Luminous Landscape Forum

Equipment & Techniques => Beginner's Questions => Topic started by: Thenolands on September 06, 2017, 01:07:42 am

Title: Prints too dark but monitor calibrated
Post by: Thenolands on September 06, 2017, 01:07:42 am
I am doing some amateur art reproduction work but my prints are coming out too dark. Before 1000 people post telling me my monitor is too bright let me explain my setup. Shooting with Pentax 645z, printing on ipf8400, screen calibrated with Spyder 5, exposed the image according to in-camera light meter using gray card in same light as artwork, using custom color profile created using colorchecker passport. I feel like my monitor and print match pretty well but my issue is why is it too dark if I am not editing the photo and it is supposedly a properly exposed image? Again, I am not viewing on a bright screen and reducing the exposure in post. I am not adjusting exposure at all. It doesn't seem like I should have to increase my exposure in post production just to get a proper image printed.
Title: Re: Prints too dark but monitor calibrated
Post by: BobShaw on September 06, 2017, 01:33:25 am
Could be lots of things.
First is it correctly exposed? If you don't know if it correctly exposed then you are on the back foot. What does the histogram show? Is the histogram for the grey card image in the centre of the histogram? Did you adjust levels or something similar? As you move the mouse over the image do the highlights read about 220+ on the Digital Color Meter or in the application?
At the end of the day, if the subject is dark, the print will be dark.

Also there is no such thing as "amateur art reproduction". There may be reproduction of amateur art, but Art Reproduction is a complex thing.
Title: Re: Prints too dark but monitor calibrated
Post by: Dave Rosser on September 06, 2017, 07:08:18 am
I am doing some amateur art reproduction work but my prints are coming out too dark. Before 1000 people post telling me my monitor is too bright let me explain my setup. Shooting with Pentax 645z, printing on ipf8400, screen calibrated with Spyder 5, exposed the image according to in-camera light meter using gray card in same light as artwork, using custom color profile created using colorchecker passport. I feel like my monitor and print match pretty well but my issue is why is it too dark if I am not editing the photo and it is supposedly a properly exposed image? Again, I am not viewing on a bright screen and reducing the exposure in post. I am not adjusting exposure at all. It doesn't seem like I should have to increase my exposure in post production just to get a proper image printed.
I find Canon Printers print dark at default settings. You can adjust print brightness in the printer driver,  I find I have to apply 20 brightness adjustment to my Canon Pro 100 to get a satisfactory print brightness even though I have a fully colour managed workflow. If you are using Lightroom you can adjust the brightness in the Lightroom print module rather than the printer driver.
Title: Re: Prints too dark but monitor calibrated
Post by: nirpat89 on September 06, 2017, 08:11:01 am

I am doing some amateur art reproduction work but my prints are coming out too dark. Before 1000 people post telling me my monitor is too bright let me explain my setup. Shooting with Pentax 645z, printing on ipf8400, screen calibrated with Spyder 5, exposed the image according to in-camera light meter using gray card in same light as artwork, using custom color profile created using colorchecker passport. I feel like my monitor and print match pretty well but my issue is why is it too dark if I am not editing the photo and it is supposedly a properly exposed image? Again, I am not viewing on a bright screen and reducing the exposure in post. I am not adjusting exposure at all. It doesn't seem like I should have to increase my exposure in post production just to get a proper image printed.

Agree with Bob on reproduction photography being a very difficult thing.   A project taking pictures of antique wall papers once made me realize how much.

With the problem at hand, my sense is that the mismatch is something to do with the use of the grey card. The grey card, used conventionally in the way it was used in a film camera, will symmetrically push the exposure within the dynamic scale of the film or the sensor.  The result is that the photograph is "properly" exposed, but it is "correctly" exposed?  I would say it depends on how you light up your subject.  If you do an experiment and vary the amount of light falling on your painting (I am assuming that's what your are reproducing) and take several shots each using the grey card as your exposure guide, the resulting photographs will all look the same.  So even though you made no change in post-processing, only one of those photograph, if that, will match the intensity of the original subject.  So by not doing any editing, you actually end up with an inexact reproduction.  In your particular case, you got darker outcome because the artwork is well-lit, as usually is, and the camera wants to normalize it to 18% grey.  Looking at it another way, if you take a picture of a dark room using grey card, you end up with a light room.

Considering that there is no mismatch between the monitor and the print, you can pretty much use the monitor to do the final adjustment.  Light your painting as it would normally be lighted in display where you can see it side by side with your monitor, preferably with the same color temperature as your monitor calibration.  Then using something like Levels adjustment with the middle grey slider, darken or lighten to match the monitor and the painting to your satisfaction.  Print and hopefully you will be much closer than before.

Does that make sense?

:Niranjan.
Title: Re: Prints too dark but monitor calibrated
Post by: Thenolands on September 06, 2017, 08:23:51 am
@BobShaw: I get it is complex. That is why I am in the newbie section asking questions. To your other comments, to get a histogram of the gray card I assume I have to take a shot containing only the gray card or can I crop to include only the gray card?

@Niranjan: forgive me but I thought the point of the gray card was to eliminate the fact that the light sensor in camera wants to make everything 18% gray and thus normalize the exposure regardless of how well or dimly lit the subject is. No? If not, are you saying I should back the lights far enough off the art that it is not so intensely lit? I am afraid this would result in poor light coverage of the piece (again, I don't have a $100k setup)

Also, failed to mention that I already have +20 brightness selected in Lightroom just to get print to match monitor. With the painting I am currently working on, I got the print to match just about spot on (to my amateur eye) when I increased the exposure in Lightroom by 1.0. That seems to be ALOT to me. So,one, I don't feel that should be necessary to match the print and two, I worry about artifacts similar to high ISO if I am constantly artificially boosting exposure
Title: Re: Prints too dark but monitor calibrated
Post by: farbschlurf on September 06, 2017, 09:09:08 am
You might be interested in this
https://www.dpreview.com/forums/thread/2938408#forum-post-37440432
scroll down a bit.
Actually I started to use a lightmeter for such tasks (which were much more amateur-like, than yours ...)
Title: Re: Prints too dark but monitor calibrated
Post by: nirpat89 on September 06, 2017, 09:13:32 am
Use of grey card and taking a reading and calculating the exposure is not very different from the camera taking readings at many different spots (based on settings chosen,) averaging it and calculating the exposure.  The latter is simply based on a variety of colors and points of different reflectivities rather than just one (grey) color and 18% reflectivity.   Both, if done properly, try to put the image within the capability of the film or the sensor without caring for what the scene looked like.

The way I would do is ditch the grey card (unless it is color neutral and you are using it to correct the color-cast in post, in which case you can just take a separate picture of it) and use the camera histogram as your guide for exposure - making sure the it does not exceed on either side.  You do not have to compromise on the light, do the best you can so get a even exposure without reflections.  Then adjust the level of brightness in an application by comparison with the artwork lighted in the same way as it would in normal viewing circumstances.  The last step is not to rectify the failure of the exposure but necessary to arrive at the correct brightness level for viewing.
Title: Re: Prints too dark but monitor calibrated
Post by: Christopher Sanderson on September 06, 2017, 10:14:09 am
Quite often the 'My print is too Dark! problem' is caused by perception - especially if you are judging the file brightness against a black background on your profiled monitor and then using a white border or mat for the print. You might start by changing the background against which the file is seen in Lightroom to White and reducing the size displayed so there is lots of white surround.

Let's try to diagnose the issue. Would you please take a screen grab of the histogram of the actual file that you are printing (not the camera original). Also if you know how*, use the LAB read-out in Photoshop to measure the brightness (L) of various tones within your file, picking an 'average' light tone, midtone and darktone. Let us know what the readout is. Just give us the L readout for now and ignore the a b

* Control/Right click the eyedropper in the Info palette

It is possible that a simple curve adjustment is all that is needed.
Title: Re: Prints too dark but monitor calibrated
Post by: Thenolands on September 06, 2017, 12:06:35 pm
I will work on uploading a pic today.

On a semi-related note, for those of you who do some art reproduction work, if you have a customer that wants a print of an oil painting printed on canvas, do you go with a luster coated canvas or matte? Luster always seems to have far better vibrancy and depth similar to the oils painting but it seems many of the quality canvases available are matte.
Title: Re: Prints too dark but monitor calibrated
Post by: HSakols on September 06, 2017, 03:23:27 pm
In this video Charlie Cramer talks about prints and perception.  He also gives some great examples.
https://www.onlandscape.co.uk/2017/08/charles-cramer-landscape-photography-conference/
Title: Re: Prints too dark but monitor calibrated
Post by: nirpat89 on September 06, 2017, 03:49:01 pm
On a semi-related note, for those of you who do some art reproduction work, if you have a customer that wants a print of an oil painting printed on canvas, do you go with a luster coated canvas or matte? Luster always seems to have far better vibrancy and depth similar to the oils painting but it seems many of the quality canvases available are matte.

I haven't done reproduction work but do make prints on matte canvas which at times I brush with a acrylic water-based gloss varnish that imparts luster to it while also giving it a little more depth.  It is good for protection as well.  Something you can experiment with in lieu of a luster canvas. 
Title: Re: Prints too dark but monitor calibrated
Post by: Christopher Sanderson on September 06, 2017, 05:59:45 pm
In this video Charlie Cramer talks about prints and perception.  He also gives some great examples.
https://www.onlandscape.co.uk/2017/08/charles-cramer-landscape-photography-conference/
We will soon be publishing a new video project in the Masters series in which Charlie Cramer gives an expanded version of this lecture. There will be a detailed chapter on Perception.
Title: Re: Prints too dark but monitor calibrated
Post by: Thenolands on September 06, 2017, 07:42:34 pm
okay, going to try to attach screen shots of the histogram of the entire painting and just the gray card. I see the gray card is shifted slightly to overexposed? is that right? so that may make it expose darker? Also attaching histogram of increasing the exposure in post to 1.0 (1 stop?) which prints perfectly and the histogram would tend to agree, no? so what is causing this?

Sorry, this is actually my first time diving into the histogram so don't make too much fun :)

I should also say i am using a custom color profile based on the colorchecker passport if that makes any difference. Just for fun i removed it and used Adobe Standard and of course it changed the histogram but did not shift significantly toward better exposure.
Title: Re: Prints too dark but monitor calibrated
Post by: Christopher Sanderson on September 06, 2017, 09:56:18 pm
It appears that in the original exposure, the vast majority of tones are darker than 50% gray. This suggests that the shot was under-exposed and the print will certainly appear dark without correction. The third screenshot with a one stop increase in exposure certainly looks better. On printing with that correction, how does it compare to the original?
Title: Re: Prints too dark but monitor calibrated
Post by: Thenolands on September 06, 2017, 10:08:37 pm
The 1 stop increase printed near perfect. So, if the light meter read a correct exposure off the gray card, and I didn't change the camera settings and then took my shot, why would my in-camera light meter be off by a whole stop? Is it possible that the in camera light meter is that bad on a 645z? Or is there something in my process that is wrong?

Please don't assume that I did or did not do certain things. I am fairly new at all of this and could be screwing up anywhere, really 😀
Title: Re: Prints too dark but monitor calibrated
Post by: BobShaw on September 07, 2017, 02:14:19 am
okay, going to try to attach screen shots of the histogram of the entire painting and just the gray card.
I should also say i am using a custom color profile based on the colorchecker passport if that makes any difference.
That is not a grey card. As you now advise, it is a colorchecker passport (CCP). So ignore my previous comment on reading the RGB value of the "grey card".
However you do have a tool suitable to do reproduction if you know how to use it. There are White squares on the CCP, they need to be white. Not off white, light grey, dark grey etc.
On your middle photo the white squares are at best mid grey. You need to raise the exposure until these are at least 220 RGB value.

Buy yourself an incident light an flash meter. A cheap one like Sekonic 308 is fine. You can do without it amateur style by taking lots of shots until you get it right or just measure it once. Once you have plenty of experience you may not use it much, but at least you will understand why the camera reading is always wrong unless you are reading the reflected light from a totally grey card. That is all they are calibrated for.

Have a look at these. They are for Hasselblad but will give you an idea. You may buy a Hasselblad after watching.
https://www.youtube.com/watch?v=fxEDn4ueFJE
http://www.hasselblad.com/products/phocus-2-9-colour-calibration/

good luck
Title: Re: Prints too dark but monitor calibrated
Post by: Christopher Sanderson on September 07, 2017, 09:20:13 am
There has been some good advice given here - probably enough for you to now succeed.

On an anecdotal level, I have always found that the basing of exposure/white balance on a gray card or colour checker to be problematic. This likely has to do with my method and the various things that can go wrong between subject, card and exposure. The inference of a colour checker is that it will solve all problems but that alas is far from true - in my experience it gives little more than a guide.

I tend therefore to work on the KISS principle and simply use the simpler methods of my eyes and the numbers that the histogram and the file give me. No, not terribly scientific but if one's method is faulty, a lot less frustrating. I still suggest learning how to use the LAB readouts from PS and LR. These are simple to understand and provide excellent information on your file.
Title: Re: Prints too dark but monitor calibrated
Post by: digitaldog on September 07, 2017, 10:21:44 am
Sorry, this is actually my first time diving into the histogram so don't make too much fun :)


Everything you thought you wanted to know about Histograms


Another exhaustive 40 minute video examining:


What are histograms. In Photoshop, ACR, Lightroom.
Histograms: clipping color and tones, color spaces and color gamut.
Histogram and Photoshopís Levelís command
Histograms donít tell us our images are good (examples).
Misconceptions about histograms. How they lie.
Histograms and Expose To The Right (ETTR).
Are histograms useful and if so, how?


Low rez (YouTube): http://www.youtube.com/watch?v=EjPsP4HhHhE (http://www.youtube.com/watch?v=EjPsP4HhHhE)
High rez: http://digitaldog.net/files/Histogram_Video.mov (http://digitaldog.net/files/Histogram_Video.mov)[/font]


Use a color reference image not your 'dark' image to test this!
http://www.digitaldog.net/files/2014PrinterTestFileFlat.tif.zip
Title: Re: Prints too dark but monitor calibrated
Post by: Thenolands on September 07, 2017, 11:30:11 am
Thanks for all the replies. It is very helpful. i am going to take some more shots of that painting tonight and see how it goes.
Title: Re: Prints too dark but monitor calibrated
Post by: Thenolands on September 07, 2017, 08:09:51 pm
If you had to choose between 55mm or 120mm macro on the 635z which would you choose for art reproduction? I know, I know... you wouldn't, you would use a hasselblad... but if you had to?
Title: Re: Prints too dark but monitor calibrated
Post by: BobShaw on September 07, 2017, 09:10:28 pm
If you had to choose between 55mm or 120mm macro on the 635z which would you choose for art reproduction? I know, I know... you wouldn't, you would use a hasselblad... but if you had to?
Mate, you probably need to say if the art is the size of an A4 piece of paper or 2metres square and if your room is 3m square or 10 metres square.
I doubt that it matters much as the art is only 2 dimensional. I use a 50-110 zoom most of the time because the camera is on a stand and I just fill the frame. What else are you going to do with the lens is probably more important and for most still things I use a 120mm macro in the studio. So I would say that.
Title: Re: Prints too dark but monitor calibrated
Post by: Thenolands on September 08, 2017, 08:55:59 pm
Painting is 12inx12in, room is about 17ft square

I took some more shots without using the gray card. I spot metered off several locations in the painting (the sky, the grass, the road,etc). Obviously, I got some very different readings at each location. I have aperature set at f/8, 100 ISO and I averaged the metering to where the brighter sky read 1/3 stop over exposed and the darker grass and road was 1/3 to 2/3 underexposed. I think the shot has much better exposure.

But, I have a question still about gray card use. It would seem that the gray card I was using has a higher reflectivity than the painting and therefore the exposure for the gray card was underexposed for the painting. So, since very few images have 18% reflectivity, what does a gray card actually do for you?

And another question about using the colorchecker. I created a colorchecker profile in the exact light I was shooting the painting in. If I shoot another painting of the same size such that I don't have to move camera or lights, can I use the same profile? Is there any reason to shoot the colorchecker in front of each painting I shoot? Those of you that use a colorchecker or similar what exactly is the workflow procedure and what does it do for you? I can definitely tell a difference between Adobe Standard and the custom profile (the custom profile seems to match the painting better).
Title: Re: Prints too dark but monitor calibrated
Post by: BradSmith on September 08, 2017, 09:59:52 pm

But, I have a question still about gray card use. It would seem that the gray card I was using has a higher reflectivity than the painting and therefore the exposure for the gray card was underexposed for the painting. So, since very few images have 18% reflectivity, what does a gray card actually do for you?

And another question about using the colorchecker. I created a colorchecker profile in the exact light I was shooting the painting in. If I shoot another painting of the same size such that I don't have to move camera or lights, can I use the same profile? Is there any reason to shoot the colorchecker in front of each painting I shoot? Those of you that use a colorchecker or similar what exactly is the workflow procedure and what does it do for you? I can definitely tell a difference between Adobe Standard and the custom profile (the custom profile seems to match the painting better).

Gray Card Proper Use - place a photographic gray card in the same light as your subject (painting).  Move in real close to the card so it fills your viewfinder, but be careful you or your camera aren't shading it.  Also be sure that you aren't getting bright, specular type light reflecting from it straight at your camera. (This may have been your problem with your use of the gray card)  Meter it.  That exposure should be very close to the "correct" exposure for the painting.  It would also be very close to a meter reading from an incident light meter placed at the painting and pointing back at your camera position. 

Color checker - The 2 most common uses for the color checker are: 1.  for developing a specific camera/light color profile.  You load this into your program (Lightroom) and then apply it to each image you import with this general lighting characteristic.  What it does is slightly tweak the color output for the colors from your camera sensor to try to bring them to a "standard".  In simple terms, it slightly changes some hue/saturation output in some colors.  In my experience, no brightness or exposure changes.   For my own use, I have prepared 3 Colorchecker profiles....sunlight, shade and tungsten lighting.   2. For setting white balance.  I fold the color checker open so the large, neutral light gray panel is seen.  Again, place it into your scene with your subject lighting and take a shot. Then remove it and take your final image as normal.  Back in lightroom, import both images, applying your color checker profile, then use the white balance tool in Develop Module on the gray panel.  This sets the white balance of the panel to what it should be, neutral R=G=B.  And this new white balance should then be applied to your final image.  The colors should now be very close to "real".

Hope this helps with your understanding of what this tool does.  Lots of good YouTube tutorials on it.
Title: Re: Prints too dark but monitor calibrated
Post by: BobShaw on September 08, 2017, 10:01:06 pm
Painting is 12inx12in, room is about 17ft square
Small painting, big room. Why 55mm? 120 would be fine and being macro gives you much better manual focus control

I took some more shots without using the gray card. I spot metered off several locations in the painting (the sky, the grass, the road,etc). Obviously, I got some very different readings at each location.
Exactly. This is why a camera meter is useless without a reference such as a grey card. Either that or you use an incident meter which measures the light arriving at the subject, not reflected off it.
I have aperature set at f/8, 100 ISO and I averaged the metering to where the brighter sky read 1/3 stop over exposed and the darker grass and road was 1/3 to 2/3 underexposed. I think the shot has much better exposure.
You are all over the shop. There is no place for "average"

But, I have a question still about gray card use. It would seem that the gray card I was using has a higher reflectivity than the painting and therefore the exposure for the gray card was underexposed for the painting. So, since very few images have 18% reflectivity, what does a gray card actually do for you?
No, it was correctly exposing the painting. If the artist wanted the painting bright then they would have used bright colours. The job in art reproduction is to reproduce, not improve. You don't change a Rembrandt into a Monet.

And another question about using the colorchecker. I created a colorchecker profile in the exact light I was shooting the painting in. If I shoot another painting of the same size such that I don't have to move camera or lights, can I use the same profile? Is there any reason to shoot the colorchecker in front of each painting I shoot? Those of you that use a colorchecker or similar what exactly is the workflow procedure and what does it do for you? I can definitely tell a difference between Adobe Standard and the custom profile (the custom profile seems to match the painting better).
No, if everything is exactly the same light and camera then once should be fine. Note that the colourcheckr can do the same as the grey card. You can set the exposure with the white. The colorcheckr is for colour accuracy. You need to fix the exposure in post anyway as the camera response is not the same as the eye. i.e., you need to make the whites white.
Title: Re: Prints too dark but monitor calibrated
Post by: Thenolands on September 08, 2017, 10:58:23 pm
Thanks BobShaw

I hear what you are saying about not trying to improve and only reproduce. The trouble is, the print is darker than the painting if I don't increase my exposure. Here is a pic of another painting (metered off gray card) and the print. I already have +20 brightness in Lightroom print module selected. Would you say it looks underexposed?

The histogram is way shifted left but obviously there are a lot of dark values in this painting so I assume this is as it should be.
Title: Re: Prints too dark but monitor calibrated
Post by: Thenolands on September 08, 2017, 11:17:28 pm
@bradsmith - thanks for your reply. I was using the spot meter on the camera and shooting the large gray card  in same light to get exposure settings  but did not zoom in to fill the frame as I am not using a zoom lens. Could this be throwing it off? I thought this was the point of a spot meter (so u didn't have to fill the frame) but maybe not.

Here is a shot of a different painting I did with metering off the painting itself. I'm actually like very much how well it matches to my eye (pic below- still slightly underexposed but much closer) but I also want to take the time to learn how to do it the "correct" way so that bugging me.
Title: Re: Prints too dark but monitor calibrated
Post by: BobShaw on September 09, 2017, 12:12:33 am
The trouble is, the print is darker than the painting if I don't increase my exposure. .... Would you say it looks underexposed?
It is way underexposed. That is why you should ignore the camera meter and start working with standard things. If you are not prepared to meter it properly then you need to just keep increasing the exposure until you get it right. See this image. The white needs to be white either by increasing the light or moving the exposure slide and noting the value.
Title: Re: Prints too dark but monitor calibrated
Post by: Thenolands on September 09, 2017, 12:28:40 am
Ignore camera meter or meter properly? You mean the camera meter is no good and I should be using incident meter instead? I feel like metering off a gray card with camera meter should not be this hard. Literally all I am doing is setting at f8, 100 ISO, and changing shutter speed until the spot meter in camera is directly in the middle, keep those settings, focus, take shot of painting. How is that wrong? 

I thought that increasing exposure in post created noise, no? The artist wants the ability to print these large so I prefer not to increase noise.
Title: Re: Prints too dark but monitor calibrated
Post by: BobShaw on September 09, 2017, 01:31:06 am
Sorry, but myself and others don't mind investing a bit a time to help beginners. However, let's recap.

You have a camera that costs the price of a small car.
You are not sure how to get the exposure right by any method.
You want to do art reproduction.

I suggest that you re-read the information in the last two pages.
If that doesn't clarify then I suggest that you do a basic photography course covering manual exposure and metering.
Then practise on a still life object like a fruit bowl.
You should advise the artist to get another photographer who specialises in art reproduction.
Good luck
Title: Re: Prints too dark but monitor calibrated
Post by: Thenolands on September 09, 2017, 02:07:24 am
I do appreciate your comments thus far but perhaps you could keep it on topic. I have a family member who is an artist who would like to be able to have some prints made - I am not some poser setting up an art repro shop ripping people off and giving you professionals a bad name or anything. I am a pharmacist by trade and am just trying to learn. I got the camera because I like the option of being able to print large and it is not a large portion of my income. Please feel free to not continue to post back if my skill level/camera cost combination doesn't suit you. All I am saying is the gray card is roughly 1+ stop underexposed compared to metering off the painting and the print seems to confirm that it does not match the original. I have filled frame with gray card and used spot from a greater distance and the metering is the same.

I would be more than happy to read or watch anything regarding exposure, and I have already read lots. The problem is, everything I have read is pretty simple and seems to be what I am doing.

I assume the large gray card in the passport is 18% and that is the value I should be using (I have read some things about 12% being more accurate which would help my case if so). I did purchase the camera used, it is not visibly damaged but how common/possible might it be the meter is broken somehow? Should I shoot the gray card only and look at histogram? It should spike dead center, no?
Title: Re: Prints too dark but monitor calibrated
Post by: BobShaw on September 09, 2017, 02:29:31 am
OK.
There is no large grey card in the passport. There is a very tiny one which is more suited to doing a white balance in post than anything else. A large grey card is 10x8" or so.
However the small one should work. if you are fill the frame with the grey card and set the camera so that the needle is in the middle, that should be correct exposure in manual mode. Ignore the painting reading.
I say should because you could have all sorts of other things set or the meter could be wrong.
And yes, there should be a bar in the middle of the histogram.

Doing that at ISO 100 and f8 indoors is going to be a long exposure. I am assuming that you don't have lights.

One of these will make your life a whole lot easier
https://www.bhphotovideo.com/c/product/1219217-REG/sekonic_401_307_l_308s_u_flashmate_light_meter.html
Title: Re: Prints too dark but monitor calibrated
Post by: Thenolands on September 09, 2017, 02:53:47 am
I have a pair of lights. Sorry, I meant large in relation to the tiny squares on the other side of the passport. In the first pic below, the side of the passport that is one color, that is 18% gray, right? I will take a pic/crop of just the gray card tomorrow and post the histogram.maybe that will get me somewhere.

I will keep that meter in mind. Thanks!
Title: Re: Prints too dark but monitor calibrated
Post by: farbschlurf on September 09, 2017, 03:42:49 am
Seems you didn't look up the link I gave, so here's the part important for you: (quote from link above from "fantasy photo", want to be correct to mention it's not my own writing!):

For photographers, the reflectivity of an "average" scene is between 12 and 13 percent. So, an 18% gray card would cause under exposure if used directly to set the exposure. But, by holding the card at a 45 degree angle to the camera, the reflectivity of the card would become about 12.7% since the reflectivity changes with the cosine of the angle (cos 45 is about 0.7 and 0.7 times 18 is 12.7). Or, just simple hold the card flat to the camera and then adjust the camera to over expose half a stop from what the reading from the card indicates.

I don't recommend the 45 degree "trick", myself, though, it's prone to failure when there are several lights.

If you have an incident-light meter, this would be the better option.

HTH

Title: Re: Prints too dark but monitor calibrated
Post by: Thenolands on September 09, 2017, 03:50:28 am
No, did read it. I just hadn't read the 45 angle anywhere else but I think I determined the problem. As BobShaw I think was trying to get through to me, that card is not 18% gray! I think 18% gray is much darker. If I am not mistaken, by metering off a lighter card, the camera wants to make it darker so underexposes. I just saw that larger gray card and thought it must be an 18% gray. I will remember the 45 angle for smaller tweaks if I need it, though
Title: Re: Prints too dark but monitor calibrated
Post by: BobShaw on September 09, 2017, 06:18:06 am
I have a pair of lights.
That is a whole new world that you have just shared with us.
What sort of lights?
Title: Re: Prints too dark but monitor calibrated
Post by: nirpat89 on September 09, 2017, 07:55:54 am
I thought that increasing exposure in post created noise, no? The artist wants the ability to print these large so I prefer not to increase noise.
The answer is No.  Not to any appreciable degree.  Perhaps important if are trying to resolve high-frequency lines on a lens chart.  Not of any consequence to enlargement of an oil painting where the brush strokes will be bigger than the any noise you might introduce with the 645z and 100 ISO.  I think this belief is making thing more complicated for you than it needs to be.

There is no mandate to get the exposure right in the camera.  Only thing you have worry about is there is no clipping of tones in the left side of the histogram, which you do not seem to be doing based on what you shared in your first set of images.  Simply put it in Lightroom and move the histogram to right with whatever knob you want to turn until you get the correct light level.  Print small patches along the way to fine tune. 

If you still want to get is right in the camera, as I said before, set aside your Passport (more trouble than it is worth.)  Use your camera exposure meter in the average mode (not spot mode) take a shot based on that.  Assuming that you are going to underexpose this way for whatever reason, take several more shots reducing the shutter speeds at 1/2 (or a 1/3) stop intervals, until you see the histogram in your camera starts showing clipping on the right side.  I do not know how auto-bracketing works in Pentax, but you can do this without having to manually change the shutter speed.  Now open the shots all in Lightroom and pick the best one. 
Title: Re: Prints too dark but monitor calibrated
Post by: Thenolands on September 09, 2017, 09:26:04 am
Quote
Quote from: Thenolands on Today at 02:53:47 AM
I have a pair of lights.
That is a whole new world that you have just shared with us.
What sort of lights?

They are not expensive or anything but they seem to be providing even light light coverage...
https://www.bhphotovideo.com/c/product/1008971-REG/impact_ready_cool_2_lighting.html

Thanks for the noise clarification. I don't want to go around shooting 1 stop under all the time but it IS nice to know I can process in post without worrying. Thanks!
Title: Re: Prints too dark but monitor calibrated
Post by: Thenolands on September 09, 2017, 01:27:23 pm
Got gray card (an actual 8x10 18% gray card) and metering is now showing 1/6 second instead of 1/30... that ought to do it!

Thanks for everyone's help. Much appreciated!
Title: Re: Prints too dark but monitor calibrated
Post by: Christopher Sanderson on September 09, 2017, 02:04:54 pm
The paintings are quite lovely. Don't forget to use your eyes as the best and final judge of the print.

For instance the photo of the sunflowers/blue vase appears quite good but possibly about a stop darker than the original.

Again the use of the Lab readout values on that JPG would inform you of the realtive accuracy of the tones.
The highlight in the plate of your print reads L 83.7, the canvas reads L 93.7 in the same area - that is a 10% difference in Luminance at the top end making your print less bright in the highlights.
The midtones at the centre of the vase read L 46 on the print and L 57 on the canvas. Again the midtone of the print is considerably darker
BUT
The darkest area of the vase on the left reads 18.6 on the print and L 21.0 on the canvas. Only slightly darker in your print
This suggests that the print has 'crushed' the mid to top end a bit but is only very slightly dark at the bottom end.

Please don't interpret these numbers as anything more than a rough guide to what is going on in your print. But it is a lot easier to compare numbers than tonal values by eye on different textured surfaces where at a minimum, reflections can throw things way out.

The 'correct' method is the one that gives you the best result and that will at some stage require your eyes to make the judgment. Lab readout will give a guide but technology does not trump your eyes IMO
Title: Re: Prints too dark but monitor calibrated
Post by: Thenolands on September 09, 2017, 02:25:11 pm
Yes, Chris, I agree it is slightly dark. That shot was also before use of the gray card. I am reshooting that painting now, in fact, and it did show to decrease shutter speed from 1/8 to 1/6 using gray card vs metering off print so I think that would take care of most of the slight under exposure. Good tip, though, about your eyes being the final check. It is how we are actually viewing the piece, after all.
Title: Re: Prints too dark but monitor calibrated
Post by: BobShaw on September 11, 2017, 05:50:56 pm
Got gray card (an actual 8x10 18% gray card) and metering is now showing 1/6 second instead of 1/30... that ought to do it!
It certainly should. That is over 2 stops from the previous method.
How much quicker was it to actually correctly measure it rather than experiment?
If you stood ten people in a row and asked them to compare the brightness and colour of two objects then you would get 20 answers. The human eye is notoriously variable. It depends on the person, the time of day, how they are feeling etc. There is a famous post where people were asked the colour of a dress, blue or green with varying results. Subjectivity has no place in art reproduction. Fortunately a technical approach will always work.

If you go from correctly exposed with correct camera calibration and scene calibration through to correct print calibration then it should be right.
At least if it isn't then you have a process that you can go back and review and find out where you went wrong or introduce a controlled subjectivity. You have a repeatable process.

The one thing which is completely out of the equation and which everyone spends so much time on is monitor calibration. If the numbers are right then you can ignore the screen. It is not in the path. Cheers.
Title: Re: Prints too dark but monitor calibrated
Post by: Thenolands on September 11, 2017, 06:36:51 pm
Well said. Do you have any recommended reading on use of histogram to verify the accuracy of exposure? For example, lets say you had an overall dark toned image, you would expect histogram to be shifted left of center but is there a way to tell if it is also underexposed?

I ask because my family member texted me and said they look good but she had a few that she said "needed tweaking" ... well, what she did was either notch the exposure down or deepen the blacks (not sure which) to something that suited her eye (she is not very technical so she is not basing this on histogram, etc.). So basically the artist is taking a reproduction of her own work and creating another work by changing it! Ugh.  I explained that her monitor was probably too bright, for one thing. But is there a way I can show her technically speaking that these are not "too light"... can you imagine she is darkening these reproductions after all this?! Can't believe it!
Title: Re: Prints too dark but monitor calibrated
Post by: BobShaw on September 11, 2017, 07:46:39 pm
Go back to page 1 of this and watch the video from Andrew Rodney. Everything you ever wanted to know about histograms and more.
In a nut shell, i only use the histogram out in the field. In the studio if there is any doubt about exposure I measure it with the incident meter and never look at histograms.
The reason I asked about your lights was in case you were using flash, in which case shutter speed would have no effect.
Your lights are quite weak to need that long a shutter. You then risk ambient light affecting your exposure as well. You would need to turn off the room lights and draw curtains.

There is not much you can do about someone else's monitor. You will need to work from a print or show it on your screen.
Title: Re: Prints too dark but monitor calibrated
Post by: digitaldog on September 11, 2017, 07:53:13 pm
In the studio if there is any doubt about exposure I measure it with the incident meter and never look at histograms.
Which Histogram? A raw one is kind of useful. RawDigger, worth it's weight in exposure gold.