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Forum: Pentax News and Rumors
04-07-2024, 08:25 PM
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One of the latest cameras that I have seen like the D850 D5 and D6 still use a mask of at least ƒ6
---------- Post added 04-07-2024 at 08:36 PM ----------
Much of this has to do with precision of phase detection, not how much light is passing the mask
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Forum: Pentax News and Rumors
04-06-2024, 12:55 PM
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The separator mask limits the area from which the AF sensor gathers light this is needed to detect phase shift
"The primary result from this demonstration, is that the brightness of the images on the AF sensor is unchanged (other than the slight vignetting mentioned above). This demonstrates that none of the extra rays from opening the lens wider than f/7.5 are arriving at the AF sensor."
Autofocus System Design
No this does not mean that faster lenses don't AF faster, most faster lenses are more expensive then the much slower lenses thus more expensive Af motors and more RD go into making the AF as a system work faster.
Using my 300 2.8 with all of the Pentax cameras I used that lens with the aperture lever removed such to be used to correct for focus shift, with the lever removed the lens would be only as wide as the aperture ring was set.
There was no difference to how well or quickly the lense focused until I reached the limit of the separator masks found in the AF sensor this was around f 6 for most of the pentax cameras that I have used. some Canons I are around F4
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Forum: Pentax News and Rumors
04-05-2024, 11:22 PM
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It really depends on the separator mask found in front of the AF unit, This will limit the amount of light that would reach the sensor if the mask is F5.6 then no more light coming in from the lens will not make it to the sensor even if it is a F1.8
Most masks limit to around ƒ 6 to ƒ7.5
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Forum: Pentax DSLR Discussion
03-21-2024, 09:57 PM
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Sure it does, the practical implications are that they would capture the same amount of light
So it is important that you have the ability to get a shot that will be noisier, there is also a very important point that has to be made that it can be done with the F4 lens which happens to be not much heaver or larger than the 50-135.
If your goal is to have a lighter lens at the cost of light gathering the why would a FF users look at using the 70-200 2.8. As a FF user I went with the 70-200 F4 for the very reason why I did not need the 70-200 2.8 for the majority of my work while reducing my weight.
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Forum: Pentax DSLR Discussion
03-21-2024, 09:01 PM
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But that 70-200 2.8 does a different job than the 50-135 2.8 that extra stop of light comes at a cost.
When compared to a similar lens that does similar job most FF lens do the same job are only 130g -160g heaver with most of them including a form of VR
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Forum: Pentax DSLR Discussion
02-18-2024, 02:23 AM
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It was not ETTRed the one image was under exposed by nearly 3 stops
But closing the gaps will change the tonal value of your colors also. I will repeat this there is only 3 stop difference between white and middle grey and not 5 stops. Zones 9 and 10 are tonal values that are not white but lighter than white, spectral highlights and light sources as described in Ansel's Zones. Remember these are measurements from middle grey and white spectral highlights (zone10) of course much brighter than white because they are basically a reflection of the light source pointed at the camera.
Here are the measured values of a color checker target, the white patch on the target measures as LAB 96,54 -0,425 1,186 that put it at 95% or 2.5 stops from middle grey. White with a 100% will put it at Lab 100 that is 3 stops from middle grey. there is no 5 stops. So what are you trying to compress ?
If you don't believe me that the white target is 2.5 stops from MG all you have to do is decrease your exposure by 2.5 stop mechanically with your camera and that white target is now middle grey.
If white 9.5
neutral 8
neutral 6.5
neutral 3.5
black 2
Do not hit there targeted lab values that means your yellow wont hit L81.73 , your red won't hit L42.10 and your orange won't hit 62.66 so of course they won't hit the correct tonal range as your correctly exposed image it is as simple as that.
Your white 9.5 has to be 9.5
your neutral 8 has to be 8
your neutral 6.5 has to be 6.5
your neutral 3.5 has to be 3.5
and your black 2 has to be 2 or everything will not be correct.
So are we shocked that everything else looks off when you are trying to compress everything?
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Forum: Pentax DSLR Discussion
02-15-2024, 02:58 PM
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You do not have to create a new tonal curve for this.
here is an image that was ETTR at 0.5 sec
here at 1/3 sec
and at 1/10 sec
The light source remained the same
that is 2 1/3 of a stop difference in exposure and not once did I change the curves
Here is an overlay of the color checker patch the bottom image is the under and the overlay is the 2 1/3 over that base exposure
There should be no need for you to create a new curve all that was done was shown in the ARC settings
---------- Post added 02-15-2024 at 04:05 PM ----------
Here I have applied a different tonal curve but the same curve was applied to both shots
And again the top is exposed 2 1/3 stops more the base
---------- Post added 02-15-2024 at 04:22 PM ----------
Here is the same image processed using silkypix using the same curve for both
And again, the top was taken with an exposure that was 2 1/3rd stops brighter
This was done very quickly and only adjust for the difference in the number of stops and not the lightness of the final image.
There could a slight difference in the accuracy of those exposures over that 2 1/3 variation
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Forum: Pentax DSLR Discussion
02-15-2024, 01:23 PM
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Yes but in zones 9 and 10 those are not representing white, they are objects that when measured from middle grey are 4 to 5 stops lighter than middle grey and are 1 and 2 stops brighter than white.
---------- Post added 02-15-2024 at 02:32 PM ----------
It is about processing. How light or dark the image is not a function of exposure, how light or dark an image is a function of processing. Any clipping of data will produce incorrect colors and tonal values when processed.
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Forum: Pentax DSLR Discussion
02-15-2024, 01:22 AM
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It is because Zone X was never about being white, it was about being brightest portion of a scene. Snow and spectral highlights while they appear as white they are 1 to 2 stop brighter than white.
White is and never has been 5 stops above middle grey
Zones 0-X are how the brightest objects appear and how many stops away from middle grey they read. Look at what people place in the scene and what objects fall within those zones.
A very simple test, take a calibrated white target that is as close to white as you can get, spot meter on that target with a +2 2/3 ec, take a photo, that white target should fall very close to white in jpeg file. Now cut the light by that 2 2/3rds with your shutter speed.
If white is truly 5 stops from MG then that white target would not be close to middle grey but it is. I reduce the light by 2 2/3 stop and it is now middle grey this should convince you that it is only +- 3 stops from middle grey
So what is in zone x, specular highlights, Light sources and so on.
Place a specular highlight like a mirror or a piece of steel reflecting your light source at the camera it is much brighter than your white target.
Zone IX glaring snow,
It projects 1 -2 stops more light than your white target. Snow is not white it has many tiny spectral highlights with spaces between those highlights thus reducing the density of the light but nonetheless still produces a value greater than white.
The very same with clouds and water droplets they can be much brighter than white
The very same reason why we get sunburnt and Snowblind from snow as the it is reflecting 2-4 times greater than white. Now Place you white target beside the very same snow it will not appear as bright as it in not reflecting as much light.
---------- Post added 02-15-2024 at 02:34 AM ----------
It is never possible to replicate the specular brightness of zones X-IX in print as it is beyond what we can display in print ( as this is what our colorspaces designed for) or on the monitor as the whitest we can create is the whiteness of the paper. For us to simulate we would have to cutout the specular highlights in the photograph and apply a light from behind our image that is equal to the brightness that we want to recreate in that highlight.
Now with zone photography we can use ETTR to save what highlights we want and compress them into the medium we are going to display them as a pleasing image.
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Forum: Pentax DSLR Discussion
02-13-2024, 01:45 PM
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It depends on the color space
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Forum: Pentax DSLR Discussion
02-13-2024, 12:38 PM
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Forum: Pentax DSLR Discussion
02-12-2024, 11:03 PM
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My response was more about how to get the correct reading for setting the WB. If I place a WB card within the frame of what you are shooting not having the WB card perpendicular to your light source will produce a different WB than one that is perpendicular.
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Forum: Pentax News and Rumors
02-12-2024, 08:36 PM
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It is kind of a blessing and a curse.
Used Nikon DLSR and lenses have tanked It is not hard to find DLSRs 36 and 46mp bodies combine that with a 70-200 2.8 and 24-70 2.8 can all be had for under $3000 with 3 year warranty
Until these are gone is when we see a migration to Pentax
We also don't see the lenses that would also persuade Nikon users as they are accustom to a verity of fast primes
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Forum: Canon, Nikon, Sony, and Other Camera Brands
02-12-2024, 03:38 PM
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Pixel density at very low light levels can play a role but it has more to do with what the sensors was designed to do.
How the sensor is used by the camera manufacture can also play a role in how it performs.
The main factors are how much light the sensor records this determines the shot noise, how the sensor is use this can determine the read noise.
How much light can vary based on how the sensor is used most sensor with smaller pixel can store more light over the total area of the sensor ( this is why some cameras can use lower iso than 100)
Sensors that are designed for lower readnoise tend to suffer at the base DR but excel at higher than normal iso.
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Forum: Pentax DSLR Discussion
02-11-2024, 04:38 PM
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One of the first problems is what is the correct white balance?
If was to use a WB card, how I place that card in the scene there would be numerous WB readings you can obtain.
If you are going for accuracy for the temp of the light source then the WB for that source would only be correct for any white or color object that is perpendicular to that light source. Any object that is not perpendicular will have a color cast introduced from surrounding objects.
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Forum: Canon, Nikon, Sony, and Other Camera Brands
02-11-2024, 12:19 PM
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If you look at what Nikon is doing, it is something like $400,000,000 in R&D that is rather a large amount of investment and they are still making money. Granted all of that is not in Imaging but still this shows Nikons not in the gloom and doom state of disappearing anytime soon.
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Forum: Canon, Nikon, Sony, and Other Camera Brands
02-08-2024, 02:27 PM
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You can spit out Pentax PS images into a single DNG with most PS converters. this then can be used on almost any raw converter, create color profiles and any other raw converter applications
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Forum: Canon, Nikon, Sony, and Other Camera Brands
02-08-2024, 01:26 PM
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But you are still only limited to using Raw therapee or only raw converters that are up to date or support PS.
I have no problem using even my 2011 ARC for raw file that are combining PS via software into a raw file and then run in most any raw converters.
SonyPixelShift2DNG combines a7R III Pixel Shift shots into DNG files: Digital Photography Review
"As the name implies, this piece of software combines the four ARW files captured by your Sony a7R III in Pixel Shift mode and spits out a DNG on the other side, allowing you to process the result in the Raw editor of your choice"
There are other software out there that allow you to do this also, I even use this kind of feature for image stacking, run it thru the software and it spits out a raw file for any raw converter to use
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Forum: Canon, Nikon, Sony, and Other Camera Brands
02-08-2024, 12:30 PM
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There can be benefits to combining them after,
You can combine them into a raw file that is then compatible with almost any raw converter without that raw converter needing to be compatible with pixelshift.
I like using these kinds of software, its easy to create color profiles and just easy for raw converters
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Forum: Troubleshooting and Beginner Help
02-07-2024, 02:27 PM
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I would first look at how you are going about polar alignment, one of the easiest I found is to use an app
?Polar Scope Align on the App*Store
I would then be looking how you setup the tripod, I would recommend if possible on a stable surface like gravel or a packed surface, if shooting on grass take a shovel and remove the first layer of grass until you get to solid earth. The movement of the tracker can shift the weight of the setup and tilt the rig.
Next look at balancing the tracker with the camera this can be easy to do just adjust the counterweight until it spins freely and easily with the clutch disengaged.
Look at how much travel you have as either the camera or the counterweight could come in contact with the tracker, tripod or any cables you may be using.
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Forum: General Talk
02-07-2024, 12:21 AM
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The wavefront gets compressed when the material slows the light, for the wavefront to stay connected it has to change direction at the boundary of the material it is passing through.
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Forum: Photographic Technique
02-06-2024, 01:55 PM
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You beat me to this video
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Forum: Troubleshooting and Beginner Help
02-05-2024, 12:11 AM
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I would first start of by managing your exposure a little better, with such a high shutter speed you need to raise the iso to a point that can cause issues with noise.
I would look at using a slower shutter speed to increase the amount of light which would decrease the iso you would use.
Next by looking at the image i would appear about a 1/2 a stop or more under exposed ( too dark)
Here I have lightened the image by 1 stop
Here I added more contrast to the image
Next I would look at your light source, for capturing details wood you want to use a light source that introduces textures of the wood grain. 1 to 2 light sources setup such that they won't introduce reflections but create the textures from the wood.
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