.

Thank you

Rick

Rick wrote in post #4880790
Hello all,

First let me say thanks to the original poster of the tutorial. I havent bought the meter yet I am just finalizing my research as my Minolta flash meter III died recently. Has anyone tried to determine if the chip values from the Sekonic chart are duplicated on a Kodak Q13 color seperation chart set?
http://www.amazon.com …Guide-Scale/dp/B00009R7G9 This set has color seperation chips as well as a stand alone greyscale. I find it hard to believe that the Sekonic chart is so custom as to not have the same values available on other more standardized charts. Also one of these other charts are much less expensive and more useful as well.

Thank you

Rick

Hi Rick,

If you can find something with 1/6 stop patches you're in business. That's all that's required.

Thanks Ill be trying it out as soon as I get the meter which has been orderd!

Thanks again for the tutorial

Rick

Profile with Stouffer 41 step wedge?

TMR Design wrote in post #4875041
In any event, I haven't seen or heard of another target or gray card with the 1/6 stop patches.

Hello again Robert. Today I ran across the Stouffer 41 step (1/6 stop) transmission wedge seen here ...

http://www.stouffer.ne​t/TransPage.htm

The item T4105 has 41 steps at 1/6 stop (or 0.05 density) increments. It measures 1"x9". Cost is $24, or calibrated for $40 and both calibrated and certified for $110. What is your advice on the suitability of the two lower cost wedges for profiling? As a reference Phil & Co at DPReview use the calibrated Stoffer 1/3 stop x 41 increment wedge to collect exposure data for their reviews.

If I understand the profiling process, the Sekonic wedge has 6 x 1/6 stop increments requiring about 13 exposures to collect the required information. However the Stouffer wedge covers 6 1/2 stops and so would require only two exposures to collect the same information. Is this correct?

Thanks.

-jts

PS. The $20 Kodak Color Separation Guide with Grey Scale, 8" Size, #Q-13 mentioned in another post has 0.10 density or 1/3 stop increments. However it might still be a lower cost alternative to the $67 8-1/2" x 11" Gretag Macbeth Color Checker Exposure Target for post processing color correction. I have also read that Kodak outsourced this color guide to Tiffen and is no longer considered a reliable target.

[Later] Stouffer wedge is transparent and Phil backlights it for his purposes. I'm not sure how this affects our purposes. More to consider, certainly. If ones goes to the test section of a recent dSLR, say the Canon 40D, and then to the Photographics Tests section for DR, at the start of this section you will see Phil's methods, including reference to the Stoufer 1/3 stop wedge. See here ...

http://www.dpreview.co​m …ws/canoneos40d/​page20.asp

Hi jts,

I'm not an expert but I believe you should be able to use the Stouffer strips. Other than the Sekonic card having a gray card on the back and being larger I can't imagine there's anything different. I would guess that since the Stouffer is being marketed and used for exposure that it is neutral and no more reflective than the Sekonic.

Unless anyone can think of a reason why it would not work I think it's a safe bet and may turn out to be a great alternative for those that don't want to buy a Sekonic calibration target for $100.

If the reflectivity values are given you can directly compare the swatches. Sekonic has the values published but if you can't find them, myself or someone else with the documentation can give them to you.

Please let use know what you do and how it works out.

Stouffer reflectivity data

TMR Design wrote in post #4948863
Hi jts,

I'm not an expert ...

I appreciate your modesty!!!

TMR Design wrote in post #4948863
If the reflectivity values are given you can directly compare the swatches. Sekonic has the values published but if you can't find them, myself or someone else with the documentation can give them to you.

Please let use know what you do and how it works out.

Here are the published reflectivity specifications ...

http://www.stouffer.ne​t/T4105spec.htm

Note that step 16 out of the 41 steps is at 18% reflectance. In passing, step 19 is a 12.5%. I mention the latter because some recommend 12% as the neutral point for digital sensors.

If the calibrated version at $40 is good enough for Phil (DPReview) then I suppose it's good enough for me. It may actually be that generally the $24 uncalibrated version is sufficiently accurate. However, given the cost of the Sekonic it seems a bit extremet to pinch pennies over the wedge to be used for calibration of the meter!

I will sleep over this but likely order the $40 calibrated version. As a thought it is possible that someone has already performed this experiment as Stouffer is apparently a known entity. That someone may have shared the suitability of the Stoffer wedge on the web ... if we are exceedingly lucky!

-jts

HI jts,

I think getting the calibrated version makes a lot of sense. After all, we are talking about calibrating a meter to give you accurate readings based on the characteristics of your camera and sensor. If you're going to the trouble of calibrating and see 1/10 stop accuracy as important then it wouldn't make much sense to do half-ass it.

Stouffer wedge

TMR Design wrote in post #4950978
... getting the calibrated version makes a lot of sense.

Yes, I agree. The uncalibrated version may partially result from calibration rejects when checked for all I know, which would make it a bit foolish for the reaons you outlined.

One niggle. The Stouffer wedge is transparent and Phil backlights it for his purposes. I'm not sure how this affects our purposes. More to consider, certainly. If ones goes to the test section of a recent dSLR, say the Canon 40D, and then to the Photographics Tests section for DR, at the start of this section you will see Phil's methods, including reference to the Stoufer 1/3 stop wedge. See here ...

http://www.dpreview.co​m …ws/canoneos40d/​page20.asp

Hey folks, lots of good info here! It's been immensely helpful.

I just got one of these meters and it's really nice... I'm loving it... I'm just a bit disconcerted by the results of my profiling. It seems my 5D is exactly one stop too dark. I mean EXACTLY. When I sample the patches shot at 5.6, the center grap patch is exactly 118 in the green channel. On the F8.0 shot, it's 83, one stop too dark.

Is it at all possible that my 5d could be randomly off by one full stop?

I discovered this when I exposed for F8 and then bracketed. I my images didn't reach the white clipping point at F2.8, at any ISO setting! To make sure it wasn't my meter, I grabbed a friend's Rebel and shot some test exposures with it... it's dark by about 1/3 stop, nowhere near as dark as my 5D.

It's bumming me out a bit, actually... I've had the 5d for a while and wonder if that kind of variation even falls under Canon's 'out of spec' classification and would prompt them to fix it. Sigh. It's probably not even under warranty at this point. The only hope I have is coming from the highly suspicious nature of a 'perfectly' wrong setting of one full stop too dark. Maybe it's the firmware or something.

PKMousie wrote in post #4954200
I just got one of these meters and it's really nice... I'm loving it... I'm just a bit disconcerted by the results of my profiling. It seems my 5D is exactly one stop too dark. I mean EXACTLY. When I sample the patches shot at 5.6, the center grap patch is exactly 118 in the green channel. On the F8.0 shot, it's 83, one stop too dark.

Is it at all possible that my 5d could be randomly off by one full stop?

I'm not sure that a patch reading of 83 represents a full stop (measuring from 118) but however, I would expect the centre patch to be a full stop darker on your f8 sample if the f5.6 sample was spot on?

No offense meant here, as maybe I have just misread your post, but I would suggest user error here. If your 5D was a full stop out - intermittently or not, I'm sure you would have noticed this before buying the L-758.

steveathome wrote in post #4954839
I would suggest user error here. If your 5D was a full stop out - intermittently or not, I'm sure you would have noticed this before buying the L-758.

That's what I'm hoping for, actually. I have a hard time believeing that the offset would be so precice!

Unfortunately, I was not in a good position to notice an issue like this before, since I was never able to correlate a known light level to the resuts in camera. Up until now I've been shoting mostly ambient light metering off of common objects that I know will produce a decent exposure by using the camera's spot meter, or shooting flash using ETTL and letting the camera decide how much light is enough. Neither of those workflows lends itself to objective measurement like my recent move to all manual off-camera flash measured with a meter.

My best guess for the cause (if NOT the camera) is the settings I'm using to convert my RAW files in ACR. I've been following the suggestion to zero out the sliders, and I've been zeroing out the brightness setting as part of that; it's normally at 50. This doesn't seem right, but I'm pretty sure it was mentioned in the discussion, so I did it. After testing, if I leave it at 50, well... the middle gray exposure is correct.

Here's hoping it's user confusion/error! That would be SO much better than faulty equipment, eh? In the normal case when zeroing settings in ACR, should I stick to exposure, shadows, contrast, saturation, and a linear curve, or does brightness need to be adjusted as well? If brightness should be zero in ACR, I'm in trouble.

Of course, if it should be left at 50, my friend's camera is still objectively 2/3 of a stop brighter, a situation I'd trade for too dark any day!

USEFUL TIP #1: It's very important to calibrate your camera for the ISO you're shooting prior to taking readings for custom profiling.

The simple process for doing this is to set up your gray card and take a shot at the standard value (typically f/8 ). Then look at that image in Photoshop. You want your gray card (18% reflectivity) to give you a value of 118 on the green channel. Make the necessary adjustment in Photoshop (or Lightroom or your RAW editor) until is it at 118. Then plug that offset into your camera and shoot the card again. Look at that image in Photoshop to make sure you're now reading 118 from the gray card. Since you can only adjust aperture in 1/3 stops, get it as close as possible.

You can now enter that offset as a working ISO or as a Calibration Adjustment on the meter but this is not the best way because you'll be adding a global offset rather than offsets for each ISO. I know, it means more work taking all those shots at different ISO's but if you were looking for an easy way out you wouldn't have gotten this meter .

So.. remove the offset from the camera (but write it down or remember it), return to f/8 for standard exposure and continue to shoot the images for custom profiling, and following USEFUL TIP #2 below.

Thanks very much for posting these instructions. I've read through all six pages of this thread and still have a few questions. I'm embaressed to say my primary use of my Sekonic here to fore has been to trigger my pocket wizard. My primary goal is to use it for landscape photography with my D3. It's probably overkill to profile the Sekonic for this use, but I already bought the target so I'm going through with it.

In regards to your Tip 1, am I correct in assuming that one must set an aperture and then adjust shutter speed to center the light meter in the camera? When I bring the raw file into ACR do I need to care about white balance or any other setting? I'm thinking some should be zeroed out. Should I also disable my color caibration that I did for the camera. If it's not 118, what should I adjust? I'm thinking exposure. If it's exposure, then how is that number translated to stops? Finally, assuming that I need an offset and I'm trying to profile the camera for IS0 200, do I set the camera to that ISO to take the target shots and select the ISO in the Sekonic software that reflects the offset.

On a different tangent, how does one shoot the targer for ambient reflected light (I think I got that right)? Would I just put the target in sunlight?

Thanks in advance for your indulgence,
Curt

cortes wrote in post #5030632
Thanks very much for posting these instructions. I've read through all six pages of this thread and still have a few questions. I'm embaressed to say my primary use of my Sekonic here to fore has been to trigger my pocket wizard. My primary goal is to use it for landscape photography with my D3. It's probably overkill to profile the Sekonic for this use, but I already bought the target so I'm going through with it.

In regards to your Tip 1, am I correct in assuming that one must set an aperture and then adjust shutter speed to center the light meter in the camera? When I bring the raw file into ACR do I need to care about white balance or any other setting? I'm thinking some should be zeroed out. Should I also disable my color caibration that I did for the camera. If it's not 118, what should I adjust? I'm thinking exposure. If it's exposure, then how is that number translated to stops? Finally, assuming that I need an offset and I'm trying to profile the camera for IS0 200, do I set the camera to that ISO to take the target shots and select the ISO in the Sekonic software that reflects the offset.

On a different tangent, how does one shoot the targer for ambient reflected light (I think I got that right)? Would I just put the target in sunlight?

Thanks in advance for your indulgence,
Curt

I figured out what to do with the offset: use tip #2

Hi Curt,

Since the writing of this tutorial I've spoken to Sekonic and learned a lot more about the process of creating custom profiles.

I really should edit the tutorial because as it turns out, Tip#1 can be skipped entirely. The process of creating the custom profile takes care of that and the Compensation value written into the profile is the offset you would/should have arrived at if you did the calibration by itself.

TMR Design wrote in post #5032389
Hi Curt,

Since the writing of this tutorial I've spoken to Sekonic and learned a lot more about the process of creating custom profiles.

I really should edit the tutorial because as it turns out, Tip#1 can be skipped entirely. The process of creating the custom profile takes care of that and the Compensation value written into the profile is the offset you would/should have arrived at if you did the calibration by itself.

It was a useful exercise. My D3 appears to be off by about a third of a stop.

In your original post, you spoke of entering the meter reading into the Light Meter Measurement fields. For reflected/ambient I would assume I would take a reading off the target at whatever f stop I'm starting with. Would I set the camera to the same setting or set it to whatever shutter speed centers its meter? I would think I would, but I just wanted to double check


Also any thoughts on where I should place the target (direct sun, shade,etc.)?

Curt