Nikon D7100+Sigma 300F2.8+TC1.4
Hello Everyone,
I am sorry if this this thread was already posted but being new to this forum, I could not find any other better option
Current I am owning Nikon D7100 along with Sigma 300mm f2.8 lens. Though the camera gives me 1.3x crop factor to my existing 300mm lens, how it will be if I add sigma 1.4X TC.
My question is, will I loose the sharpness of my object or is good to have both (TC and 1.3x crop factor) while taking photos. My interest is in bird photography
The crop factor of the camera will only affect sharpness in that it gives you a 390mm focal length, and with the 1.4 TC you then have 546mm. So you will need to be more careful with camera shake and subject movement in order to get sharp pictures. And depth of field will be smaller at longer focal lengths, so getting the focus point exactly where you want it is more critical.
The camera might also have more trouble with focus on a moving subject, such as a bird in flight, since the 1.4X will cause a stop of light loss.
But with these factors aside, the 1.4x should cause a negligible loss of sharpness, especially in the center. It is more likely to introduce some subtle vignetting and some chromatic aberration, which can be compensated for in processing.
Having longer focal lengths (more pixels on the subject) is better than cropping.
thanks, looking at your reply, TC is better than the crop factor since i will loose sharpness and MP if I go with 1.3 cro factor?
You can't really compare them as you already have the crop factor -- or is it an in-camera option? (I don't know the camera.) If it is an option, the way some pocket cameras have "digital zoom", it will cause some degradation in images by giving you less pixels. If you are comparing the crop body without the TC to a full-frame body with it, you are probably about equal with either case. The crop body was designed to give best quality at its size.
Originally Posted by sudarmani shanmugham
I use(d) the Sigma Prime and the Sigma 1.4x on my D300, and found that IQ was only marginally degraded when comparing images taken with and without the converter.
The In-camera crop option offered by some models now is, as far as I understand it, just good to get smaller file sizes to begin with, since you will not get more pixels per area.
Cropping the full size file later on the computer will yield the same result.
With the TC you get an enlarged image on the sensor, i.e. more pixels/detail per subject surface area, favorable as long as the TC isn't degrading IQ too much.
My 0.02
Ulli
thanks Ulli . It was of great help, after browsing through, i have decided to go with TC but now i am confused between 1.4x or 2x though 2x would give me f5.6
Also, i dont know why but i am not able to focus small birds sitting on a moving branch.. by the time my 7100 focus, it fly away... can you help.. i kept the camera in appeature mode with auto ISO and spot metering... anything i am missing out?
The camera mode (Aperture or whatever) and metering mode (spot or whatever) won't have an effect on focus. You need to select one focus sensor and have it on the most important part of the image (the head and eye). I don't know what Nikon calls it but if everything is still you can use the appropriate focus mode. If the subject is moving, or you are hand-holding, you should be in the continuous focus mode. You will need to be very steady if you are hand holding.
That lens is very "fast" with the f/2.8 aperture as it focuses. (It only stops down to take the picture.) So if the speed of AF isn't fast enough, and you are able to keep one active focus sensor on the subject, the fault may be with the camera body. But as lot of people here use it so I suspect it is good.
How small are the birds in the viewfinder?Are you not able to get it in focus at all, or are you unable to keep it in focus?
Dianne already pointed out that you want just one active focus sensor and continuous focus mode (AF-C). Tricky part is usually to keep the focus sensor on a small subject (here a monopod can be very supportive). Once you aim past the bird other contrasting structures in fore- or background will become more attractive for the focus system and it will start hunting for those. Somewhere in your AF menu should be a setting that will allow you to determine how long AF-C waits before refocusing after loosing contact with a subject. I keep that AF-C delay in the medium-long range if there is a lot of other moving stuff like grass or branches that may get temporarily between me and the subject , so if I can't keep the focus point on the target for a brief moment I have a brief moment to re-aim before the camera starts hunting for focus.
I tried the Sigma 2x, didn't like it as IQ suffered visibly. I have seen people getting good results with 2x converters, so maybe mine was a lemon. However, with a 2x your AF-speed will dramatically decrease and focusing gets too slow for many situations.
Ulli
I have that lens and use it in Pentax mount. I just came back from a fun time shooting with it and the Sigma 500mm F/4.5 lens. I personally do not use it with a 1.4 teleconverter. I find it does not hold up to my standards. For lack of a better word it is a dog. Without a T.c. I like it ok. If that were the only problem with the lens I would really like it. Mine has a focus shift adj problem. Just a pain for critical work.
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