الان canon 60D یا نیکون D7000 از این کارتها پشتیبانی نمی کنند؟
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چند روز پیش بحثی شد تو این تاپیک:نقل قول:
سرعت نوشتن اطلاعات روي كارتهاي SD با كلاسn مشخص مي شود:
Class 2: 2 MB/s
Class 4: 4 MB/s
Class 6: 6 MB/s
Class 10: 10 MB/s
http://www.akkasee.com/forum/showthr...ht=#post181346
دوستی میگفت که :
اعداد کلاس ربطی به سرعت نوشتن و خوندنشون ندارن
آیا این اعداد کمترین سرعت رایت است؟
اگر اینطور است سرعت رایت می تواند خیلی بالاتر از این باشد؟(بطور مثال دو برابر)
می توان کاری کرد که اطلاعات حذف شود و قابل بازیابی نباشد.نقل قول:
چون در عمل شما بعدا هم نباید مموری یا هارد دیسکی که استفاده شخصی کردید رو بفروشید (به این دلیل که مموری دست دوم اطلاعاتش قابل بازیابی است).
به نقل از سايت سن ديسك:
Difference between Speed Class and Speed Ratings (performance) for SD/SDHC cards What is the difference between Speed Class and Speed Ratings for SDTM/SDHCTM cards? The speed rating measures maximum transfer speed for writing and reading images to and from the card, expressed as megabytes per second. However, video doesn't need as big a pipe because the video format is a smaller "fixed stream" that uses only a portion of the pipe.
Unlike card write speeds that measure maximum performance, class ratings measure the minimum sustained speed required for recording an even rate of video onto the card. The class rating number corresponds to the transfer rate measured in megabytes per second. Class 2 cards are designed for a minimum sustained transfer rate of 2 megabytes per second (MB/s)1, while Class 10 cards are designed for a minimum sustained transfer rate of 10MB/s2.
What does this difference mean for me?
Rated Speed (e.g. 15MB/s, 30MB/s, etc.) is maximum speed of the card and also what you would expect to approximately see in typical usage of writing or reading files on the card. This measurement is pertinent to still photography, especially for taking pictures with high resolution and/or saving in RAW format where the files created are very large. The faster the card, the faster it can save the file and be ready to take another picture. You really notice speed differences with high-megapixel DSLR and multi-shot burst mode.
Still digital images shot on high-megapixel cameras should utilize fast data throughput (a large pipe), higher speed cards for improved performance. Higher speed cards can also improve how fast you can download (or upload) the files from the card to your computer.
Speed Class is a minimum speed based on a worst case scenario test. The Speed Class is important for video mode or camcorders, where the device is actually saving a steady stream of data. The resolution and format of the video determines the amount of steady stream data. This translates to a minimum speed you need to guarantee that the video captured on the cards is recorded at an even, sustained rate with no dropped frames (which typically results in lost data and choppy playback).
Compared to high-megapixel photography, video doesn't need as big a pipe because the video format is a smaller "fixed stream" that uses only a portion of the pipe. But you do need a minimum guaranteed speed for the SDHC card that satisfies the requirement of the data stream. Your camera's specifications should state the minimum SDHC Class Rating required.
Using a card without the proper class rating on a more advanced camera, such as a high-definition (HD) camcorder or Digital Single Lens Reflex (DSLR) camera with HD video record settings is likely to result in an error message indicating that video can only be recorded at a lower definition setting.
The current SDHC specification defines Class 2, 4, 6, 8 and 10 as follows:
Class
Minimum Speed
2
2MB/s
4
4MB/s
6
6MB/s
8
8MB/s
10
10MB/s
1 1 megabyte (MB) = 1 million bytes
2 Based on SanDisk internal testing; performance may vary depending upon host device.
سلام
البته اعتماد یک مساله شخصی است :) , مثلا ً خود من تا حالا 2 بار کول دیسک ترنسند خریدم که هر دو بار بدون دلیل خاصی سوخته اند , اما
توشیبا به همراه پاناسونیک و سندیسک , کارت SD را به وجود آوردند و هر سه ؛ بنیانگذاران موسسه SD Card Association (موسسه مستقلی که استانداردهای این کارت را وضع میکند) هستند.
نقل قول:
Secure Digital (SD) is a non-volatile memory card format developed by Panasonic, SanDisk, and Toshiba for use in portable devices
__________________________________________________ ___کد:http://en.wikipedia.org/wiki/Secure_Digital
http://en.wikipedia.org/wiki/SD_Card_Association
http://www.sdcard.org/home/
بله, این سرعتها , حداقل سرعت نوشتن روی کارت باشد
نقل قول:
This table lists common ratings and minimum transfer rates....
SDHC cards also feature minimum speed class ratings. A Class 2 card has a minimum sustained write speed of 2MB/s; Class 4: 4MB/s, and Class 6: 6MB/s.
.....
..
The Speed Classes define three minimum sustained write speeds in next generation SD Cards. Class 2 supports a minimum write speed of 2 megabytes (MB) per second*; Class 4 supports 4MB per second; and Class 6 supports 6MB per second. The SD Speed Class is shown as a "C" with a numeral inside, on the card and its packaging, above and to the right of the capacity rating. For example, the standard Toshiba SD Card on the left meets Speed Class 4, and the High Speed SD Card, right, is rated Speed Class 6.
http://www.toshiba-memory.com/img/lo...d_classes2.jpg
به عنوان مثال کارت خودم , کلاس 4 , سرعت رایت تا 10 مگابایت بر ثانیهکد:http://www.toshiba-memory.com/en/what_is_sdhc.html
http://en.wikipedia.org/wiki/Secure_Digital#.C3.97_rating
100% همينطوره وحيد عزيز :redface:
البته من هم الان اون اعتمادي رو كه 2 سال پيش به ترنسند داشتم ديگه ندارم (هرچند خودم تا به حال مشكلي با هيچ يك از محصولاتش نداشتم ولي اينجا و اونجا گزارش هايي شنيده ام) و به همين دليله كه چون معتقدم آدم همه ي تخم مرغ هاشو نبايد توي يك سبد بذاره براي G11 مموري توشيبا خريدم ولي اين هم خيلي قابل اعتماد نيست.
سلام خدمت تمامی دوستان و اساتید عزیز
بنده میخوام مموری cf بخرم
که دونوع دیدم یکی بقوله خودمو معمولی بود فکر میکنم باسرعت 60 مگ و یکی دیگه بود UDMA یادم نیست چه سرعتی!
فرق معمولی با UDMA چیه و کاربردش کجاهاست؟!
ببخشید که زیاد سوال پرسیدم
ممنون