Howare neutral density filtersmade

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Budding portrait photographer who want to maintain a wide aperture on fast lens during bright days should start with a three-stop ND filter. If you’re a videographer, a variable ND makes the most sense.

Quadrilateral filters are used with specialized adapters/holders. They are often more cumbersome to carry than circular filters, but also offer more variety and versatility. For example, there are adapters available that will allow you to attach these filters to lenses with bulbous front elements where circular filters would be impossible to place.

What are neutral density filtersused for

Very strong (16 stops or more) neutral density filters should be used to photograph the sun and solar eclipses. In addition, you should never view the sun through an optical viewfinder — even with strong ND filters in place. While ND filters inhibit visible light, most do nothing to stop harmful IR and UV radiation from damaging your eyes.  You should always use live view or an electronic viewfinder. It’s also recommended that you place the ND filter on your lens before pointing it at the sun with a large magnification lens because the concentrated light may damage the camera’s image sensor.

One of the most popular uses for an ND filter is to deliberately increase exposure time. You can “smear” the appearance of clouds and make flowing water look silky smooth. It has the effect of smoothing out moving textures. Another interesting use of a strong ND filter is to “get rid of” moving objects like people and traffic from a scene. If an object is in motion and a strong ND filter is used, the object doesn’t occupy a particular space long enough to give off the requisite amount of light to be captured by a camera. Try this in a mall or street corner and you’ll be amazed by the results. Remember, you’ll need an ND filter strong enough to prolong the exposure to at least four minutes.

For example, a one-stop ND filter would let in ½ as much light. A two-stop ND filter would let in ¼ the amount compared to no filter and ½ as much compared to a one-stop ND filter. Thinking of it temporally, if the exposure time without a filter is one second, then one-stop ND filter would prolong that time to two seconds. A two-stop ND filter would prolong it to four seconds. A three-stop ND filter would prolong it to 8 seconds, and so on.  The chart below offers other examples to illustrate this concept.

This study had several limitations. First, we included only a small number of patients. Second, this was not a randomized controlled study and we did not directly compare the long-pulsed Nd:YAG laser with PDL and IPL. Third, long-term follow-up was not performed.

The strength of a neutral density filter refers to its ability to hinder light. This is measured in stops. Each whole number increase in stop inhibits 50% of the light.

Five men and nine women were finally enrolled (mean age 45.4 ± 16.4 years) in this study. Thirteen of 14 patients (92.9%) had good or excellent PGA results. Ten of 14 patients were very satisfied or satisfied with the clinical results (71.4%), and all patients reported that immediate treatment discomfort was tolerable. Side effects were minimal; four patients (28.6%) reported erythema, vesicles, or hyperpigmentation which recovered without scarring.

With regard to side-effects, higher risk of potential collateral damage around vessels and pain during the procedure should be kept in mind when using this laser for vessels.2 Water, a competing chromophore of light at the wavelength of 1064 nm, may be the culprit responsible for additional tissue damage despite the fact that this wavelength is absorbed 10-fold more by oxyhemoglobin than water.2 In our study, all patients tolerated the procedure moderately well without remarkable pain. Two patients experienced postinflammatory hyperpigmentation on the site of the vesicles; this epidermal damage may have been caused by the high fluence. Technically, a non-overlapping technique is very important to avoid subsequent complications like scar formation.15 When we performed laser therapy to treat telangiectatic vessels, we evaluated the therapeutic end point based on the immediate response of the vessels. However, when treating diffuse erythema rather than telangiectasia, clinicians should be cautious when selecting parameters; however, guidelines to reduce adverse reactions have yet to be established.

Among the lasers for vascular lesions, the ratio of melanin to blood absorption is similar at 585 and 1064 nm, whereas the absolute values of absorption and scattering coefficients are considerably lower at 1064 nm as compared with 585 nm.7,8 It might imply that 1064 nm pulses can treat deeper vessels selectively. Lower absolute values of blood absorption at 1064 nm can be compensated for by increasing the fluence. Although a very high fluence of more than 150 J/cm2 must be applied, this increase in treatment fluence does not necessarily damage the epidermis, because the absolute absorption of melanin is lower at 1064 nm as well.4 In addition, the absorption coefficient of blood at 1064 nm is 0.4/mm, which is much higher than that of the surrounding dermis (0.05/mm) at the same wavelength. This difference in absorption coefficients makes 1064 nm light more selective for treatment of deep blood vessels than shorter wavelengths of light.8,9

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A 1064 nm long-pulsed neodymium:yttrium-aluminum-garnet (Nd:YAG) laser has been proven to be effective for the treatment of leg veins because of its deep penetration into the skin and homogenous heating of large vessel walls.2 Recently, the efficacy of long-pulsed Nd:YAG laser treatment for various vascular disorders such as port wine stain, hemangioma, angiokeratoma, and venous lake was reported.5,6

Neutral densityfilter chart

The vast majority of GND filters are rectangular in shape. They are darkest at the top and gradually become clear near the midpoint of the filter. The strength of the GND filter is determined by its darkest portion.

Variable ND Filter

For example, a three-stop GND filter only inhibits three stops of light at the very top (darkest part) of the filter.  As we travel down the filter, there is a gradual transition to 0 stops (clear). It is used during late afternoon or early morning when the sky is much brighter than the foreground. This filter preferentially inhibits light from the bright sky, allowing the foreground to appear brighter. The overall effect is to even out the exposure throughout the frame.

In this retrospective study, we identified 16 patients with cutaneous vascular disorders who visited the dermatology clinic of Hanyang University Hospital between June 2014 and May 2015. All patients were of Fitzpatrick skin types III and IV. Patients for whom standardized photographs were obtained before and after treatment were considered eligible for inclusion. Patients with a history of deep vein thrombosis, connective tissue disease, predisposition to hypertrophic scars and keloids, oral isotretinoin in the previous 2 months or immunosuppression, or who were pregnant or lactating were excluded.

All patients underwent a single treatment session using a long-pulsed Nd:YAG (Multiflex, Ellipse A/S®, Denmark). Surface cooling was achieved using a focused stream of cool air (SoftCoolTM) to reduce pain during treatment and to minimize the risk of possible epidermal damage. To treat vessels with a diameter of 0.2–0.3 mm, the following treatment parameters were used: 12.0 ms pulse width and 214.2–260.3 J/cm2 of fluence using a 1.5 mm spot. Larger dilated vessels with a diameter of 0.3–0.5 mm were treated with a pulse width of 16.0 ms and 225.1–252.2 J/cm2 of fluence using a 3.0 mm spot. When the vessel was treated with the laser, the immediate vessel response was carefully tracked. If the vessel disappeared immediately, the next laser shot was applied at the point where the vanishing point stopped. If the vessel did not show any response after the first shot, the fluence was raised to the next level (10–20 J/cm2 higher in general) and the laser firing point was moved up by about 1–2 mm from the initial spot to avoid stacking of laser pulses.

An RGND filter is a slight but significant variation on the GND. A RGND is darkest about 1/3 of the way from the top of the filter. It gradually gets less dark towards the top but not completely clear. It also gets gradually dark towards the bottom and does become completely clear. This filter is best used when the brightest part of the sky is near the horizon.

How many stops ND filter for video

Perhaps the least used variation of the ND filter is the CGND filter. It is dark in the center and gradually becomes clear at its periphery. This filter is used to counteract the peripheral darkening (vignetting) that can occur when certain lenses are shot at very large apertures.

Patient’s satisfaction: 1 = not satisfied, 2 = little satisfied, 3 = somewhat satisfied, 4 = satisfied, 5 = very satisfied.

Long-pulsed neodymium:yttrium-aluminum-garnet (Nd:YAG) lasers have recently been used for treatment of large, deep vascular lesions refractory to conventional vascular lasers. The aim of this study was to evaluate the clinical efficacy and safety of long-pulsed Nd:YAG laser treatment of various vascular disorders.

Several lasers emitting in the green and yellow range of the light spectrum, such as 585 nm and 595 nm pulsed dye lasers (PDLs), the 532 nm KTP laser, and the 578 nm copper vapor laser, are standardly used to treat various vascular disorders including port wine stains, superficial hemangioma, and telangiectasia.1,2 Intense pulsed light (IPL)-emitting noncoherent broadband light is considered to be an effective treatment option for diverse vascular lesions.3 However, this treatment modality tends to be less effective for deeply-situated vascular lesions than superficial vascular lesions due to the limited penetration depth of light.4

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Seven of 14 patients (50%) showed excellent improvement, six patients (42.9%) showed good improvement, and one patient (7.1%) showed moderate improvement. The average PGA score was 2.43 (Table 1, Figs. 1, 2).

Some popular ND strengths are three, six, and ten stops. It is also possible to combine (stack) filters to increase the overall strength. For example, combining three- and six-stop neutral density filters will result in nine stops of light inhibition. This works great in a pinch but should be avoided, if possible.  Each layer of glass or resin in front of the lens will degrade overall image quality. This could be the softening of details, color shifts, chromatic aberration to some degree.  The general principle is to use as few filters as possible to achieve the desired effect.

Patients were generally satisfied with the cosmetic outcomes of their treatment. Mean score was 4.0, and 10 of 14 patients stated that they were ‘very satisfied’ or ‘satisfied’ with their appearance. The boxes of ‘somewhat satisfied’ and ‘little satisfied’ were checked by one of the patients who experienced adverse effects (Table 1).

A VND filter allows you to change the strength of the filter based on how much it is turned. Videographers find this filter very helpful for achieving a “cinematic” look that is dependent on certain shutter speeds based on frames per second. In varying light, it’s more convenient to simply turn a filter in front of a lens than replace it periodically. Personally, I do not recommend it for photography. I’ve seen cross-type and patchy artifacts when doing long exposure photography.

In this study, we investigated the clinical efficacy, side effects, and subjective satisfaction of Korean patients after they underwent long-pulsed Nd:YAG laser treatment for diverse vascular disorders.

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What are neutral density filtersfor photography

If you’re a photographer trying filters for the first time, I recommend carrying a polarizer and a six-stop ND filter.  The polarizer will help you minimize glare from reflective surfaces. Be careful, however, when using it with ultra-wide angle lenses. If you include the sky in your field of view, a polarizer may cause some uneven color saturation.

Neutral density filters are also popular with portrait photographers. To achieve a beautifully creamy bokeh and a very shallow depth of field, the aperture needs to be wide open.  Some lenses can open to f/0.95. Even at the lowest ISO and fastest shutter speed, there might still be an overabundance of light to achieve proper exposure. An ND filter can help mitigate this problem.

If you decide to use round screw-on filters, I recommend purchasing one (or a set) that fits your largest diameter lens. If you want to use these filters on other smaller lenses than you only need to purchase a step-up ring instead of purchasing a new filter or set of filters.

There are several possible causes for the steep fluence-response curve of Nd:YAG laser treatment. When blood is heated to 50–54°C, partial oxidation of oxyhemoglobin leads to met-hemoglobin (met-Hb) formation.7,10 Optical absorption by met-Hb is much higher than that of either Hb or hemoglobin.11,12 Several in vitro studies13,14 have demonstrated that when blood is photocoagulated by 1064 nm Nd:YAG laser pulses, absorption at 1064 nm increases on the millisecond time scale by a factor of about 3, which may be due to partial conversion of oxyhemoglobin to met-Hb. When the lumen is thermally coagulated, optical scattering is increased and formation of a coagulum results in concentration of chromophores.1 In summary, long-pulsed Nd:YAG laser irradiation can heat up the entire vessel wall and coagulate the vessel at high fluence, which aids in the clearance of vascular lesions, unlike PDL and IPL.

GND filters are available in soft, medium, and hard varieties. On a “hard” GND filter, the transition between the darkest and clearest portion of the filter is abrupt. With a soft GND, the transition is much more subtle and spread out. With a medium GND, the transition rate is somewhere in the middle.

The most common side effects were erythema and vesicles in four of 14 patients (28.6%). Among these four patients, two reported mild post-inflammatory hyperpigmentation on the side that they received long-pulsed Nd:YAG laser treatment. However, those cutaneous reactions showed improvement without scarring (Fig. 3). No unbearable pain was noted in this study, and all patients tolerated the treatment well.

Step-up rings are considerably less expensive than optical filters. For example, if you own lenses with filter thread sizes of 67mm, 72mm, and 82mm, I recommend buying 82mm filters along with 67-82 and 72-82 mm step-up rings.

Neutral densityfilter Ophthalmology

There is a clear demand for laser treatment of various vascular lesions, but there are still challenges when using laser energy in a therapeutic context. PDL and IPL are used to treat superficial vascular lesions, but are not ideal for treating deeper lesions.3 With the advent of lasers with longer pulse durations and wavelengths than those used for PDL and IPL, deeper and larger caliber vessels can be managed more effectively without frequent treatment sessions and side effects. Long-pulsed Nd:YAG laser treatment of deeper vessels has been shown to be effective; however, the long-term effects of this laser treatment have not been evaluated.4 In this study, we demonstrated that diverse vascular lesions responded favorably to long-pulsed Nd:YAG laser therapy. As expected, we found that selective photothermolysis of vessels in vascular disorders including erythema, telangiectasia, port wine stain, cherry angioma, and hemangioma could be achieved by 1064 nm Nd:YAG laser pulses. Both PGA scores and patient satisfaction ratings after laser treatment were good. Long-pulsed Nd:YAG laser therapy can therefore potentially be used to treat both superficial and deep vascular disorders.

ND filter chart PDF

You may not think of a polarizer as an ND filter, but it does inhibit about 1.5–2 stops of light from entering the lens. A polarizer must be engaged (turned) to harness its “polarizing” properties (removing glare from reflective surfaces thus increasing saturation and contrast). However, this is not necessarily needed to utilize its ND property.

A six-stop neutral density filter is good to have with you for bright conditions when you want to blur out flowing water or convey a sense of motion to clouds.  If you need a little more stopping power, you can always stack it with the polarizer.

Clinical assessment was done by two blinded clinicians using Physician Global Assessment (PGA) based on evaluation of pre-treatment photographs and post-treatment photographs taken 1 month after the last treatment. Improvement was assessed on a scale from 0 to 3 (0 = no improvement, 1 = moderate, 2 = good, 3 = excellent). In addition, patients were asked to rate their satisfaction with the cosmetic results (1 = not satisfied, 2 = a little satisfied, 3 = somewhat satisfied, 4 = satisfied, 5 = very satisfied). Side effects after treatment were also assessed.

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Nevertheless, we demonstrated that long-pulsed Nd:YAG laser treatment is an alternative treatment modality for various vascular problems recalcitrant to standard therapy. Our study could also contribute to the establishment of appropriate treatment parameters. It is important to note that the use of bulk skin cooling, no overlapping of pulses, use of subpurpuric fluences, and use of a small spot size can limit dermal injury and improve the safety of Nd:YAG lasers. Further studies comparing the effects of variations in each of the treatment parameters or different treatment intervals should be performed to determine optimal treatment conditions.

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ND filters come in round and quadrilateral formats. Generally, round filters screw on directly to the front of your lens — if your lens has filter threads. I say “generally” because sometimes the front element is so big that it would be impractical to have a filter with such a large diameter. Instead, “drop in” filters are used at the back of the lens, near the camera’s lens mount.

Fourteen Korean patients underwent a single treatment session using a long-pulsed Nd:YAG laser. Two blinded clinicians rated cosmetic outcomes using ‘Physician Global Assessment (PGA)’ based on standardized photographs. Patients’ subjective satisfaction and side-effects of treatment were evaluated after treatment.

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Among 16 enrolled patients, two patients dropped out for personal reasons unrelated to the treatment. The remaining 14 patients completed this study. Patients’ age ranged from 16 to 62 years (mean, 45.4 years). Subtypes of vascular disorders were facial telangiectasia, rosacea, port wine stain, hemangioma, cherry angioma, and acne erythema. Detailed demographic information is provided in Table 1.

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Simply put,  neutral density (ND) filters are a piece of dark glass or resin that inhibits light from entering a lens. The “neutral” in neutral density refers to the fact that, theoretically, the filter is colorless. Basically, an ND filter is sunglasses for your lens. In this guide, we will be explaining the different kinds of neutral density filters and how to choose the best one to fit your photography needs.

Long-pulsed Nd:YAG laser treatment is a safe and effective treatment modality for diverse vascular disorders that are unresponsive to conventional therapy.