MACRO PHOTO: The classical definition is that the subject projected on the “film plane” or digital sensor is approximately the same size as the subject. Recently, it has been used in advertising as a camera that is able to focus on a subject so that when a 4×6″ print is made, the subject fills the print (or larger).  I have decided that using the term “close-up” doesn’t have to explain itself like the term “macro” does. In either case, it is photography that captures more detail than we are normally used to seeing with our eyes without the aid of an optical device. Generally, the two terms are somewhat interchangeable; however, purists will go on and on about the differences between them.  Semantics have always been a moot point.

Someone recently asked about extension tubes and I created a brief entry on the subject. I also wrote an article relating to DSLR exposure modes.  Displayed below are image comparisons of shots made with macro lenses and extension tubes.  I used a Nikon 50mm f/1.8 lens with the extension tubes  for simplicity’s sake.  I also took several shots using Nikon 105mm and 60mm prime lenses. The idea is to give an idea of the differences by using visual comparisons.  Although this project was not an extremely controlled setup, the criteria was to get as close as I could to the subject, in this case, playing cards, and focus on them. I used several different f-stops and their related shutter speeds.  The extension tubes render the aperture adjustment useless. So when taking closeup shots using the extension tubes, the only critical factors are shutter speed and focus.  The shots will be explained as you scroll down the screen; however, I started with the 105mm micro lens, attached all of the extension tubes with the 50mm lens, and finally, several shots using the 60mm macro lens with various aperture openings.

This shot above shows that at an aperture opening of F/9, the top half of the image is out of focus. Using a smaller aperture like f/22 would make more of the image in focus.

As you can see in this image, stacking all of the extension tubes really gets you close to your subject. Even with good lighting (daylight corrected fluorescent), the exposure time is rather long at 1/4 of a second. A tripod and remote shutter release is necessary to remove as much movement as possible.  In addition, you have to be careful to not move the camera/tripod as the focus point can be lost with only a fraction of inch of movement.

In this project, I connected a laptop to the D70 via USB and was running Nikon Camera Control software. This allows changing settings without touching the camera.  In addition, I have the camera powered with an AC/Adapter charger (EH-5) which allows me to forget about battery charge life during the session.

Extension tubes have no optics. They merely create distance between the camera’s sensor and the lens. The further the lens is from the camera’s sensor, the more the lens is forced to focus much closer to the subject. Since the distance is increased as more of the tubes are added, the exposure time has to be increased to compensate for this added length.

The next image is a crop of the full sized image with no reduction.  Obviously, all the other images have been reduced for browser display.

The image above was made the same as the last; however, the 36m extension tube was taken off the stack and the shutter speed was increased to 1/5 of a second.

The above image was taken with the 12mm extension tube coupled with the 50mm lens. This is the last shot using the extension tubes. Note that the depth of field is not as critical when the subject is shot head-on. This changes when shooting at an angle and across the plane.

The photo above compared to the one below show the effects of aperture size variations. The image point of focus was at the top of the card. In the photo above the aperture is set to f/9 and the foreground is out-of-focus. The 50mm lens is consider the lens that is closest to what the human eye sees.

The image above has the same setup as the previous image, but the aperture size was set to f/22 giving a greater depth of field. Noticed that the foreground is now in focus as well as the top portion of the photo.

The Nikon 60mm  macro (Nikon calls it Micro) lens creates tack sharp images. This image was taken at the closest focus point that I could manage to give an idea of what a photo looks like when you move the camera and lens in as close to the subject as possible. The following images were taken at an angle to emphasize the effects of varying the aperture size - f-stop.

This photo is relatively sharp across the plane. You can see a blurring effect moving up toward the top of the image. The following images will show how the depth of field decreases as the aperture opening increases.

Notice in this final image that the depth of field is so narrow at f/8 that the queen’s nose and mouth are all that are in focus.

Depth of field will allow you to emphasize specific areas in your photograph while making others nearly indistinguishable.

As you can tell from the images, it takes a lot of setup time as well as trial and error to get good images using extension tubes.  Good macro lenses are much easier to use when making close-ups.  However, they are much more expensive.

The 105mm macro lens is very useful for taking photos of skittish things like insects. It also works will as a portrait lens. The 105mm macro lens can focus as close as 1 foot from the subject.  The 60mm focuses as close as 1 7/8″ from the subject for 1:1 (meaning the subject is the same size on the photo sensor as it is in real life. Generally speaking, the shorter the focal length, the less expensive the lens.

The Nikon 60mm and the 105mm lenses are prime lenses. This means that they are a fixed focal length and will not “zoom”.  They are also “fast lenses“.  The speed of a lens is in reference to the maximum size of the opening of the iris in a lens or the minimum “f” number.   Both the 60mm and the 105mm Nikon micro lenses are considered fast lenses as they can open up to f/2.8.  The Nikon 50mm f/1.8 is an even faster lens.

Technorati Tags: macro, micro, closeup, close-up, nikon, lenses, extension tubes, aperture, shutter speed, exposure

Here are a few points on small venue concert photography.  Here is the gear that I used:

• Nikon D70 w/50mm f/1.8 Nikon lens
• Nikon D80 w/70-200mm f/2.0 lens
• Domke F-2 camera bag (olive)
• Charged batteries in camera, extra in bag
• Extra memory cards (unless you have a large one - obviously we all have various gear and budgets)

Camera settings:

• 1600 ISO
• 1/60th second  - f/8 - set your camera to manual you can move the speed/aperture up and down as needed
• Single spot exposure setting - don’t use matrix it will throw things off
• Auto-focus on continuous - because the band is on the move

NOTES:

• Get close and move around
• Take lots of photos - many do not turn out and you don’t have time to check them on site

• Switch between the two camera/lenses
• Stay on the band and continue to look at them through the viewfinder
  • Look for group interaction
  • Look for expressions
  • Wait for exciting “build-ups” and then take the shots
• The reason that I mentioned the bag was because it does not raise any attention to itself. The shoulder strap allows you to sling it onver your shoulder and do whatever you need to do. The flap can be clipped op at will to allow you to easily switch cameras.

In my case in this shoot, the lights did not vary a great deal. The lighting stayed low and there were few times the band was well lit. I had to wait for the occasional times when the lights “were up”. In my case this was rare.

Post Processing:

• Backup everything to disc right off the bat
•  Mark all of your shots with stars (I use Adobe Bridge).
• Select all of the 3-4 stars or more shots
• You’ll most probably need to run filters to reduce the noise
  • Noise -> Reduce Noise
  • I set my strength at 10, reduce color noise 100%, sharpen details 15%, and set the preserve details based on the image

These are not hard rules, just the ones that I used; however, you WILL need to reduce the noise level.  I do not own Noise Ninja, and you may have this filter/software. I have heard it works very well.  Since these images will end up online, it is not that critical.  Should you make prints, you’ll have to take extra special care as the noise will be much more apparent at full size.

On a final note, using a flash unit won’t work very well in this setting. First of all, if you take a lot of shots, which you should, the flash will drive everyone (in and out of the band) crazy and you will be irritating. Secondly, flash lit shots don’t give the look that you want, which is a natural, “what you really see” look to the images.

Technorati Tags: concert, photography, photos, small venue, music, night, images, imagery, photoshop, reduce noise

 
Before and After (click for larger image)

An easy and very effective way to convert to black and white in PhotShop is to use the channel mixer: 

1. Create a new adjustment layer:  Layer > New Admustment Layer > Channel Mixer

2. Click on Monochrome

3. Use the sliders on each color channel to adjust your image

4. When you have it where you want it, flatten the layers and save

1. Image>Adjustments>Auto Levels
   You could do the levels manually if you want; however, auto seems to work well for this adjustment.
2. Duplicate your layer
3. Image>Adjustments>Equalize
   This adjust the brightest pixels in your image to white. The darkest pixels will go black. After this command is executed, check the histogram. It will appear level almost all the way across
4. Set the equalized layer’s blending mode to Soft Light
   The image should look less harsh and have a better contrast
5. Drop the Soft Light layer’s opacity
   Try dropping it to 30-35%. However, try different opacities to adjust it to what you want in the image.
6. Merge the layers

Technorati Tags: photoshop, filters, photography, digital, image, contrast, post processing, photo, tutorial, tips, techniques

• Get to the location early - If you haven’t already scouted the wedding location, the dressing and the reception areas, this is a must. Coming in cold a short while before the ceremony is a recipe for disaster.
• Get to know the wedding party as much as you can beforehand - The more your know the wedding party, the more at ease they will be with you and the closer and more comfortable you’ll be with them. Great photos will have a lot to do with how at ease they are with you. It’s nice to be called by your name, instead of “the photographer”.
• You are the photographer - Don’t forget this important fact. Your job is paramount. The ceremony and the reception is for the moment, the images you provide may have to last for more than a lifetime. You are not only creating nice “works of art” for the bride, you are also documenting history for the family. Do your dead level best job at carrying out this important project. You don’t have to be pushy or bossy. Everyone already knows that your job is critical and they want you to succeed.  Your aittitude and demeanor has a directr impact on the subjects of your photos. 
• You must have a flash - Churches can be well lighted and churches can be almost dark. Most of them are relatively dark.  You need a flash and it should be off-camera. 
• You need a powerful flash with a great refresh rate - The majority of church sanctuaries are large. This necessitates a powerful flash. Shooting in RAW may allow you to increase the exposure. However, there is a point of diminishing returns where noise creeps into the image and lots of it. Increasing the ISO helps some; however, the noise factor again becomes apparent.  The refresh rate of the flash has a large bearing on whether you get all of the shots you want or one of the shots that you want. It is difficult to get the exact one you want unless you have lightning reflexes and that is not always as easy as it sounds.
• A tripod is nice and even necessary, but don’t depend on it as a way to overcome darkness in a dimly lit church - Several factors work against the use of a tripod to take sharp shots. Young children are constantly on the move. People blink, move their hands, etc.  A flash and a tripod make a good combination.
• Take plenty of the same posed shot of groups - Eyes close, hands raise to swipe hair or scratch an itch. People are distracted. Make sure you get their attention once you have them in position for the shot. Taking these extra shots of the same pose will increase the odds of having one very good shot of the group. The larger the group, the greater the odds that something will be out of kilter.
• Pay attention to details - Half open zippers, flipped collars, hair out of place, and a thousand other little details can detract from the finished photo. Take the time to notice each individual.  Learn about posing and balance the group. Turn some people, have some stand on the next highest step, and so on. As you pose them, look for that special balance that is needed for a pleasing picture.
• Look for the emotional outbreaks (the good kind) - they only last a few seconds - A hug, a smile, a kiss, a pat on the back can all add human interest to an otherwise hum-drum image. Engage your subjects. Use humor to get them going, even being a little silly can get them rolling. After all, most of the time, your subjects are nervous, tense, or stiff.  They are so absorbed in the moment that they are having difficulty relaxing. A relaxed person makes a much better subject than a stiff or nervous one. I use things like “You’re all movie stars…smiles all around” (and I wave my hand like and Italian chef) or “OK…more fake grins everybody, act like you really care about all of this” (and then I look up and cross my eyes at them or make a funny face).  Anything that is somewhat goofy seems to lighten up an otherwise self-conscious group. Tell them how wonderful they look and the smiles will surface.  Don’t forget that these are people too and they like and dislike many of the same things that you do.

• Keep a mental list of locations that you can use for candid shots  - This comes in  handy once the groom and the bride are available for those special shots of just the two of them.  Find out all you can about how the ceremony is going to process and proceed. This is vital as you have to be where the action is. If you are using limited flash power, find out ahead of time where the subject need to be in the center aisle before you shoot. Also, if your flash has to take a second or two to refresh, make sure you get an idea on timing your shots. You may only get one or two shots of each group that processes down the aisle. You might even start a “clip” book or folder that contains photos that you particularly like. You can attempt to use the same style or even embellish it with your own version to create interesting images. Remember, there is nothing new under the sun. Most of the fantastic photo that you see today were inspired by other great photos.

• Ignore anyone taking snapshots and/or video - Again, you are the photographer.  If someone is holding a video camera and you attempt to avoud their line of sight, your will lose some of your flexibility when it comes to moving around the altar area. - I strongly suggest that you stay on the groom’s side of the  sanctuary so the lion’s share of shots are of the bride. If you are on the groom’s side you will have the bride’s face in view. After all, she is the one that wants the pictures. You can always move over and get shots of the groom. The bride comes first.

• Don’t be afraid to move into the middle of the aisle at important portions of the ceremony to get a shot of both the bride and groom in a more centered, symetrical shot. Even though many of your shots will be from one side of the altar or the other, you still need some of those head on altar shots.

• You’ll need to move in as close as you can when the ring exchange occurs - The suggested minimum distance from the couple is ten feet. Even that may seem a bit close. However, if you want to actually get the rings in a photo, you’ll need to move in fairly close.

• Keep a loose eye on the family members during the ceremony - At important points along the ceremony many of the family members will beam and maybe even tear up during these times. When the minister pronounces the bride and groom as man and wife, when they are called Mr. and Mrs., and so on, these are the times when the family lights up with emotion. It may be big smiles, it may be tears. Regardless of what the emotion brings, it is usually a great shot for you to capture. Don’t forget kids the whole time, they seem to be doing all kinds of funny things that you can get shots of.

Using the following steps you can make a photo image look older:

1. Open your image in Photoshop

2. Desaturate the image: Image -> Adustments -> Desaturate

3. Make the image a duotone: Image -> Adjustments -> Variations (select the tone you like)

4. Create a new layer.

5. Select a foreground color from a mid-tone color your now variated image and make the background color white

6. Select Filter -> Render -> Clouds

7. Select Filter -> Blur -> Motion Blur  (Make the angle 90 degrees and the distance Max to the right)

8. Now set that layer to hard light

9. At this point you may optionally make this layer more transparent

10. Flatten the image

11. Create a new layer

12. Set your foreground color to white

13. Select a Paper Damage Brush (you can download if you don’t have them ready to load)

14. Stamp the image with the brush. If the image is larger than the brush, use the Move, hold down the shift key and resize the it so that it covers the entire image.

15. Make the layer as opaque as is effective

16. Flatten the image

One thing that you can optionally do is use the eraser on the paper damage brush impression layer to take away any “damage” that may hinder the details on your image. 

Here is the original image that I used:

Technorati Tags: photoshop technique tips tutorial old age aging image photo portrait digital editing alteration

There are various ways to touch up skin in Photoshop. Some seem more adept at specific areas of the face than others. I have tried various filters to show these various effects. I found that some of the filters do a much better job than others. Younger skin is much easier to touch up than skin that has weathered the years. The subject in my example image is a middle-aged female. Most ladies at this age want to have their skin look like it is 20 years old. That is a big order, but getting close to it is the challenge that may be met using a combination of the following filters with layers and the eraser tool.

Original image of portion of the face unretouched

The original image shows signs of natural aging. The pores are very visible. There are wrinkles around the mouth and below the eyes. In a senior person, wrinkles can be dimished, but should not be completely taken away. Should the wrinkles be completely taken away, the image does not look realistic at all. So, smoothing the areas where pores show can be done. The wrinkles can be diminished but not taken away entirely.

Skin Surface Blur Filter Applied
with a Radius of 36 pixels
and a Threshold of 32 Levels

The Skin Surface Blur Filter seems to smooth out skin pores very well; however, the shadows areas around the nose begin to pixelate and look unrealistic. When using the Surface Blur Filter, it is important to note that the radius controls the blur intensity while the threshold controls the sharpness. This filter can be appled and used with the following steps:

1. Duplicate the background layer

2. Make the duplicate layer invisible

3. Select the background layer

4. Filter -> BLur -> Surface Blur (change the Radius and Levels to suit your image skin requirements)

5. Make the duplicate layer visible

6. Select the duplicate layer

7. Set the eraser tool to about 30-35%

8. Begin erasing the porous areas of the skin until the desired smoothing is achieved

9. Merge the layers

Reduce Noise Filter Applied to Original Image 3 Times

The Reduce Noise Filter seems to work very well at preserving facial details. In this image example, the area around the nose has been nicely smoothed while the detail has not be overly diminished. Here are the steps that achieved this result when applied to the original image:

1. Create a duplicate layer from the background

2. Make the layer invisible

3. Select the background layer

4. Filter -> Noise -> Reduce Noise

5. Settings for this example: Strength=10, Preserve Details 0%, Reduce Color Noise 0%, Sharpen Details 0% 

6. Run the filter 3 times total for the effect

Noise Median Filter with a Radius of 8 pixels

The Median Noise Filter also works well for retouching the skin. If the eraser tool has the opacity set very low, this filter can work very well on all areas of the skin. However, this filter has to be used carefully as the final image may look too much like a cartoon with many important details getting lost in the smoothing.

My first attempt at re-touching skin in portraits was using the gaussian blur filter. I found that using the Gaussian blur filter works but it loses a lot of detail much too quickly. In addition, if the radius is set low enough to preserve important details, the skin does not get smoothed enough for the results that I am attempting to get. Here is the original image with the Gaussian Blur applied with a radius of 7:

Gaussian Blur Filter Applied to Original Image
with a Radius of 7

The great strength of Photoshop is using layers. Time is always of the essence, so choosing the most time/cost effective way to touch-up photos is key. Use the comparisons above to make your own decision on which filter works best for you. Using several of these filters with layers, erasing the “rough spots” will help make a very nice image. Since no single filter seems to do it all, using several of the filters on duplicate layers of the background/original layer may make a big difference in how you post process your portraits. Here is the “final mix” image:

The “final mix” image is a a combination of
the Median Noise Filter and the Surface Blur Filter

Technorati Tags: portrait photoshop filters touchup touch-up touch up skin tutorial tips techniques photo editing post processing

Original Image

1. Open your portrait image in Photoshop and create a duplicate layer

2. Select the duplicate layer

3. Use the eye dropper to select a portion of the color surrounding the highlight and set your small brush to about 30% transparency

4. Begin covering up the highlights within the eye by working small areas and going over. The highlights will begin disappear. You may have to select color areas in severl steps depending on the image

5. Once the highlights are covered, select the dodge tool (which lightens the image) and set opacity to about 30%

6. Make the dodge tool small enough to fit within the whites of the eyes and begin working the whites.

7. Make the lower portion of the eyes lighter than the upper portion and make sure that you lighten close the the edges of the iris

8. Once you are happy with the work you have done, merge the layers

Image with highlights covered and whites whitened (Steps 1-9 above)

1. Create a new layer - name it Highlight - Select it

2. Set a soft brush to white with opacity to 65%

3. Set the size of the brush to the size that you want the new highlight

4. Give the area of the iris where the natural light would fall a shot of white (shown below)

5. If the highlight is not bright enough for you hit it again

6. Do this for both eyes with the eye facing the light having more highlight

Image with new highlight (Steps 1-6 above)

1. Make sure you have the Highlight layer that you just put highlights into selected

2. Make the layer a layer mask by selecting the icon at the bottom of the layer panel

3. Make your colors default - black foreground, white background

4. Set a small soft brush to 30% opacity and begin to erase the highlight, especially in the pupil area

5. Continue until you are satisfied - You can change the color to white to undo some of your erasing

6. Merge all all layers

Image after cleaning up added highlight (Steps 1-6 above)

1. Create a new layer called Color Highlights

2. Select a color from the pupil, open the color selection box and select a color less muted

3. Select a soft brush that approximates the color portion of the iris and apply the color

4. Don’t worry about coloring areas that you don’t want color on - apply liberally

Image with color highlight applied to Color Highlight Layer (Steps 1-4 above)

1. Select the Color Highlight layer and make it a Layer Mask by selecting the icon at the bottom of the layers window

2. Make sure the default colors of balck foreground and white background are selected

3. Use a small soft brush at 30% opacity and use the black color to erase the portions of the highlight color

4. Do this until you begin the see the detail of pupil color variations begining to show

5. Erase all color from the outer edge of the iris, the pupil and the whites of the eyes

6. Merge all layers and you should have the eye work completed

The final image

Obviously, the more care and time you put into these steps, the better the final image will look. I honestly rushed through the steps for this blog entry. Critically speaking, I think that the white specular highlight should have a more crisp look to the right edge of the eye and I was sloppy adding the color highlight as well. However, using care and these steps will give you a very artisitc interpretation while maintaining the actual look from the original photo.

After going back to the image, I did one more step on the eye that is highly optional. I used the dodge tool to make the color highlight area more transparent and lighter. The image is displayed above. I like the effect. 

In addition, the skin needs to be smoothed to compliment the eye work. I have a tutorial which shows you step-by-step how to do this:

Skin Smoothing Tutorial

Technorati Tags: photoshop eyes portrait toughup tough up face post processing airbrushing technique tips tutorial

I have experimented with various techniques for touching up photo portraits. Simplicity is always key. It it saves time, it is easier to recall, and easier to execute. The important consideration is that the simplicity brings excellent results. Many touch-up techniques use the Gaussian blur to achieve the results of smooth skin; however, I honestly believe that the Filter -> Noise -> Median function actually works best. It leaves the edges of the image more intact which is vital to the realism of the original image.

The skin smoothing is only one aspect of the total work to be done. So, I will start at the beginning of a touch-up session:

1. Optionally, use the Healing Brush Tool to take care of any pimples, bumps, scars or other minor skin imperfections. These are usually color abnormalities. Don’t spend too much time on this. The next steps will clarify the skin a great deal as you will see. This particular image had no imperfections that needed this step.
2. Next create a duplicate layer
3. Click on the eye icon on this layer to make it invisible
4. Now click on the original background layer to make it active
5. Goto Filters -> Noise -> Median
6. Move the slider bar (you’ll have a preview) until the skin is smooth like you want it. Don’t worry too much if it is very blurred, just make sure it is smooth enough for your liking.
7. Click on the duplicate layer copy (top layer) and click on the eye icon once again to make it visible
8. You should have the original image you opened showing.
9. Set the Eraser Tool to about 40-50% You may have to move your maouse or pen over the areas several times to increase the smoothness. With more mature people, you may want to leave some slight impressions of any wrinkles. Removing them completely tends to take away the true character of the person and leaves them looking unrealistic. Experiment with the skin on the face to see what best results you can derive.
10. Begin erasing areas of the skin which will make those areas smooth. Adjust the size and opacity to suit your needs. Some areas will need more help than others.
11. Once the skin areas are smooth like you want them, flatten the image.
12. You should have only one layer now and it should be ready for the final touches.
13. For the eyes and teeth, you can use the Dodge Tool (this lightens the areas you pass over)
14. Set the opacity to about 25% and change the size of the tool to easily fit into the whites of the eyes
15. Begin stroking over the redness and other discolorations of the whites of the eyes they will begin to lighten (I used it on the right part of the left eye above as you can notice the difference between the before/after image above)
16. Do the same for the teeth - make the size of the tool is about the width of the tooth you are lightening - even strokes up and down seem to work best.
17. One of the last things that I do is work on the eye color a bit since they are usually the focal point of the photo.
18. Lasso the eye(s) and optionally increase the saturation a bit. Be careful not to overdo it
19. Another optional step (while both eyes are still lassoed) is to Filter -> Sharpen -> Smart Sharpen - Again, don’t overdo this; however, this shrapening step can often make those eyes really snap!
20. The only other thing that you may want to do is to use the blur tool to even up any areas that seem a bit posterized. If you have Corel Painter, you can use the soft blenders to even things up as well. Sometimes, the Filter -> Noise -> Median function will have a posterization effect where the skin shades are not graduated in a natural manner.
21. Save your file.

Technorati Tags: photoshop, portrait, skin, touchup, touch-up, portrait, finishing, post, processing, face, facial, digital, editing, edit, airbrush, tips, techniques

Before

After

Here are steps to create the after version shown above:

1. Duplicate the image (optional)

2. Convert image mode to lab color

3. Select the lightness channel

4. Convert image to grayscale mode (discarding the other channels)

5. Convert the image to duotone mode

6. Select the color tone you want (or OK for the default as in this example)

7. Convert image to RGB mode

8. Duplicate the current layer

9. Select that duplicate layer

10. Filter > Blur - Gaussian Blur (20 pixels)

11. Set current layer’s blend mode to multiply

12. Flatten image

13. Duplicate the current layer

14. Select the duplicate layer

15. Set the blend mode to screen

16. Flatten the image

17. Duplicate the current layer

18. Desaturate the duplicate layer

19. Invert the layer

20. Filter > Blur > Gaussian blur (3 pixels)

21. Set the layer’s blend mode to soft light

22. Set the layers opacity to 50%

23. Merge visible layers

24. Dulicate current layer

25. Set the blend mode to screen

26. Filter > Sharpen > Unsharp Mask (Amount 20%, Radious 50 pixels, Threshold 0)

27. Flatten Image

 That is it. As you work through the steps, there will be times in the process where you might not think that your image will end up the way you want it; however, once all of the steps are completed, you will get results similar to the after image shown above.

Technorati Tags: photoshop, tutorial, tips, techniques, image, editing, portrait, soften, duotone, skin, face, headshot